F5 Networks 301a – LTM Specialist: Architect, Set-Up & Deploy
Study Guide
Version 1 - TMOS 11.2
Eric Mitchell
Channel SE, East US and Federal F5
Networks
12/31/2014
e.mitchell@f5.com
F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Overview
Welcome to the 301a - LTM Specialist compiled Study Guide. The purpose of this guide
is to help you prepare for the F5 301a - LTM Specialist exam. The contents of this
document are based on the 301a - LTM Specialist Blueprint Guide.
This study guide provides students with some of the basic foundational knowledge
required to pass the exam.
This study guide is a collection of information and therefore not a completely original
work. The majority of the information is compiled from F5 sources that are located on
Internet. All of the information locations are referenced at the top of each topic instead
of in an Appendix of this document. This was done to help the reader access the
reference the linked information easier without having to search through a formal
appendix. This guide also references the same books as the exam Resource Guide for
each topic when applicable for consistency.
F5 Networks provides the 301a - LTM Specialist Resource Guide as a study guide. The
Resource Guide is a list of reading material that will help any student build a broad base
of general knowledge that can assist in not only their exam success but in becoming a
well rounded systems engineer. The Resource Guide will be available to the candidate
once they are qualified for the 301a - LTM Specialist exam.
Taking certified F5 LTM training, such as Administering BIG-IP v11 and Configuring BIG-IP
LTM v11, will surely help with the topics of this exam but does not teach directly to the
exam content. Hands on administrative experience with the Big-IP platform licensed
with LTM will reinforce many of the topics contained in the 301a - LTM Specialist exam.
The F5 Certified Big-IP Administrator (F5-CA), which is made up of the 101 - App Delivery
Fundamentals and 201 - TMOS Administration exams, stand as a pre-requisite to this
exam.
This guide was prepared by an F5 employee but is not an official F5 document and is not
supported by F5 Networks.
Reading = Knowledge = Power
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Contents
Overview ................................................................. 2
Contents .................................................................. 3
Printed References.................................................. 6
Introduction ............................................................ 7
Section 1 – Architect an application ....................... 8
Objective - 1.01 - Given an expected traffic volume, determine the appropriate SNAT
configuration ........................................................... 8
Objective - 1.02 - Given a scenario, determine the minimum profiles for an application
............................................................................... 11
Objective - 1.03 - Given an application configuration, determine which functions can be
offloaded to the LTM device ................................. 20
Objective - 1.04 - Given an iRule functionality, determine the profiles and configuration
options necessary to implement the iRule. .......... 25
Objective - 1.05 - Given an application configuration, determine the appropriate profile
and persistence options ........................................ 27
Objective - 1.06 - Explain the steps necessary to configure AVR 31
Objective - 1.07 - Given a set of reporting requirements, determine the AVR metrics and
entities to collect .................................................. 36
Objective - 1.08 - Given a scenario, determine the appropriate monitor type and
parameters to use ................................................. 39
Objective - 1.09 - Given a set of parameters, predict an outcome of a monitor status on
other LTM device objects...................................... 46
Objective - 1.10 - Given a set of SSL requirements, determine the appropriate profile
options to create or modify in the SSL profile ...... 48
Objective - 1.11 - Given a set of application requirements, describe the steps necessary
to configure SSL .................................................... 50
Objective - 1.12 - Given a set of application requirements, determine the appropriate
virtual server type to use ...................................... 59
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Objective - 1.13 - Given a set of application requirements, determine the appropriate
virtual server configuration settings ..................... 61
Objective - 1.14 - Explain the matching order of multiple virtual servers
65
Objective - 1.15 - Given a scenario, determine the appropriate load balancing method(s)
............................................................................... 67
Objective - 1.16 - Explain the effect of LTM device configuration parameters on load
balancing decisions ............................................... 78
Section 2 - Set-up, administer, and secure LTM devices 86
Objective - 2.01 Distinguish between the management interface configuration and
application traffic interface configuration ............ 86
Objective - 2.02 Given a network diagram, determine the appropriate network and
system settings (i.e., VLANs, selfIPs, trunks, routes, NTP servers, DNS servers, SNMP
receivers and syslog servers) ................................ 95
Objective - 2.03 Given a network diagram, determine the appropriate physical
connectivity ......................................................... 101
Objective - 2.04 Explain how to configure remote authentication and multiple
administration roles on the LTM device ............. 103
Objective - 2.05 Given a scenario, determine an appropriate high availability
configuration (i.e., failsafe, failover and timers) 107
Objective - 2.06 Given a scenario, describe the steps necessary to set up a device group,
traffic group and HA group ................................. 113
Objective - 2.07 Predict the behavior of an LTM device group or traffic groups in a given
failure scenario ................................................... 120
Objective - 2.08 Determine the effect of LTM features and/or modules on LTM device
performance and/or memory ............................. 122
Objective - 2.09 Determine the effect of traffic flow on LTM device performance and/or
utilization ............................................................ 133
Objective - 2.10 Determine the effect of virtual server settings on LTM device
performance and/or utilization .......................... 135
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Objective - 2.11 Describe how to deploy vCMP guests and how the resources are
distributed ........................................................... 137
Objective - 2.12 Determine the appropriate LTM device security configuration to protect
against a security threat ..................................... 150
Section 3 – Deploy applications .......................... 157
Objective - 3.01 Describe how to deploy and modify applications using existing and/or
updated iApp application templates .................. 157
Objective - 3.02 Given application requirements, determine the appropriate profiles and
profile settings to use ......................................... 163
Objective - 3.03 Determine the effect of traffic flow on LTM device performance and/or
utilization ............................................................ 215
Conclusion ........................................................... 229
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Printed References
These referenced books are and important and should be considered basic reading
material for this exam. If you have a newer copy of the material that is fine, be aware
that the exam is based on the 11.2 version and content could have changed.
(Ref:1) Configuring BIG-IP Local Traffic Manager v11.2. v11.2.0 Edition. F5 Networks
Training Course Manual.
(Ref:2) Administering BIG-IP v11.2. v11.2.0 Edition. F5 Networks Training Course
Manual.
(Ref:3) Troubleshooting BIG-IP v11.2. v11.2.0 Edition. F5 Networks Training Course
Manual.
(Ref:4) Developing iApps for BIG-IP v11.2. v11.2.0 Edition. F5 Networks Training Course
Manual.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Introduction
F5 - 301a Local Traffic Manager Specialist Exam
The F5 BIG-IP Local Traffic Manager (LTM) increases an application’s operational
efficiency and ensures peak network performance by providing a flexible, highperformance application delivery system. With its application-centric perspective, LTM
optimizes your network infrastructure to deliver availability, security, and performance
for critical business applications. Although the Exam Blueprint is not written in a
structure that presents topics in an educational order, it does provide all of the
necessary building blocks. The Certified LTM Training classes from F5 will help with
many of the scenario-based topics on the test. An LTM Specialist must be proficient
with all aspects Architecture, Setup and Deployment of the LTM within a network.
Link to Online Topic Content
Traffic Management Shell
Although it is not mentioned in the blueprint as a requirement, a candidate should not
focus only on the GUI interface for management of the LTM platform. Some test
questions will refer to the command line interface (CLI) TMSH commands. You should
take time to understand where in the CLI that common commands are issued so you can
not only correctly answer the questions presented on the exam but also have enough
knowledge of the CLI structure to eliminate bad commands from your question’s answer
choices.
Try building your vLab environment from command line to gain CLI proficiency.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Section 1 – Architect an application
Objective - 1.01 - Given an expected traffic volume, determine
the appropriate SNAT configuration
1.01 – Explain when SNAT is required
Link to Online Topic Content
Link to Online Topic Content
What is SNAT and when is it required?
A Secure Network Address Translation (SNAT) is a configuration object that maps the
source client IP address in a request to a translation address defined on the BIG-IP
device. When the BIG-IP system receives a request from a client, and if the client IP
address in the request is defined in the origin address list for the SNAT, the BIG-IP
system translates the source IP address of the incoming packet to the SNAT address.
A SNAT can be used by itself to pass traffic that is not destined for a virtual server. For
example, you can use a SNAT object to pass certain traffic (such as DNS requests) from
an internal network to an external network where your DNS server resides. A SNAT can
also be used in conjunction with a virtual server to translate the source IP address of an
incoming packet (with no SNAT configured, no source address translation takes place,
and destination address translation takes place as separately configured in the Virtual
Server properties). You can also use a SNAT to ensure that response traffic is returned
through the BIG-IP system without requiring other outbound non-load balanced traffic
to also route through the BIG-IP system, and without requiring any changes in the
router or server's configuration. SNAT is also a critical component in one-armed
configurations, preventing the server from responding directly to the client.
Port exhaustion or collisions may occur under heavy usage or special client traffic
patterns. As a result, connections that cannot be translated due to lack of available
ports on a given translation address may be dropped.
When a SNAT is configured on the BIG-IP system (either by itself or in conjunction with a
virtual server), the source address of each connection is translated to a configured SNAT
address, and the source port is mapped to a port currently available for that address. By
default, the BIG-IP system attempts to preserve the source port, but if the port is
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
already in use on the selected translation address, the system also translates the source
port.
Each SNAT address, like any IP address, has only 65535 ports available. This is a limit of
the TCP and User Datagram Protocol (UDP) protocols, since they use a 16-bit unsigned
integer (thus ranging from 0 to 65535) to specify the source and destination ports.
However, each SNAT address can potentially have to process more than 65535
concurrent connections, as long as each socket pair is unique. A socket pair is defined
by a 4-tuple structure consisting of the following elements:




Source IP address
Source port
Destination IP address
Destination port
For example, a given SNAT address can continue to use the same source port as long as
the remote socket is unique, thus allowing the SNAT address to process more than
65535 concurrent connections.
For example:
SNAT address and port




Remote socket
10.1.1.1:1234 -------------> 10.1.1.200:80
10.1.1.1:1234 -------------> 10.1.1.201:80
10.1.1.1:1234 -------------> 10.1.1.200:8080
10.1.1.1:1234 -------------> 10.1.1.201:8080
Note: When SNAT is used in conjunction with a virtual server that load balances
connections to a pool; the remote socket is the IP address and port of the chosen pool
member. Therefore, assuming a certain SNAT address is configured on only one virtual
server, the SNAT address is able to process approximately 65535 concurrent
connections for each pool member in the pool (each unique remote socket).
While the uniqueness of remote sockets depends entirely on your specific configuration
and traffic, for simplicity you should think of 65535 concurrent connections as the
maximum capacity for any given SNAT address. If you think more than 65535
connections may require translation, you should configure more SNAT addresses (for
example, using a SNAT pool).
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
1.01 – Describe the benefit of using SNAT pools
Link to Online Topic Content
SNAT Pools
A SNAT pool represents a logical group of translation addresses that you configure on
the BIG-IP system.
When a single IP address is used to SNAT traffic, it has a limit of 65535 ports that can be
used for port mapping on the IP address. SNAT connections can fail if a large number of
client requests are traversing a SNAT, which is using a single IP address. This will show
up in the event logs on the BIG-IP as Port Exhaustion errors.
To mitigate port exhaustion, create SNAT pools or use SNAT Automap (with an
appropriate number of self-IP addresses on the VLAN) to support the expected level of
concurrent connections. Configuring a SNAT pool as the translation allows the SNAT
function to map client connections to more than one IP address from the SNAT pool,
thus increasing the total available ports likewise the supported client connections.
You can build a SNAT pool for a SNAT to use as the translation addresses and the BIG-IP
will use an IP addresses from the pool in a round robin fashion.
Since the SNAT function is intelligent enough to know what address from the pool can
be used for the address translation in each egress scenario; a SNAT pool can contain
addresses from more than one egress network. This will allow you to build less SNAT
pools by allowing you to mix the egress network addresses in one pool if you desire.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Objective - 1.02 - Given a scenario, determine the minimum
profiles for an application
1.02 - Given a scenario, determine the minimum profiles for an
application
Link to Online Topic Content
Scenario Based Questions
To prepare for scenario based questions the candidate will need to complete hands-on
configuration and testing of the configuration on the LTM. This will allow the candidate
to better understand how different configurations can produce different results. All F5
exams use scenario-based questions that make the candidate apply what they know to a
situation to determine the resulting outcome.
This topic is focused on assigning profiles to a virtual server configuration for the
functionality of application using that virtual server. Understanding how why profiles
are necessary and what requirements the applications have for the processing of the
application traffic is the key to this topic. Experience with configuring virtual servers
will give the candidate the ability to answer the questions on this topic.
The BIG-IP LTM can manage application-specific network traffic in a variety of ways,
depending on the protocols and services being used. For each type of traffic that you
want or need to manage, the LTM system contains configuration tools that you can use
to intelligently control the behavior of that traffic. These tools are called profiles. A
profile is a system-supplied configuration tool that enhances your capabilities for
managing application-specific traffic. More specifically, a profile is an object that
contains user-configurable settings, with default values, for controlling the behavior of a
particular type of network traffic, such as HTTP connections. Using profiles enhances
your control over managing network traffic, and makes traffic-management tasks easier
and more efficient.
A virtual server can be set with a minimum of a layer for protocol profile and traffic will
pass to the pool resource. Without profiles set to tell the virtual server how to process
that type of traffic it is possible that some necessary functions will not be able to be
completed.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
1.02 - Explain security options available for the application
Virtual Server Security
A virtual server is essentially a listener that will be taking in and processing traffic on the
BIG-IP platform. Some of the biggest security risks when configuring a virtual server are
how it is listening, where it is listening and who can get to it. If you are configuring
virtual server and not setting the necessary settings to restrict these areas of concern
you are opening your self up to security risks.
How Is The Virtual Server Listening?
The broader you set a virtual server to listen the greater the risk of unintended inbound
traffic. An application based virtual server should typically be configured to listen on the
default port for the application. For example if you are configuring a virtual server for a
new HTTP based website you would listen on port 80. If you listen on all ports (*), the
virtual server will take in traffic destine for the virtual server on all 65535 ports of the IP
address. And if the pool members for the virtual server are also listening on all ports (*),
it will send traffic to the servers on the port it arrived on the virtual server.
If you need to listen on multiple ports for the same IP address you can approach this in
two different ways. You can build a virtual server for each necessary port using the
same IP address or you can build one virtual server on all ports and use an iRule to
restrict the allowed inbound connections to your list of ports.
Where is the Virtual Server Listening?
When you configure a virtual server you tell the BIG-IP where you want it to listen for
traffic destined for the IP address of the virtual server. This virtual server setting is the
VLAN and Tunnel Traffic setting. By default the setting is set to All VLANs and Tunnels.
Which means the BIG-IP will listen on all VLANs. You are probably thinking, ARP is only
going to happen on the local subnet’s VLAN, which is true. So what can it possibly mean
to listen on all VLANs? When this setting is set to all VLANs it means that if traffic comes
to BIG-IP destined for the virtual server address from a VLAN that is not the VLAN of the
virtual server IP address, it will still take the traffic in on VLAN interface that it arrived
on. BIG-IP is a default deny device but in setting the setting to All VLANS and Tunnels
you have told the system to listen on all VLANs for traffic to the virtual server and allow
it in.
Link to Online Topic Content
Packet Filters
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Packet filters enhance network security by specifying whether a BIG-IP system interface
should accept or reject certain packets based on criteria that you specify. Packet filters
enforce an access policy on incoming traffic. They apply to incoming traffic only.
You implement packet filtering by creating packet filter rules, using the BIG-IP
Configuration utility. The primary purpose of a packet filter rule is to define the criteria
that you want the BIG-IP system to use when filtering packets. Examples of criteria that
you can specify in a packet filter rule are:



The source IP address of a packet
The destination IP address of a packet
The destination port of a packet
You specify the criteria for applying packet filter rules within an expression. When
creating a packet filter rule, you can instruct the BIG-IP system to build an expression for
you, in which case you need only choose the criteria from predefined lists, or you can
write your own expression text, using the syntax of the tcpdump utility. For more
information on the tcpdump utility, see the online man page for the tcpdump
command.
You can also configure global packet filtering that applies to all packet filter rules that
you create. The following sections describe how to use the Configuration utility to set
global packet filtering options, as well as create and manage individual packet filters
rules.
Link to Online Topic Content
iRules
You can use iRules to restrict traffic in almost anyway you can think of. You can set an
iRule to keep connections from happening when coming from a certain IP address range
or to a certain URI path in the HTTP request.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
1.02 - Explain how to use LTM as a service proxy
Since the F5 BIG-IP platform is designed as a full-proxy architecture the LTM can act as a
proxy for any service level connection.
You define the virtual server as a Standard virtual server that is listening on an IP
address and port combination, which represents the application to the client. The
virtual server should be configured with an appropriate layer-4 profile, any optional
layer-7 protocol profiles you need and a pool for a resource. The LTM will then broker
separate layer-4 connections for the client and server sides. The server side connections
will be translated from the listening IP address and port combination of the virtual
server to the IP address and port combination of the pool member that the connection
will be sent to via the load-balancing algorithm of the pool.
The return traffic must flow through the BIG-IP to be correctly rewritten as it passes
back to the client. The return traffic will be rewritten from the IP address and port
combination of the pool member that received the inbound connection to the IP
address and port combination of the virtual server that the client connected to when
the connection was established.
Link to Online Topic Content
Standard virtual server
The BIG-IP LTM TMOS operating system implements a full proxy architecture for virtual
servers configured with a TCP profile. By assigning a custom TCP profile to the virtual
server, you can configure the BIG-IP LTM system to maintain compatibility to disparate
server operating systems in the data center. At the same time, the BIG-IP LTM system
can leverage its TCP/IP stack on the client side of the connection to provide independent
and optimized TCP connections to client systems.
In a full proxy architecture, the BIG-IP LTM system appears as a TCP peer to both the
client and the server by associating two independent TCP connections with the end-toend session. Although certain client information, such as the source IP address or
source TCP port, may be re-used on the server side of the connection, the BIG-IP LTM
system manages the two sessions independently, making itself transparent to the client
and server.
The Standard virtual server requires a TCP or UDP profile, and may optionally be
configured with HTTP, FTP, or SSL profiles if Layer 7 or SSL processing is required.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
The TCP connection setup behavior for a Standard virtual server varies depending on
whether a TCP profile or a TCP and Layer 7 profile, such as HTTP, is associated with the
virtual server.
Standard virtual server with a TCP profile
The TCP connection setup behavior for a Standard virtual server operates as follows: the
three-way TCP handshake occurs on the client side of the connection before the BIG-IP
LTM system initiates the TCP handshake on the server side of the connection.
A Standard virtual server processes connections using the full proxy architecture. The
following TCP flow diagram illustrates the TCP handshake for a Standard virtual server
with a TCP profile:
Standard virtual server with Layer 7 functionality
If a Standard virtual server is configured with Layer 7 functionality, such as an HTTP
profile, the client must send at least one data packet before the server-side connection
can be initiated by the BIG-IP LTM system.
Note: The BIG-IP LTM system may initiate the server-side connection prior to the first
data packet for certain Layer 7 applications, such as FTP, in which case the user waits for
a greeting banner before sending any data.
The TCP connection setup behavior for a Standard virtual server with Layer 7
functionality operates as follows: the three-way TCP handshake and initial data packet
are processed on the client side of the connection before the BIG-IP LTM system
initiates the TCP handshake on the server side of the connection.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
A Standard virtual server with Layer 7 functionality processes connections using the full
proxy architecture. The following TCP flow diagram illustrates the TCP handshake for a
Standard virtual server with Layer 7 functionality:
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
1.02 - Describe how a given service is deployed on an LTM
Link to Online Topic Content
Processing HTTP traffic
The BIG-IP system allows you to process HTTP traffic using various profiles, including
TCP+HTTP, FastHTTP, and FastL4. Each profile, or combination of profiles, offers distinct
advantages, limitations, and features.
F5 recommends that you assess the needs of each HTTP virtual server individually, using
the following information, to determine which profile, or profile combination, best
meets the requirements for each virtual server.
Important: The HTTP profile will work in all cases; however, the HTTP profile places BIG-IP in
full Layer 7 inspection mode, which may be unnecessary when used on simple load
balancing virtual servers. Thus, you should consider the other profile options provided in
instances where the full Layer 7 engine is not necessary for a particular virtual server.
TCP+HTTP
Profiles: TCP+HTTP
Advantage: The HTTP profile can take full advantage of all of BIG-IP system's Layers 4 - 7
HTTP/HTTPS features.
When to use: The HTTP profile is used when any of the following features are required:











IPv6 support
TCPexpress and content spooling features reduce server load
Full OneConnect functionality (including HTTP 1.0 transformations)
Layer 7 persistence (cookie, hash, universal, and iRule)
Full HTTP iRules logic
Cache and Web Acceleration features
HTTP Compression
HTTP pipelining
Virtual Server Authentication
Redirect Rewriting
SPDY protocol support (11.3.0 and later)
Limitations


More CPU-intensive
Memory utilization:
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
◦
Cache / Web Acceleration
The caching / web acceleration features provision user-defined memory for
cache content for each virtual server that uses the given HTTP and Cache
profiles.
◦
Compression
Larger buffer sizes can increase memory utilization when compressing large
objects.
◦
TCP offloading/content spooling
This can increase memory utilization in cases where either the client-side or
the server-side of the connection is slower than the other. The BIG-IP system
holds the data in the buffer until the slower side of the connection is able to
retrieve it.
FastHTTP
Profile: FastHTTP
Advantage: Faster than HTTP profile
When to use: FastHTTP profile is recommended when it is not necessary to use
persistence and or maintain source IP addresses. FastHTTP also adds a subset of
OneConnect features to reduce the number of connections opened to the backend
HTTP servers. The FastHTTP profile requires that the clients' source addresses are
translated. If an explicit SNAT or SNAT pool is not specified, the appropriate self IP
address is used.
Note: Typically, server efficiency increases as the number of SNAT addresses that are
available to the virtual server increases. At the same time, the increase in SNAT addresses
that are available to the virtual server also decreases the likelihood that the virtual server
will reach the point of ephemeral port exhaustion (65535 open connections per SNAT
address).
Limitations



Requires client source address translation
Not compatible with persistence until version 10.0.0
Limited iRules support L4 and are limited to a subset of HTTP header operations,
and pool/pool member selection
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




No compression
No virtual server authentication
No support for HTTP pipelining
No TCP optimizations
No IPv6 support
Note: FastHTTP is optimized for ideal traffic conditions, but may not be an appropriate
profile to use when network conditions are less than optimal. For more information about
the FastHTTP profile, refer to SOL8024: Overview of the FastHTTP profile.
FastL4
Profile: FastL4
Advantage: Accelerates packet processing
When to use: FastL4 is limited in functionality to socket level decisions (for example,
src_ip:port dst_ip:port). Thus, you can use FastL4 only when socket level information
for each connection is required for the virtual server.
Limitations









No HTTP optimizations
No TCP optimizations for server offloading
SNAT/SNAT pools demote PVA acceleration setting level to Assisted
iRules limited to L4 events, such as CLIENT_ACCEPTED and SERVER_CONNECTED
No OneConnect
Limited persistence options:
◦ Source address
◦ Destination address
◦ Universal
◦ Hash (BIG-IP 9.x only)
No compression
No Virtual Server Authentication
No support for HTTP pipelining
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Objective - 1.03 - Given an application configuration, determine
which functions can be offloaded to the LTM device
1.03 - Explain how to offload HTTP servers for SSL, compression and
caching
Offloading
One of the most prominent advantages to having a BIG-IP platform in your network is
that it can offload functions from the server environment to improve their performance.
SSL termination, HTTP compression and RAM Caching are a few of the primary functions
Each of these optimizations are configurations that are completed in profiles assigned to
the virtual server.
Link to Online Topic Content
SSL Offload
The primary way to control SSL network traffic on the BIG-IP platform is by configuring a
Client or Server SSL profile:


A Client profile is a type of traffic profile that enables Local Traffic Manager to
accept and terminate any client requests that are sent by way of a fully SSLencapsulated protocol. Local Traffic Manager supports SSL for both TCP and UDP
protocols.
A Server profile is a type of profile that enables Local Traffic Manager to initiate
secure connections to a target web server.
To offloading of the overhead of processing SSL traffic from the server to the BIG-IP
platform you will need to follow these high level steps:
1. Install a key/certificate pair on the BIG-IP system for terminating client-side
secure connections.
2. Configure a client-side SSL profile using the new key/certificate pair.
3. Configure a virtual server to process the SSL traffic that uses the client-side SSL
profile and a pool of the servers defined on HTTP. This virtual server will listen
for HTTPS based traffic, terminate the SSL traffic and send the traffic to a pool
resource that is listening for HTTP based traffic.
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F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Link to Online Topic Content
HTTP compression
An optional feature of the BIG-IP system is the system’s ability to off-load HTTP
compression tasks from the target server. All of the tasks that you need to configure
HTTP compression, as well as the compression software itself, are centralized on the
BIG-IP system. The primary way to enable HTTP compression is by configuring an HTTP
Compression type of profile and then assigning the profile to a virtual server. This
causes the system to compress HTTP content for any responses matching the values
that you specify in the Request-URI or Content-Type settings of the HTTP Compression
profile.
When you configure an HTTP Compression profile and assign it to a virtual server, the
BIG-IP system reads the Accept-Encoding header of a client request and determines
what content encoding method the client prefers. The BIG-IP system then removes the
Accept-Encoding header from the request and passes the request to the server. Upon
receiving the server response, the BIG-IP system inserts the Content-Encoding header,
specifying either the gzip or deflate based on the compression method that the client
specifies in the Accept-Encoding header.
Configuration
You should be familiar with how the configuration of HTTP Compression looks in the CLI
Config as well as in the GUI.
To configure HTTP data compression, you need to create an HTTP compression type of
profile, as well as a virtual server.
Creating a customized HTTP compression profile
If you need to adjust the compression settings to optimize compression for your
environment, you can modify a custom HTTP compression profile.
1. On the Main tab, click Local Traffic > Profiles > Services > HTTP Compression.
The HTTP Compression profile list screen opens.
2. Click Create. The New HTTP Compression Profile screen opens.
3. In the Name field, type a name for the profile.
4. From the Parent Profile list, select one of the following profiles:
 httpcompression.
 wan-optimized-compression.
5. Select the Custom check box. The fields in the Settings area become available
for revision.
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6. Modify the settings, as required.
7. Click Finished.
The modified HTTP compression profile is available in the HTTP Compression list screen.
Creating a virtual server for HTTP compression
You can create a virtual server that uses an HTTP profile with an HTTP compression
profile to compress HTTP responses.
1. On the Main tab, click Local Traffic > Virtual Servers. The Virtual Server List
screen displays a list of existing virtual servers.
2. Click the Create button. The New Virtual Server screen opens.
3. In the Name field, type a unique name for the virtual server.
4. Specify the Destination setting, using the Address field; type the IP address you
want to use for the virtual server. The IP address you type must be available and
not in the loopback network.
5. In the Service Port field, type 80, or select HTTP from the list.
6. Select http in the HTTP Profile list.
7. From the HTTP Compression Profile list, select one of the following profiles:
 httpcompression
 wan-optimized-compression
 A customized profile
8. In the Resources area of the screen, from the Default Pool list, select a pool
name.
9. Click Finished.
The virtual server with an HTTP profile configured with an HTTP compression profile
appears in the Virtual Server list.
After you have created a custom HTTP Compression profile and a virtual server, you can
test the configuration by attempting to pass HTTP traffic through the virtual server.
Check to see that the BIG-IP system includes and excludes the responses that you
specified in the custom profile, and that the system compresses the data as specified.
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Link to Online Topic Content
Cacheing
To configure cacheing, you need to configure a Web Acceleration type of profile. These
settings provide the ability to turn on the cache and fine-tune it for a specific
implementation. Using a Web Acceleration type of profile, the system can store HTTP
objects stored in memory that are reused by subsequent connections to reduce the
amount of load on the back-end servers.
The default items stored by the cache are HTTP GET responses. However, you can
specify URIs in the URI list if you want to cache POST and GET methods for a particular
URI.
There are three types of Web Acceleration profiles that you can configure:



A basic Web Acceleration profile
An optimized acceleration profile
An optimized caching profile
When to use the cache feature
The cache feature provides the ability to reduce the traffic load to back-end servers.
This ability is useful if an object on a site is under high demand, if the site has a large
quantity of static content, or if the objects on the site are compressed.

High-demand objects
This feature is useful if a site has periods of high demand for specific content. With the
cache configured, the content server only has to serve the content to the BIG-IP system
once per expiration period.

Static content
This feature is also useful if a site consists of a large quantity of static content such as
CSS files, JavaScript files, or images and logos.

Content compression
For compressible data, the cache can store data for clients that can accept compressed
data. When used in conjunction with the compression feature on the BIG-IP system, the
cache takes stress off of the BIG-IP system and the content servers.
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Items you can cache
The cache feature is fully compliant with the cache specifications described in RFC 2616,
Hypertext Transfer Protocol -- HTTP/1.1. This means you can configure the cache
feature to cache the following content types:




200, 203, 206, 300, 301, and 410 responses
Responses to GET methods, by default
Other HTTP methods for URIs specified for inclusion in cached content, or
specified in an iRule
Content based on the User-Agent and Accept-Encoding values. The cache holds
different content for Vary headers.
The items that the cache does not cache are:


Private data specified by cache control headers
HEAD, PUT, DELETE, TRACE, and CONNECT methods, by default
The caching mechanism
The default cache configuration caches only responses to HTTP GET methods. However,
you can use the cache to cache other methods, too, including non-HTTP methods. You
do this by specifying a URI in the URI Include or Pin list within a Web Acceleration
profile, or by writing an iRule.
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Objective - 1.04 - Given an iRule functionality, determine the
profiles and configuration options necessary to implement the
iRule.
1.04 - Explain how to create an HTTP configuration to handle an HTTP
server error
Link to Online Topic Content
How to handle an HTTP server error
Configuring a virtual server on your BIG-IP platform to load balance the HTTP based
traffic for your webservers can be a very simple configuration. But you realize that
periodically a server returns an error and the clients are receiving a 404 error, and they
are leaving your site for a competitor’s site. You want to take an action on those errors
to send your customers to a “Sorry Page”.
If this were an issue of all of your servers be off line you could simply apply a custom
HTTP profile to the virtual server and set the Fallback Host field with the URL to your
Sorry Page. However this is happening intermittently on random server within the
pool.
You could apply an iRule to your virtual server to send your customer to your Sorry Page
when it sees the 404 error.
To do this, follow these steps:
1. Setup your Sorry Server to run the Sorry Page.
2. Write the iRule to meet your needs. The following is an example:
when HTTP_RESPONSE {
if { [HTTP::status] contains "404"} {
HTTP::redirect "http://www.mysorryserver.com/appsorrypage.html"
}
}
3. Apply an HTTP profile (the default http profile will work) to the virtual server so that the
virtual server will process the HTTP traffic allowing the iRule to work correctly.
4. Apply the new iRule to your virtual server.
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You could do further rule work to track info about the server when the errors happen
but it is not necessary to solve the problem.
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Objective - 1.05 - Given an application configuration, determine
the appropriate profile and persistence options
1.05 - Explain how to create an HTTP configuration for mobile clients
Link to Online Topic Content
Mobile Optimization
The BIG-IP system includes several pre-configured TCP profiles that you can use as is. In
addition to the default TCP profile, the system includes TCP profiles that are preconfigured to optimize LAN and WAN traffic, as well as traffic for mobile users. You can
use the pre-configured profiles as is, or you can create a custom profile based on a preconfigured profile and then adjust the values of the settings in the profiles to best suit
your particular network environment.
The tcp-cell-optimized profile is a pre-configured profile type, for which the default
values are set to give better performance to service providers' 3G and 4G customers.
Specific options in the pre-configured profile are set to optimize traffic for most mobile
users, and you can tune these settings to fit your network. For files that are smaller
than 1 MB, this profile is generally better than the mptcp-mobile-optimized profile. For
a more conservative profile, you can start with the tcp-mobile-optimized profile, and
adjust from there.
Note: Although the pre-configured settings produced the best results in the test lab,
network conditions are extremely variable. For the best results, start with the default
settings and then experiment to find out what works best in your network.
This list provides guidance for relevant settings



Set the Proxy Buffer Low to the Proxy Buffer High value minus 64 KB. If the
Proxy Buffer High is set to less than 64K, set this value at 32K.
The size of the Send Buffer ranges from 64K to 350K, depending on network
characteristics. If you enable the Rate Pace setting, the send buffer can handle
over 128K, because rate pacing eliminates some of the burstiness that would
otherwise exist. On a network with higher packet loss, smaller buffer sizes
perform better than larger. The number of loss recoveries indicates whether this
setting should be tuned higher or lower. Higher loss recoveries reduce the
goodput.
Setting the Keep Alive Interval depends on your fast dormancy goals. The
default setting of 1800 seconds allows the phone to enter low power mode while
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




keeping the flow alive on intermediary devices. To prevent the device from
entering an idle state, lower this value to under 30 seconds.
The Congestion Control setting includes delay-based and hybrid algorithms,
which might better address TCP performance issues better than fully loss-based
congestion control algorithms in mobile environments. The Illinois algorithm is
more aggressive, and can perform better in some situations, particularly when
object sizes are small. When objects are greater than 1 MB, goodput might
decrease with Illinois. In a high loss network, Illinois produces lower goodput
and higher retransmissions. The Woodside algorithm relies on timestamps to
determine transmission. If timestamps are not available in your network, avoid
using Woodside.
For 4G LTE networks, specify the Packet Loss Ignore Rate as 0. For 3G networks,
specify 2500. When the Packet Loss Ignore Rate is specified as more than 0, the
number of retransmitted bytes and receives SACKs might increase dramatically.
For the Packet Loss Ignore Burst setting, specify within the range of 6-12, if the
Packet Loss Ignore Rate is set to a value greater than 0. A higher Packet Loss
Ignore Burst value increases the chance of unnecessary retransmissions.
For the Initial Congestion Window Size setting, round trips can be reduced when
you increase the initial congestion window from 0 to 10 or 16.
Enabling the Rate Pace setting can result in improved goodput. It reduces loss
recovery across all congestion algorithms, except Illinois. The aggressive nature
of Illinois results in multiple loss recoveries, even with rate pacing enabled.
A tcp-mobile-optimized profile is similar to a TCP profile, except that the default values
of certain settings vary, in order to optimize the system for mobile traffic.
You can use the tcp-mobile-optimized profile as is, or you can create another custom
profile, specifying the tcp-mobile-optimized profile as the parent profile.
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1.05 - Explain how to create an HTTP configuration to optimize WAN
connectivity
Link to Online Topic Content
Optimize WAN Connectivity
You can use the tcp-wan-optimized profile to increase performance for environments
where a link has lower bandwidth and/or higher latency. You can also implement WAN
based Compression for HTTP traffic using the http compression profile.
The tcp-wan-optimized profile is a TCP-type profile. This profile is effectively a custom
profile that Local Traffic Manager has already created for you, derived from the default
tcp profile. This profile is useful for environments where a link has lower bandwidth
and/or higher latency when paired with a faster link.
In cases where the BIG-IP system is load balancing traffic over a WAN link, you can
enhance the performance of your wide-area TCP traffic by using the tcp-wan-optimized
profile.
If the traffic profile is strictly WAN-based, and a standard virtual server with a TCP
profile is required, you can configure your virtual server to use a tcp-wan-optimized
profile to enhance WAN-based traffic. For example, in many cases, the client connects
to the BIG-IP virtual server over a WAN link, which is generally slower than the
connection between the BIG-IP system and the pool member servers. By configuring
your virtual server to use the tcp-wan-optimized profile, the BIG-IP system can accept
the data more quickly, allowing resources on the pool member servers to remain
available. Also, use of this profile can increase the amount of data that the BIG-IP
system buffers while waiting for a remote client to accept that data. Finally, you can
increase network throughput by reducing the number of short TCP segments that the
BIG-IP system sends on the network.
A tcp-wan-optimized profile is similar to a TCP profile, except that the default values of
certain settings vary, in order to optimize the system for WAN-based traffic.
You can use the tcp-wan-optimized profile as is, or you can create another custom
profile, specifying the tcp-wan-optimized profile as the parent profile.
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1.05 - Determine when connection mirroring is required
Link to Online Topic Content
Connection Mirroring
The Connection Mirroring feature allows you to configure a BIG-IP system to duplicate
connection information to the standby unit of a redundant pair. This setting provides
higher reliability, but might affect system performance.
The BIG-IP systems are not stateful by default. In a BIG-IP redundant pair failover
scenario, the redundant unit of the pair does not know the active connection states. F5
BIG-IP gives the administrator the ability to enable connection mirroring on a virtual
server by virtual server basis.
Not all applications have to have their connection state know by the standby unit.
Mainly applications that have long-term connections will need to have their connections
mirrored.
For example, where long-term connections, such as FTP and Telnet, are good candidates
for mirroring, mirroring short-term connections, such as HTTP and UDP, is not
recommended as this causes a decrease in system performance. In addition, mirroring
HTTP and UDP connections is typically not necessary, as those protocols allow for failure
of individual requests without loss of the entire session.
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Objective - 1.06 - Explain the steps necessary to configure AVR
1.06 - Explain the steps necessary to configure the AVR
Link to Online Topic Content
Application Visibility and Reporting
Analytics (also called Application Visibility and Reporting (AVR)) is a module on the BIGIP system that you can use to analyze the performance of web applications. It provides
detailed metrics such as transactions per second, server and client latency, request and
response throughput, and sessions. You can view metrics for applications, virtual
servers, pool members, URLs, specific countries, and additional detailed statistics about
application traffic running through the BIG-IP system.
Transaction counters for response codes, user agents, HTTP methods, countries, and IP
addresses provide statistical analysis of the traffic that is going through the system. You
can capture traffic for examination and have the system send alerts so you can
troubleshoot problems and immediately react to sudden changes.
The Analytics module also provides remote logging capabilities so that your company
can consolidate statistics gathered from multiple BIG-IP appliances onto syslog servers
or SIEM devices, such as Splunk.
AVR Profile
An Analytics profile is a set of definitions that determines the circumstances under
which the system gathers, logs, notifies, and graphically displays information regarding
traffic to an application. The Analytics module requires that you select an Analytics
profile for each application you want to monitor. You associate the Analytics profile
with one or more virtual servers used by the application, or with an iApps application
service. Each virtual server can have only one Analytics profile associated with it.
In the Analytics profile, you customize:




What statistics to collect
Where to collect data (locally, remotely, or both)
Whether to capture the traffic itself
Whether to send notifications
The BIG-IP system includes a default Analytics profile called analytics. It is a minimal
profile that internally logs application statistics for server latency, throughput, response
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codes, and methods. You can modify the default profile, or create custom Analytics
profiles for each application if you want to track different data for each one.
Charts shown on the Statistics > Analytics screens display the application data saved for
all Analytics profiles associated with iApps application services or virtual servers on the
system. You can filter the information, for example, by application or URL. You can also
drill down into the specifics on the charts, and use the options to further refine the
information in the charts.
Setting Up AVR
You can collect application statistics for one or more virtual servers or for an iApps
application service. If virtual servers are already configured, you can specify them when
setting up statistics collection. If you want to collect statistics for an iApps application
service, you should first set up statistics collection, creating an Analytics profile, and
then create the application service.
You need to provision the AVR module before you can set up local application statistics
collection. You must have Adobe® Flash® Player installed on the computer where you
plan to view Analytics statistics.
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1.06 - Explain how to create an AVR profile and options
Link to Online Topic Content
AVR profile and options
Setting up local application statistics collection
You need to provision the AVR module before you can set up local application statistics
collection. You must have Adobe® Flash® Player installed on the computer where you
plan to view Analytics statistics.
You can configure the BIG-IP system to collect specific application statistics locally.
1. On the Main tab, click Local Traffic > Profiles > Analytics.
Tip: If Analytics is not listed, this indicates that Application Visibility and Reporting (AVR)
is not provisioned, or you do not have rights to create profiles.
The Analytics screen opens and lists all Analytics profiles that are on the system,
including a default profile called analytics.
2. Click Create.
The New Analytics Profile screen opens. By default, the settings are initially the same as
in the default analytics profile.
3. In the Profile Name field, type a name for the Analytics profile.
4. For the Statistics Logging Type setting, verify that Internal is selected. If it is not, select
the check box on the right first to activate the setting, then select Internal.
Selecting Internal causes the system to store statistics locally, and you can view the
charts on the system by clicking Overview > Statistics > Analytics.
5. Review the read-only Transaction Sampling Ratio value, which shows the current global
(analytics) status of sampling for the system.
Learning from all transactions provides the most accurate statistical data but impacts
performance. The system can perform traffic sampling; for example, sampling 1 of
every 99 transactions; sampling is less precise but demands fewer resources. If you
need to change the value, you can do it later by editing the default analytics profile.
If using traffic sampling, the Traffic Capturing Logging Type setting and User Sessions
metric option are not available.
6. In the Included Objects area, specify the virtual servers for which to capture application
statistics:
a. For the Virtual Servers setting, click Add.
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A popup lists the virtual servers that you can assign to the Analytics profile.
b. From the Select Virtual Server popup list, select the virtual servers to include
and click Done.
Note: You need to have previously configured the virtual servers (with an HTTP
profile) for them to appear in the list. Also, you can assign only one Analytics
profile to a virtual server so the list shows only virtual servers that have not
been assigned an Analytics profile.
Special considerations apply if using Analytics on a BIG-IP system with both Application
Security Manager and Access Policy Manager, where security settings (in Portal Access
webtop or an iRule) redirect traffic from one virtual server to a second one. In this case,
you need to attach the Analytics profile to the second virtual server to ensure that the
charts show accurate statistics.
7. To the right of the Statistics Gathering Configuration area, select the Custom check box.
The settings in the area become available for modification.
8. In the Statistics Gathering Configuration, for Collected Metrics, select the statistics you
want the system to collect:
Option
Description
Server
Latency
Page Load
Time
Tracks how long it takes to get data from the application server to
the BIG-IP system (selected by default).
Tracks how long it takes an application user to get a complete
response from the application, including network latency and
completed page processing.
Note: End user response times and latencies can vary
significantly based on geography and connection types.
Saves information about HTTP request and response throughput
(selected by default).
Stores the number of unique user sessions. For Timeout, type the
number of minutes of user non-activity to allow before the system
considers the session to be over. If using transaction sampling,
this option is not available.
Throughput
User
Sessions
9. For Collected Entities, select the entities for which you want the system to collect
statistics:
Option
Description
URLs
Countries
Collects the requested URLs.
Saves the name of the country where the
request came from based on the client IP
address.
Saves the IP address where the request
originated. The address saved also
depends on whether the request has an
XFF (X-forwarded-for) header and whether
Client IP Addresses
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Response Codes
User Agents
Methods
Trust XFF is selected.
Saves HTTP response codes that the
server returned to requesters (selected by
default).
Saves information about browsers used
when making the request.
Saves HTTP methods in requests
(selected by default).
10. Click Finished.
11. If you need to adjust the Transaction Sampling Ratio value, click the default analytics
profile on the Profiles: Analytics screen.
You can use the sampling ratio to fine-tune the tradeoff between more accurate data
and a possible performance impact. The value set here applies to all Analytics profiles
on the system.


Select all to collect all of the traffic that is being monitored and produce the
most accurate results; it also poses the risk of performance reduction.
Select 1 of every n to sample every nth transaction; not all possible traffic is
processed producing more generalized results, but performance is better.
Generally, it is best to use all when the BIG-IP system has low TPS, and use 1 of every n
when it has high TPS (for example, select 1 of every 20 to sample every twentieth
request).
If you enable sampling (by selecting a setting other than all), the User Sessions metric
and Traffic Capturing Logging Type settings become unavailable.
The BIG-IP system collects statistics about the application traffic described by the
Analytics profile. You can view the statistics by clicking Statistics > Analytics.
If you want to monitor statistics for an iApps application, create the iApp application
service, enable Analytics on the template, and specify the Analytics profile you just
created. The BIG-IP system then collects statistics for the application service, and the
application name appears in the Analytics charts.
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Objective - 1.07 - Given a set of reporting requirements,
determine the AVR metrics and entities to collect
1.07 - Given a set of reporting requirements, determine the AVR metrics
and entities to collect
AVR Metrics and Entities to Collect
As you are working with AVR in your vLab and looking at results of the metrics that you
gather, you should be paying attention to what AVR allows you to collect like Server
Latency, Page Load Time, Throughput and User Sessions. You should also know what
each of these mean (defined in the last section). You should also be aware of what you
can gather that information for, such as URLs, Countries, Client IP Addresses, Response
Codes, User Agents and Methods. You should also know what each of those mean
(defined in the last section).
1.07 - Explain the sizing implications of AVR on the LTM device
Link to Online Topic Content
AVR Sizing
Provisioning AVR can be as impactful as provisioning any other licensed module. AVR
requires CPU and Memory resources to function. As you increase the use of AVR within
the BIG-IP device it can continue to further impact system resources. If you intend to
use AVR on your BIG-IP environment you should consider the resource impact when you
are doing platform sizing, as if it were any other heavy impact licensable software for
the system.
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1.07 - Explain the logging and notifications options of AVR
Link to Online Topic Content
AVR
You can examine the statistics in the Analytics charts when Application Visibility and
Reporting (AVR) is provisioned. Analytics charts display statistical information about
traffic on your system, including the following details:





Overview
Transactions
Latency
Throughput
Sessions
The system updates the Analytics statistics every five minutes (you can refresh the
charts periodically to see the updates). The Analytics Overview provides a summary of
the most frequent recent types of application traffic, such as the top virtual servers, top
URLS, top pool members, and so on. You can customize the Analytics Overview so that
it shows the specific type of data you are interested in. You can also export the reports
to a PDF or CSV file, or send the reports to one or more email addresses.
Note: The displayed Analytics statistics are rounded up to two digits, and might be slightly
inaccurate.
Before you can look at the application statistics, you need to have created an Analytics
profile so that the system is capturing the application statistics internally on the BIG-IP
system. You must associate the Analytics profile with one or more virtual servers (in the
Analytics profile or in the virtual server). If you created an iApp application service, you
can use the provided template to associate the virtual server. To view Analytics
statistics properly, you must have Adobe Flash Player installed on the computer where
you plan to view them.
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1.07 - Explain the uses of the collected metrics and entities
Link to Online Topic Content
Uses of AVR
You can review charts that show statistical information about traffic to your web
applications. The charts provide visibility into application behavior, user experience,
transactions, and data center resource usage.
Collected Metrics
OPTION
DESCRIPTION
Server
Latency
Page Load
Time
Tracks how long it takes to get data from the application server to the
BIG-IP system (selected by default).
Tracks how long it takes an application user to get a complete response
from the application, including network latency and completed page
processing.
Note: End user response times and latencies can vary significantly based
on geography and connection types.
Saves information about HTTP request and response throughput
(selected by default).
Stores the number of unique user sessions. For Timeout, type the
number of minutes of user non-activity to allow before the system
considers the session to be over. If using transaction sampling, this
option is not available.
Throughput
User
Sessions
Collected Entities
OPTION
DESCRIPTION
URLs
Countries
Collects the requested URLs.
Saves the name of the country where the request came from based on
the client IP address.
Saves the IP address where the request originated. The address saved
also depends on whether the request has an XFF (X-forwarded-for)
header and whether Trust XFF is selected.
Saves HTTP response codes that the server returned to requesters
(selected by default).
Saves information about browsers used when making the request.
Saves HTTP methods in requests (selected by default).
Client IP
Addresses
Response
Codes
User Agents
Methods
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Objective - 1.08 - Given a scenario, determine the appropriate
monitor type and parameters to use
1.08 - Explain how to create an application specific monitor
Link to Online Topic Content
Application Specific Monitor
You can set up the BIG-IP system to monitor the health or performance of certain nodes
or servers that are members of a load balancing pool. Monitors verify connections on
pool members and nodes. A monitor can be either a health monitor or a performance
monitor, designed to check the status of a pool, pool member, or node on an ongoing
basis, at a set interval. If a pool member or node being checked does not respond
within a specified timeout period, or the status of a pool member or node indicates that
performance is degraded, the BIG-IP system can redirect the traffic to another pool
member or node.
Some monitors are included as part of the BIG-IP system, while other monitors are usercreated. Monitors that the BIG-IP system provides are called pre-configured monitors.
User-created monitors are called custom monitors.
Before configuring and using monitors, it is helpful to understand some basic concepts
regarding monitor types, monitor settings, and monitor implementation.
Monitor types
Every monitor, whether pre-configured or custom, is a certain type of monitor. Each
type of monitor checks the status of a particular protocol, service, or application. For
example, one type of monitor is HTTP. An HTTP type of monitor allows you to monitor
the availability of the HTTP service on a pool, pool member, or node. A WMI type of
monitor allows you to monitor the performance of a pool, pool member, or node that is
running the Windows Management Instrumentation (WMI) software. An ICMP type of
monitor simply determines whether the status of a node is up or down.
Link to Online Topic Content
About application check monitors
An application check monitor interacts with servers by sending multiple commands and
processing multiple responses.
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An FTP monitor, for example, connects to a server, logs in by using a user ID and
password, navigates to a specific directory, and then downloads a specific file to the
/var/tmp directory. If the file is retrieved, the check is successful.
1. Local Traffic Manager opens a TCP connection to an IP address and port, and logs
in to the server.
2. A specified directory is located and a specific file is requested.
3. The server sends the file to Local Traffic Manager.
4. Local Traffic Manager receives the file and closes the TCP connection.
About content check monitors
A content check monitor determines whether a service is available and whether the
server is serving the appropriate content. This type of monitor opens a connection to an
IP address and port, and then issues a command to the server. The response is
compared to the monitor's receive rule. When a portion of the server's response
matches the receive rule, the test is successful.
1. Local Traffic Manager opens a TCP connection to an IP address and port, and
issues a command to the server.
2. The server sends a response.
3. Local Traffic Manager compares the response to the monitor's receive rule and
closes the connection
Creating a custom HTTP monitor
Before creating a monitor, you must decide on a monitor type.
A custom HTTP monitor enables you to send a command to a server and examine that
server's response, thus ensuring that it is serving appropriate content.
Note: An HTTP monitor can monitor Outlook® Web Access (OWA) in Microsoft® Exchange
Server 2007 and Microsoft® SharePoint® 2007 web sites that require NT LAN Manager
(NTLM) authentication. NTLM authentication requires a send string that complies with
HTTP/1.1, a user name, and a password.
1. On the Main tab, click Local Traffic > Monitors. The Monitor List screen opens.
2. Type a name for the monitor in the Name field.
3. From the Type list, select HTTP.
The screen refreshes, and displays the configuration options for the HTTP
monitor type.
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4. From the Import Settings list, select http.
The new monitor inherits initial configuration values from the existing monitor.
5. In the Configuration area of the screen, select Advanced.
This selection makes it possible for you to modify additional default settings.
6. Type a number in the Interval field that indicates, in seconds, how frequently the
system issues the monitor check. The default is 5 seconds.
7. From the Up Interval list, do one of the following:


Accept the default, Disabled, if you do not want to use the up interval.
Select Enabled, and specify how often you want the system to verify the health of a
resource that is up.
8. Type a number in the Time Until Up field that indicates the number of seconds to
wait after a resource first responds correctly to the monitor before setting the
resource to up.
The default value is 0 (zero), which disables this option.
9. Type a number in the Timeout field that indicates, in seconds, how much time
the target has to respond to the monitor check. The default is 30 seconds.
If the target responds within the allotted time period, it is considered up. If the
target does not respond within the time period, it is considered down.
10. Specify whether the system automatically enables the monitored resource,
when the monitor check is successful, for Manual Resume.
This setting applies only when the monitored resource has failed to respond to a
monitor check.
Option Description
Yes
No
The system does nothing when the monitor check succeeds, and you
must manually enable the monitored resource.
The system automatically re-enables the monitored resource after the
next successful monitor check.
11. Type a text string in the Send String field that the monitor sends to the target
resource. The default string is GET /\r\n. This string retrieves a default file from
the web site.
Important: Send string syntax depends upon the HTTP version. Please observe
the following conventions.
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Version
Convention
HTTP 0.9
HTTP 1.0
HTTP 1.1
"GET /\n" or "GET /\r\n".
"GET / HTTP/1.0\r\n\r\n" or "GET /HTTP/1.0\n\n"
"GET / HTTP/1.1\r\nHost: server.com\r\n\r\n" or "GET
/HTTP/1.1\r\nHost: server.com\r\nConnection: close\r\n\r\n"
Type a fully qualified path name, for example, "GET
/www/example/index.html\r\n", if you want to retrieve a specific web site page.
12. Type a regular expression in the Receive String field that represents the text
string that the monitor looks for in the returned resource.
The most common receive expressions contain a text string that is included in an
HTML file on your site. The text string can be regular text, HTML tags, or image
names.
Note: If you do not specify both a send string and a receive string, the monitor performs
a simple service check and connect only.
13. Type a regular expression in the Receive Disable String field that represents the
text string that the monitor looks for in the returned resource.
Use a Receive String value together with a Receive Disable String value to match
the value of a response from the origin web server and create one of three
states for a pool member or node: Up (Enabled), when only Receive String
matches the response; Up (Disabled), when only Receive Disable String matches
the response; or Down, when neither Receive String nor Receive Disable String
matches the response.
Note: If you choose to set the Reverse setting to Yes, the Receive Disable String option
becomes unavailable and the monitor marks the pool, pool member, or node Down
when the test is successful.
14. Type a name in the User Name field.
15. Type a password in the Password field.
16. For the Reverse setting, do one of the following:


Accept the No default option.
Select the Yes option to make the Receive Disable String option unavailable and
mark the pool, pool member, or node Down when the test is successful.
17. For the Transparent setting, do one of the following:


Accept the No default option.
Select the Yes option to use a path through the associated pool members or nodes
to monitor the aliased destination.
The HTTP monitor is configured to monitor HTTP traffic.
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1.08 - Given a desired outcome, determine where to apply health
monitors
Link to Online Topic Content
Applying Health Monitors
You must associate a monitor with the server or servers to be monitored. The server or
servers can either be a pool, a pool member, or a node, depending on the monitor type.
Association types
You can associate a monitor with a server in any of these ways:
Monitor-to-pool association
This type of association associates a monitor with an entire load balancing pool. In this
case, the monitor checks all members of the pool. For example, you can create an
instance of the monitor http for every member of the pool my_pool, thus ensuring that
all members of that pool are checked.
Monitor-to-pool member association
This type of association associates a monitor with an individual pool member, that is, an
IP address and service. In this case, the monitor checks only that pool member and not
any other members of the pool. For example, you can create an instance of the monitor
http for pool member 10.10.10.10:80 of my_pool.
Monitor-to-node association
This type of association associates a monitor with a specific node. In this case, the
monitor checks only the node itself, and not any services running on that node. For
example, you can create an instance of the monitor ICMP for node 10.10.10.10. In this
case, the monitor checks the specific node only, and not any services running on that
node.
You can designate a monitor as the default monitor that you want Local Traffic Manager
to associate with one or more nodes. In this case, any node to which you have not
specifically assigned a monitor inherits the default monitor.
Some monitor types are designed for association with nodes only, and not pools or pool
members. Other monitor types are intended for association with pools and pool
members only, and not nodes.
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Node-only monitors specify a destination address in the format of an IP address with no
service port (for example, 10.10.10.2). Conversely, monitors that you can associate with
nodes, pools, and pool members specify a destination address in the format of an IP
address and service port (for example, 10.10.10.2:80). Therefore, when you use the
Configuration utility to associate a monitor with a pool, pool member, or node, the
utility displays only those pre-configured monitors that are designed for association with
that server.
For example, you cannot associate the monitor ICMP with a pool or its members, since
the ICMP monitor is designed to check the status of a node itself and not any service
running on that node.
Monitor instances
When you associate a monitor with a server, Local Traffic Manager automatically
creates an instance of that monitor for that server. A monitor association thus creates
an instance of a monitor for each server that you specify. This means that you can have
multiple instances of the same monitor running on your servers.
Because instances of monitors are not partitioned objects, a user can enable or disable
an instance of a monitor without having permission to manage the associated pool or
pool member.
For example, a user with the Manager role, who can access partition AppA only, can
enable or disable monitor instances for a pool that resides in partition Common.
However, that user cannot perform operations on the pool or pool members that are
associated with the monitor. Although this is correct functionality, the user might not
expect this behavior. You can prevent this unexpected behavior by ensuring that all
pools and pool members associated with monitor instances reside in the same partition.
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1.08 - Determine under which circumstances an external monitor is
required
REF 1 p 19-6
External Monitor
An external monitor allows you to monitor services using your own programs. Your
program tests services in any way you wish; the monitor need only know the name of
the program. Once the BIG-IP system initiates the external program, it waits for any
response set to standard out. If a response is seen the monitor is considered a success.
If no response to scene prior to the timeout being reached the mantra has failed.
If the template health monitors that the BIG-IP platform executes directly will not work
to monitor your application you can use an external monitor and call a script to check
your application.
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Objective - 1.09 - Given a set of parameters, predict an outcome
of a monitor status on other LTM device objects
1.09 - Determine the effect of a monitor on the virtual server status
Link to Online Topic Content
Effect of Monitoring
Health monitoring with a BIG-IP allows you to monitor resources at many different
levels. Monitors are assigned to resources in two areas of the configuration, at the node
level and at the pool level. At the node level you can assign monitors to all nodes
(Default Monitor) or to each node (Node Specific). At the pool level you can assign
monitors to all pool members (Default Pool Monitor) or to each member (Member
Specific).
If a monitor at the node level marks the node down, then pool member that uses the
node IP address as its member IP address will automatically be marked down. This
function works as a parent-child relationship between the node and the pool member.
These monitors are typically network level monitors (ping, TCP half open)
When a pool member that is being monitored by a health monitor does not respond to
a probe from the BIG-IP system within a specified timeout period, the system marks the
pool member down and no longer load balances traffic to that pool member. If all of
the pool members are marked off line and no pool members are available to service the
request then the pool is marked down and thus the virtual server is marked down. The
status of a virtual server works as a parent-child relationship between the pool and the
virtual server.
When the failing health monitor starts to succeed again and at least one pool member is
able to respond, then pool will be marked available and thus the virtual server will also
become available.
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1.09 - Determine the effect of active versus inline monitors on the
application status or on the LTM device
Link to Online Topic Content
Active Monitoring
Active monitoring checks the status of a pool member or node on an ongoing basis as
specified. If a pool member or node does not respond within a specified timeout
period, or the status of a node indicates that performance is degraded, the BIG-IP
system can redirect the traffic to another pool member or node. There are many active
monitors. Each active monitor checks the status of a particular protocol, service, or
application. For example, one active monitor is HTTP. An HTTP monitor allows you to
monitor the availability of the HTTP service on a pool, pool member, or node. A WMI
monitor allows you to monitor the performance of a node that is running the Windows
Management Instrumentation (WMI) software. Active monitors fall into two categories:
Extended Content Verification (ECV) monitors for content checks, and Extended
Application Verification (EAV) monitors for service checks, path checks, and application
checks.
An active monitor can check for specific responses, and run with or without client traffic.
Note: An active monitor also creates additional network traffic beyond the client request
and server response and can be slow to mark a pool member as down.
Passive monitoring
Passive monitoring occurs as part of a client request. This kind of monitoring checks the
health of a pool member based on a specified number of connection attempts or data
request attempts that occur within a specified time period. If, after the specified
number of attempts within the defined interval, the system cannot connect to the
server or receive a response, or if the system receives a bad response, the system marks
the pool member as down. There is only one passive monitor, called an Inband monitor.
A passive monitor creates no additional network traffic beyond the client request and
server response. It can mark a pool member as down quickly, as long as there is some
amount of network traffic.
Note: A passive monitor cannot check for specific responses and can potentially be slow to
mark a pool member as up.
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Objective - 1.10 - Given a set of SSL requirements, determine the
appropriate profile options to create or modify in the SSL profile
1.10 - Describe the difference between client and server SSL profiles
Link to Online Topic Content
Differences between Client and Server SSL Profiles
With LTM, you can enable SSL traffic management for either client-side traffic or serverside traffic.
Client-side traffic refers to connections between a client system and the BIG-IP system.
Server-side traffic refers to connections between the BIG-IP system and a target server
system:
Client-side SSL traffic
When you enable the BIG-IP system to manage client-side SSL traffic, LTM terminates
incoming SSL connections by decrypting the client request. LTM then sends the request,
in clear text, to a target server. Next, LTM retrieves a clear-text response (such as a web
page) and encrypts the request, before sending the web page back to the client. During
the process of terminating an SSL connection, LTM can, as an option, perform all of the
SSL certificate verification functions normally handled by the target web server.
Server-side SSL traffic
When you enable LTM to manage server-side SSL traffic, LTM enhances the security of
your network by re-encrypting a decrypted request before sending it on to a target
server. In addition to this re-encryption, LTM can, as an option, perform the same
verification functions for server certificates that LTM can for client certificates.
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1.10 - Describe the difference between client and server SSL processing
Link to Online Topic Content
Differences
A Client profile is a type of traffic profile that enables Local Traffic Manager to accept
and terminate any client requests that are sent by way of a fully SSL-encapsulated
protocol. Local Traffic Manager supports SSL for both TCP and UDP protocols.
A Server profile is a type of profile that enables Local Traffic Manager to initiate secure
connections to a target web server.
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Objective - 1.11 - Given a set of application requirements,
describe the steps necessary to configure SSL
1.11 - Describe the process to update expired SSL certificates
Link to Online Topic Content
Update Expired SSL Certs
Some Certificate Authorities allow you to renew a certificate by requesting a new
certificate using the Certificate Signing Request (CSR) on file, or by generating a new
CSR. However, you may choose to generate a new private SSL key and then generate a
new CSR from that new private SSL key.
Note: To prevent any disruption to traffic or services, F5 recommends that you renew a
certificate before the existing certificate expires.
Generating a new SSL key
To generate a new SSL key and prevent the existing SSL key and certificate from being
overwritten, perform the following procedure:
1.
2.
3.
4.
5.
6.
Log in to the BIG-IP LTM Configuration utility.
Select Local Traffic.
Select SSL Certificates.
Select Create.
Select Certificate Authority from the Issuer drop-down menu.
Enter a name for the SSL key file, and append a number or date at the end of the
name.
Note: By naming the file in this format, you can have the same file name as the previous
file and the system treats it as a separate file.
For example, you can change www.mysite.local to use the syntax of one of the following
SSL key name examples:
www.mysite.local2
www.mysite.localMMDDYYYY
7. Enter the Certificate properties information as they are listed in the previous SSL
key.
Note: To view the information that is listed in the existing SSL key, select the name and
certificate from the SSL Certificates List.
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8. The new SSL key information should appear similar to the following example:
Name: www.mysite.local2
Common Name: www.mysite.local
Organization: F5 Networks
Division: AskF5
Locality: Seattle
State Or Province: WA
Country: US
9. Click Finished.
10. Send the generated CSR to the CA to obtain a new certificate.
11. Import the new certificate by selecting Import.
12. Select Certificate from the drop-down menu.
13. Enter a name for the certificate using the same name you gave to the SSL key
created in step 6.
Note: Using the same name for both the key and certificate does not cause any
problems as the two files are saved with different extensions.
14. Select Upload File or Paste Text.
15. Click Finished.
Updating the SSL profile with the new SSL key and certificate
Note: Once the new key and certificate are installed on the BIG-IP LTM system, F5
recommends that you update the new key and certificate during a maintenance window to
prevent any disruption to SSL traffic.
To update the SSL profile, perform the following procedure:
1.
2.
3.
4.
5.
6.
7.
8.
Log in to the BIG-IP LTM Configuration utility.
Select Local Traffic.
Select Profiles.
Select SSL.
Choose Client or Server.
Select the profile for which you are going to switch the SSL key and certificate.
Select the new SSL key and certificate from the appropriate drop-down menu.
Click Finished.
Note: Existing connections will continue to use the old SSL certificate until the
connections complete, are renegotiated, or TMM is restarted.
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1.11 - Describe the steps to incorporate client authentication to the SSL
process
Link to Online Topic Content
Client Authentication
In a TLS handshake, the client and the server exchange several messages that ultimately
result in an encrypted channel for secure communication. During this handshake, the
client authenticates the server's identity by verifying the server certificate (for more on
the TLS handshake, see article 1 of this series). Although the client always authenticates
the server's identity, the server is not required to authenticate the client's identity.
However, there are some situations that call for the server to authenticate the client.
Client authentication is a feature that lets you authenticate users that are accessing a
server. In client authentication, a certificate is passed from the client to the server and
is verified by the server. Client authentication allow you to rest assured that the person
represented by the certificate is the person you expect. Many companies want to
ensure that only authorized users can gain access to the services and content they
provide. As more personal and access-controlled information moves online, client
authentication becomes more of a reality and a necessity.
How Does Client Authentication Work?
Before we jump into client authentication, let's make sure we understand server
authentication. During the TLS handshake, the client authenticates the identity of the
server by verifying the server's certificate and using the server's public key to encrypt
data that will be used to compute the shared symmetric key. The server can only
generate the symmetric key used in the TLS session if it can decrypt that data with its
private key. The following diagram shows an abbreviated version of the TLS handshake
that highlights some of these concepts.
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Ultimately, the client and server need to use a symmetric key to encrypt all
communication during their TLS session. In order to calculate that key, the server
shares its certificate with the client (the certificate includes the server's public key), and
the client sends a random string of data to the server (encrypted with the server's public
key). Now that the client and server each have the random string of data, they can each
calculate (independently) the symmetric key that will be used to encrypt all remaining
communication for the duration of that specific TLS session. In fact, the client and
server both send a "Finished' message at the end of the handshake...and that message is
encrypted with the symmetric key that they have both calculated on their own. So, if all
that stuff works and they can both read each other's "Finished" message, then the
server has been authenticated by the client and they proceed along with smiles on their
collective faces (encrypted smiles, of course).
You'll notice in the diagram above that the server sent its certificate to the client, but
the client never sent its certificate to the server. When client authentication is used, the
server still sends its certificate to the client, but it also sends a "Certificate Request"
message to the client. This lets the client know that it needs to get its certificate ready
because the next message from the client to the server (during the handshake) will need
to include the client certificate. The following diagram shows the added steps needed
during the TLS handshake for client authentication.
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So, you can see that when client authentication is enabled, the public and private keys
are still used to encrypt and decrypt critical information that leads to the shared
symmetric key. In addition to the public and private keys being used for authentication,
the client and server both send certificates and each verifies the certificate of the other.
This certificate verification is also part of the authentication process for both the client
and the server. The certificate verification process includes four important checks. If
any of these checks do not return a valid response, the certificate verification fails
(which makes the TLS handshake fail) and the session will terminate.
These checks are as follows:
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1.
2.
3.
4.
Check digital signature
Check certificate chain
Check expiration date and validity period
Check certificate revocation status
Here's how the client and server accomplish each of the checks for client authentication:
1. Digital Signature: The client sends a "Certificate Verify" message that contains a
digitally signed copy of the previous handshake message. This message is signed
using the client certificate's private key. The server can validate the message
digest of the digital signature by using the client's public key (which is found in
the client certificate). Once the digital signature is validated, the server knows
that public key belonging to the client matches the private key used to create the
signature.
2. Certificate Chain: The server maintains a list of trusted CAs, and this list
determines which certificates the server will accept. The server will use the
public key from the CA certificate (which it has in its list of trusted CAs) to
validate the CA's digital signature on the certificate being presented. If the
message digest has changed or if the public key doesn't correspond to the CA's
private key used to sign the certificate, the verification fails and the handshake
terminates.
3. Expiration Date and Validity Period: The server compares the current date to the
validity period listed in the certificate. If the expiration date has not passed and
the current date is within the period, everything is good. If it's not, then the
verification fails and the handshake terminates.
4. Certificate Revocation Status: The server compares the client certificate to the
list of revoked certificates on the system. If the client certificate is on the list,
the verification fails and the handshake terminates.
As you can see, a bunch of stuff has to happen in just the right way for the ClientAuthenticated TLS handshake to finalize correctly. If any piece is not setup correctly the
communication flow will fail. Something as simple as not including a necessary Chain
Certificate will cause the clients browser to pop a warning for trust issues, even if you
are using the correct certificates. But, all this is in place for your own protection. After
all, you want to make sure that no one else can steal your identity and impersonate you
on a critically important website!
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BIG-IP Configuration
Now that we've established the foundation for client authentication in a TLS handshake,
let's figure out how the BIG-IP is set up to handle this feature. The following screenshot
shows the user interface for configuring Client Authentication.
To get here, navigate to Local Traffic > Profiles > SSL > Client.
The Client Certificate drop down menu has three settings: Ignore (default), Require, and
Request. The "Ignore" setting specifies that the system will ignore any certificate
presented and will not authenticate the client before establishing the SSL session. This
effectively turns off client authentication. The "Require" setting enforces client
authentication. When this setting is enabled, the BIG-IP will request a client certificate
and attempt to verify it. An SSL session is established only if a valid client certificate
from a trusted CA is presented. Finally, the "Request" setting enables optional client
authentication. When this setting is enabled, the BIG-IP will request a client certificate
and attempt to verify it. However, an SSL session will be established regardless of
whether or not a valid client certificate from a trusted CA is presented. The Request
option is often used in conjunction with iRules in order to provide selective access
depending on the certificate that is presented. For example: let's say you would like to
allow clients who present a certificate from a trusted CA to gain access to the
application while clients who do not provide the required certificate be redirected to a
page detailing the access requirements. If you are not using iRules to enforce a different
outcome based on the certificate details, there is no significant benefit to using the
"Request" setting versus the default "Ignore" setting. In both cases, an SSL session will
be established regardless of the certificate presented.
Frequency specifies the frequency of client authentication for an SSL session. This menu
offers two options: Once (default) and Always. The "Once" setting specifies that the
system will authenticate the client only once for an SSL session. The "Always" setting
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specifies that the system will authenticate the client once when the SSL session is
established as well as each time that session is reused.
The Retain Certificate box is checked by default. When checked, the client certificate is
retained for the SSL session.
Certificate Chain Traversal Depth specifies the maximum number of certificates that can
be traversed in a client certificate chain. The default for this setting is 9. Remember
that "Certificate Chain" part of the verification checks? This setting is where you
configure the depth that you allow the server to dig for a trusted CA. For more on
certificate chains, see article 2 of this SSL series.
Trusted Certificate Authorities setting is used to specify the BIG-IP's Trusted Certificate
Authorities store. These are the CAs that the BIG-IP trusts when it verifies a client
certificate that is presented during client authentication. The default value for the
Trusted Certificate Authorities setting is None, indicating that no CAs are trusted. Don't
forget...if the BIG-IP Client Certificate menu is set to Require but the Trusted Certificate
Authorities is set to None, clients will not be able to establish SSL sessions with the
virtual server. The drop down list in this setting includes the name of all the SSL
certificates installed in the BIG-IP's /config/ssl/ssl.crt directory. A newly-installed BIG-IP
system will include the following certificates: default certificate and ca-bundle
certificate. The default certificate is a self-signed server certificate used when testing
SSL profiles. This certificate is not appropriate for use as a Trusted Certificate
Authorities certificate bundle. The ca-bundle certificate is a bundle of CA certificates
from most of the well-known PKIs around the world. This certificate may be appropriate
for use as a Trusted Certificate Authorities certificate bundle. However, if this bundle is
specified as the Trusted Certificate Authorities certificate store, any valid client
certificate that is signed by one of the popular Root CAs included in the default cabundle.crt will be authenticated. This provides some level of identification, but it
provides very little access control since almost any valid client certificate could be
authenticated.
If you want to trust only certificates signed by a specific CA or set of CAs, you should
create and install a bundle containing the certificates of the CAs whose certificates you
trust. The bundle must also include the entire chain of CA certificates necessary to
establish a chain of trust. Once you create this new certificate bundle, you can select it
in the Trusted Certificate Authorities drop down menu.
The Advertised Certificate Authorities setting is used to specify the CAs that the BIG-IP
advertises as trusted when soliciting a client certificate for client authentication. The
default value for the Advertised Certificate Authorities setting is None, indicating that no
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CAs are advertised. When set to None, no list of trusted CAs is sent to a client with the
certificate request. If the Client Certificate menu is set to Require or Request, you can
configure the Advertised Certificate Authorities setting to send clients a list of CAs that
the server is likely to trust. Like the Trusted Certificate Authorities list, the Advertised
Certificate Authorities drop down list includes the name of all the SSL certificates
installed in the BIG-IP /config/ssl/ssl.crt directory. A newly-installed BIG-IP system
includes the following certificates: default certificate and ca-bundle certificate. The
default certificate is a self-signed server certificate used for testing SSL profiles. This
certificate is not appropriate for use as an Advertised Certificate Authorities certificate
bundle. The ca-bundle certificate is a bundle of CA certificates from most of the wellknown PKIs around the world. This certificate may be appropriate for use as an
Advertised Certificate Authorities certificate bundle.
If you want to advertise only a specific CA or set of CAs, you should create and install a
bundle containing the certificates of the CA to advertise. Once you create this new
certificate bundle, you can select it in the Advertised Certificate Authorities setting drop
down menu.
You are allowed to configure the Advertised Certificate Authorities setting to send a
different list of CAs than that specified for the Trusted Certificate Authorities. This
allows greater control over the configuration information shared with unknown clients.
You might not want to reveal the entire list of trusted CAs to a client that does not
automatically present a valid client certificate from a trusted CA. Finally, you should
avoid specifying a bundle that contains a large number of certificates when you
configure the Advertised Certificate Authorities setting. This will cut down on the
number of certificates exchanged during a client SSL handshake. The maximum size
allowed by the BIG-IP for native SSL handshake messages is 14,304 bytes. Most
handshakes don't result in large message lengths, but if the SSL handshake is negotiating
a native cipher and the total length of all messages in the handshake exceeds the 14,304
byte threshold, the handshake will fail.
The Certificate Revocation List (CRL) setting allows you to specify a CRL that the BIG-IP
will use to check revocation status of a certificate prior to authenticating a client. If you
want to use a CRL, you must upload it to the /config/ssl/ssl.crl directory on the BIG-IP.
The name of the CRL file may then be entered in the CRL setting dialog box. Note that
this box will offer no drop down menu options until you upload a CRL file to the BIG-IP.
Since CRLs can quickly become outdated, you should use either OCSP or CRLDP profiles
for more robust and current verification functionality.
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Objective - 1.12 - Given a set of application requirements,
determine the appropriate virtual server type to use
1.12 - Given a set of application requirements, determine the appropriate
virtual server type to use
Link to Online Topic Content
You should expect to see many questions that involve knowing what type of virtual
server should be used in different scenarios, as well as, if a type were used what the
outcome would be. The following table lists the virtual server type options and defines
each virtual server type:
Virtual
server type
Description of virtual server type
Standard
A Standard virtual server directs client traffic to a load balancing pool
and is the most basic type of virtual server. It is a general purpose
virtual server that does everything not expressly provided by the other
type of virtual servers.
A Forwarding (Layer 2) virtual server typically shares the same IP
address as a node in an associated VLAN. A Forwarding (Layer 2)
virtual server is used in conjunction with a VLAN group.
A Forwarding (IP) virtual server forwards packets directly to the
destination IP address specified in the client request. A Forwarding
(IP) virtual server has no pool members to load balance.
A Performance (Layer 4) virtual server has a FastL4 profile associated
with it. A Performance (Layer 4) virtual server increases the speed at
which the virtual server processes packets.
A Performance (HTTP) virtual server has a FastHTTP profile
associated with it. The Performance (HTTP) virtual server and related
profile increase the speed at which the virtual server processes HTTP
requests.
A Stateless virtual server improves the performance of UDP traffic in
specific scenarios.
A Reject virtual server rejects any traffic destined for the virtual server
IP address.
A DHCP Relay virtual server relays DHCP client requests for an IP
address to one or more DHCP servers, and provides DHCP server
responses with an available IP address for the client. (11.1.0 and
later)
Forwarding
(Layer 2)
Forwarding (IP)
Performance
(Layer 4)
Performance
(HTTP)
Stateless
Reject
DHCP Relay
1.12 - Explain the security implications of adding service and/or protocol
profiles to a virtual server
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Profiles and security
Newer versions of TMOS have added features that will do protocol level inspection to
work in conjunction with profiles to provide security for the applications you Adding
protocol and service profiles to a virtual server help to provide additional level of
security for the traffic flowing through the BIG-IP platform. Each profile tells the virtual
server how to process the traffic according to the settings defined in the profile. This
can cause traffic, that is not following the protocol RFC or that is falling out of the guides
of the profile settings, to cause log level events or even break the flows.
1.12 - Differentiate between client side and server side settings
Client side and Server side
The concept of Client side and server side is important for most administrators to
understand. It concept is straight forward but very important to remember that in a full
proxy environment we need to think about the connections from client to server as
multiple connections and thus the actions that need to be taken or processing that has
to happen may need to be done in different ways on either side of the proxy.
A few of the profile settings in the configuration of a virtual server provide the option to
use a separate client side and server side profile. This gives the administrator the ability
to process traffic different on each side of the proxied connection for protocol level
traffic and for SSL termination and encryption. For example you could set a TCP profile
for a virtual server that is WAN optimized for the client side and LAN optimized for the
server side. This is better known as TCP express and is a very powerful function that the
BIG-IP can perform.
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Objective - 1.13 - Given a set of application requirements,
determine the appropriate virtual server configuration settings
1.13 - Describe which steps are necessary to complete prior to creating
the virtual server
Link to Online Topic Content
Configuring Virtual Servers
When creating virtual server objects in the config utility or the GUI you will need to do a
few tasks prior to jumping into building the virtual server. It is true that you can create a
simple virtual server in the GUI without doing anything prior because the GUI will allow
you to build the Pool and Node objects on the fly inside the virtual server creation task.
If you are creating a new virtual server in the config utility you will have to create all
necessary configuration objects that the virtual server will need to use for its creation.
It is always a good idea to have an established object naming convention figured out
prior to configuring any objects as well as a good understanding of IP addresses to be
used for the virtual server creation.
The objects you should create are as follows:
1.
2.
3.
4.
5.
6.
Health monitors for nodes and pool members
SNAT pools
Any necessary profiles
Any necessary iRules
Nodes that will be used in the pool members
Pool and pool members
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1.13 - Describe the security options when creating a virtual server (i.e.,
VLAN limitation, route domains, packet filters, iRules)
Virtual Server Security
A virtual server is essentially a listener that will be taking in and processing traffic on the
BIG-IP platform. Some of the biggest security risks when configuring a virtual server are
how it is listening, where it is listening and who can get to it. If you are configuring a
virtual server and not setting the necessary settings to restrict these areas of concern
you are opening your self up to security risks.
How Is The Virtual Server Listening?
The broader you set a virtual server to listen the greater the risk of unintended inbound
traffic. An application based virtual server should typically be configured to listen on the
default port for the application. For example if you are configuring a virtual server for a
new HTTP based website you would listen on port 80. If you listen on all ports (*), the
virtual server will take in traffic destine for the virtual server on all 65535 ports of the IP
address. And if the pool members for the virtual server are also listening on all ports (*),
it will send traffic to the servers on the port it arrived on the virtual server.
If you need to listen on multiple ports for the same IP address you can approach this in
two different ways. You can build a virtual server for each necessary port using the
same IP address or you can build one virtual server on all ports and use an iRule to
restrict the allowed inbound connections to your list of ports.
Where is the Virtual Server Listening?
When you configure a virtual server you tell the BIG-IP where you want it to listen for
traffic destined for the IP address of the virtual server. This virtual server setting is the
VLAN and Tunnel Traffic setting. By default the setting is set to All VLANs and Tunnels.
Which means the BIG-IP will listen on all VLANs. You are probably thinking, ARP is only
going to happen on the local subnet’s VLAN, which is true. So what can it possibly mean
to listen on all VLANs? When this setting is set to all VLANs it means that if traffic comes
to BIG-IP destined for the virtual server address from a VLAN that is not the VLAN of the
virtual server IP address, it will still take the traffic in on VLAN interface that it arrived
on. BIG-IP is a default deny device but in setting the setting to All VLANS and Tunnels
you have told the system to listen on all VLANs for traffic to the virtual server and allow
it in.
Link to Online Topic Content
Route Domains
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A route domain is a configuration object that isolates network traffic for a particular
application on the network.
Because route domains segment network traffic, you can assign the same IP address or
subnet to multiple nodes on a network, provided that each instance of the IP address
resides in a separate routing domain in the BIG-IP system. This feature will allow you to
isolate traffic and let upstream devices such as firewalls apply policy to the connections
between systems.
Link to Online Topic Content
Packet Filters
Packet filters enhance network security by specifying whether a BIG-IP system interface
should accept or reject certain packets based on criteria that you specify. Packet filters
enforce an access policy on incoming traffic. They apply to incoming traffic only.
You implement packet filtering by creating packet filter rules, using the BIG-IP
Configuration utility. The primary purpose of a packet filter rule is to define the criteria
that you want the BIG-IP system to use when filtering packets. Examples of criteria that
you can specify in a packet filter rule are:



The source IP address of a packet
The destination IP address of a packet
The destination port of a packet
You specify the criteria for applying packet filter rules within an expression. When
creating a packet filter rule, you can instruct the BIG-IP system to build an expression for
you, in which case you need only choose the criteria from predefined lists, or you can
write your own expression text, using the syntax of the tcpdump utility. For more
information on the tcpdump utility, see the online man page for the tcpdump
command.
You can also configure global packet filtering that applies to all packet filter rules that
you create. The following sections describe how to use the Configuration utility to set
global packet filtering options, as well as create and manage individual packet filters
rules.
Link to Online Topic Content
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iRules
You can use iRules to restrict traffic in almost anyway you can think of. You can set an
iRule to keep connections from happening when coming from a certain IP address range
or to a certain URI path in the HTTP request.
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Objective - 1.14 - Explain the matching order of multiple virtual
servers
1.14 - Explain the matching order of multiple virtual servers
Link to Online Topic Content
Virtual Server Matching Order
The BIG-IP system determines the order of precedence applied to new inbound
connections using an algorithm that places a higher precedence on the address netmask
and a lesser emphasis on the port. BIG-IP LTM sets virtual server precedence according
to the following criteria:




The first precedent of the algorithm chooses the virtual server that has the longest
subnet match for the incoming connection.
If the number of bits in the subnet mask match, the algorithm chooses the virtual server
that has a port match.
If no port match is found, the algorithm uses the wildcard server (if a wildcard virtual
server is defined).
A wildcard address has a netmask length of zero; thus, it has a lower precedence than
any matching virtual server with a defined address.
This algorithm results in the following order of precedence:






<address>:<port>
<address>:*
<network>:<port>
<network>:*
*:<port>
*:*
Example of VIP precedence behavior
For example, for a BIG-IP system with the following VIPs configured on the inbound
VLAN:
10.0.0.0/8:80
10.10.0.0/16:80
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66
10.10.10.10/32:80
20.0.0.0/8:*
20.0.0.0/8:80
*:80 (alternatively noted as 0.0.0.0/0:80)
*:* (alternatively noted as any:any, 0.0.0.0/0:any)
The following table illustrates how inbound destination addresses map to the
configured VIPs:
Inbound destination address
VIP
10.10.10.10:80
10.10.10.11:80
10.10.10.10/32:80 - address match and port match
10.10.0.0/16:80 - most specific address match and port
match
10.0.0.0/8:80 - most specific address match and port match
20.0.0.0/8:80 - most specific address match and port match
20.0.0.0/8:* - most specific address match with wildcard
port
*:* - wildcard address and wildcard port
10.1.10.10:80
20.0.0.0:80
20.0.0.0:443
1.1.1.1:443
F5 301a - LTM Specialist: Architect, Setup & Deploy - Study Guide
Objective - 1.15 - Given a scenario, determine the appropriate
load balancing method(s)
1.15 - Identify the behavior of the application to be load balanced
Application behavior
The key to choosing which load balancing method to use for an application, is to
understand the behavior of the application. What understanding the behavior really
means is, to understand how users access and use the application. Every application
will have somewhat different client access behaviors. You will need to gather as much
information as you can to gain an understanding of how the application is used.
Sometimes this may mean using the application yourself.
If the application is used the same by every user, and the amount of data transmitted
and length of the connection time to the application is the same for every user; then
Round Robin will likely work well for the application. If you have disparate hardware all
servicing the same application you may want to use a ratio based algorithm.
But as the transmitted size of the content and length of the session varies more you will
need to move to dynamic algorithms. Dynamic load balancing methods take into
account one or more dynamic factors, such as current connection count or even server
system performance. Because each application is unique, and distribution of load can
depend on a number of different factors, it is recommend that you experiment with
different load balancing methods, and select the one that offers the best performance
in your particular application.
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1.15 - Differentiate different load balancing methods
Link to Online Topic Content
Load Balancing Methods
There are many different types of load balancing algorithms that can be used to decide
how connections are distributed across a group of servers that are hosting an
application or service. All of these can be grouped into two different types of
algorithms, static and dynamic.
Some examples of static load balancing algorithms are Round-Robin and Ratio. These
types of algorithms do not take any environmental information into consideration and
simply do what they are defined to do for connection distribution. Round-Robin may
work well for short-lived, simple connections that return about the same amount of
data in all responses. Ratio is typically used when the servers in the group are not all of
equal capacity, or licensing levels differ per server and an uneven load should go to one
server over the other in the group.
Some examples of dynamic load balancing algorithms are least connections and fastest.
These types of algorithms can be affected by environmental information and use that
information to make a better server choice. Least Connections looks at current
connection counts at Layer 4 to the server and choses the server with the least
connections. Fastest looks at the outstanding Layer 7 request and choses the server
with the lowest amount.
Local Traffic Manager load balancing methods
Method
Description
Round Robin
This is the default load balancing
method. Round Robin mode
passes each new connection
request to the next server in line,
eventually distributing
connections evenly across the
array of machines being load
balanced.
Ratio (member) Local Traffic Manager distributes
Ratio (node)
connections among pool
members or nodes in a static
rotation according to ratio
weights that you define. In this
case, the number of connections
that each system receives over
time is proportionate to the ratio
When to use
Round Robin mode works well in
most configurations, especially if
the equipment that you are load
balancing is roughly equal in
processing speed and memory.
These are static load balancing
methods, basing distribution on
user-specified ratio weights that
are proportional to the capacity of
the servers.
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Dynamic Ratio
(member)
Dynamic Ratio
(node)
Fastest (node)
Fastest
(application)
Least
Connections
(member)
Least
Connections
weight you defined for each pool
member or node. You set a ratio
weight when you create each
pool member or node.
The Dynamic Ratio methods
select a server based on various
aspects of real-time server
performance analysis. These
methods are similar to the Ratio
methods, except that with
Dynamic Ratio methods, the ratio
weights are system-generated,
and the values of the ratio
weights are not static. These
methods are based on
continuous monitoring of the
servers, and the ratio weights are
therefore continually changing.
Note: To implement Dynamic
Ratio load balancing, you must
first install and configure the
necessary server software for
these systems, and then install
the appropriate performance
monitor.
The Fastest methods select a
server based on the least number
of current sessions. These
methods require that you assign
both a Layer 7 and a TCP type of
profile to the virtual server.
Note: If the OneConnectTM
feature is enabled, the Least
Connections methods do not
include idle connections in the
calculations when selecting a
pool member or node. The Least
Connections methods use only
active connections in their
calculations.
The Least Connections methods
are relatively simple in that Local
Traffic Manager passes a new
connection to the pool member
or node that has the least
The Dynamic Ratio methods are
used specifically for load
balancing traffic to RealNetworks®
RealSystem® Server platforms,
Windows® platforms equipped
with Windows Management
Instrumentation (WMI), or any
server equipped with an SNMP
agent such as the UC Davis SNMP
agent or Windows 2000 Server
SNMP agent.
The Fastest methods are useful in
environments where nodes are
distributed across separate logical
networks.
The Least Connections methods
function best in environments
where the servers have similar
capabilities. Otherwise, some
amount of latency can occur.
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(node)
number of active connections.
Note: If the OneConnect feature
is enabled, the Least Connections
methods do not include idle
connections in the calculations
when selecting a pool member or
node. The Least Connections
methods use only active
connections in their calculations.
Weighted Least
Connections
(member)
Like the Least Connections
methods, these load balancing
methods select pool members or
nodes based on the number of
active connections. However, the
Weighted Least Connections
methods also base their
selections on server capacity.
The Weighted Least Connections
(member) method specifies that
the system uses the value you
specify in Connection Limit to
establish a proportional
algorithm for each pool member.
The system bases the load
balancing decision on that
proportion and the number of
current connections to that pool
member. For example,
member_a has 20 connections
and its connection limit is 100, so
it is at 20% of capacity. Similarly,
member_b has 20 connections
and its connection limit is 200, so
it is at 10% of capacity. In this
case, the system select selects
member_b. This algorithm
Weighted Least
Connections
(node)
For example, consider the case
where a pool has two servers of
differing capacities, A and B.
Server A has 95 active
connections with a connection
limit of 100, while server B has 96
active connections with a much
larger connection limit of 500. In
this case, the Least Connections
method selects server A, the
server with the lowest number of
active connections, even though
the server is close to reaching
capacity.
If you have servers with varying
capacities, consider using the
Weighted Least Connections
methods instead.
Weighted Least Connections
methods work best in
environments where the servers
have differing capacities.
For example, if two servers have
the same number of active
connections but one server has
more capacity than the other,
Local Traffic Manager calculates
the percentage of capacity being
used on each server and uses that
percentage in its calculations.
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Observed
(member)
Observed
(node)
Predictive
(member)
Predictive
(node)
requires all pool members to
have a non-zero connection limit
specified.
The Weighted Least Connections
(node) method specifies that the
system uses the value you specify
in the node's Connection Limit
setting and the number of
current connections to a node to
establish a proportional
algorithm. This algorithm
requires all nodes used by pool
members to have a non-zero
connection limit specified.
If all servers have equal capacity,
these load balancing methods
behave in the same way as the
Least Connections methods.
Note: If the OneConnect feature
is enabled, the Weighted Least
Connections methods do not
include idle connections in the
calculations when selecting a
pool member or node. The
Weighted Least Connections
methods use only active
connections in their calculations.
With the Observed methods,
nodes are ranked based on the
number of connections. The
Observed methods track the
number of Layer 4 connections to
each node over time and create a
ratio for load balancing.
The Predictive methods use the
ranking methods used by the
Observed methods, where
servers are rated according to
the number of current
connections. However, with the
Predictive methods, Local Traffic
Manager analyzes the trend of
the ranking over time,
determining whether a nodes
performance is currently
The need for the Observed
methods is rare, and they are not
recommended for large pools.
The need for the Predictive
methods is rare, and they are not
recommend for large pools.
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Least Sessions
improving or declining. The
servers with performance
rankings that are currently
improving, rather than declining,
receive a higher proportion of
the connections.
The Least Sessions method
selects the server that currently
has the least number of entries in
the persistence table. Use of this
load balancing method requires
that the virtual server reference a
type of profile that tracks
persistence connections, such as
the Source Address Affinity or
Universal profile type.
Note: The Least Sessions
methods are incompatible with
cookie persistence.
The Least Sessions method works
best in environments where the
servers or other equipment that
you are load balancing have
similar capabilities.
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1.15 - Explain how to perform outbound load balancing
Link to Online Topic Content
Outbound Load Balancing
You might find that as your network grows, or network traffic increases, you require an
additional connection to the Internet. You can use this configuration to add an Internet
connection to your existing network. The following illustration shows a network
configured with two Internet connections.
Illustration of ISP load balancing
ISP load balancing (Outbound Load Balancing)
Task summary for ISP load balancing
Creating a pool of outbound routers
You can a create load balancing pool, which is a logical set of devices, such as web
servers, that you group together to receive and process traffic, to efficiently distribute
the load on your resources. Using this procedure, create one pool to load balance the
routers.
1.
2.
3.
4.
On the Main tab, click Local Traffic > Pools. The Pool List screen opens.
Click Create. The New Pool screen opens.
In the Name field, type a unique name for the pool.
For the Health Monitors setting, in the Available list, select a monitor type, and
click << to move the monitor to the Active list.
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5. From the Load Balancing Method list, select how the system distributes traffic to
members of this pool. The default is Round Robin.
6. For the Priority Group Activation setting, specify how to handle priority groups:
 Select Disabled to disable priority groups. This is the default option.
 Select Less than, and in the Available Members field, type the minimum
number of members that must remain available in each priority group in
order for traffic to remain confined to that group.
7. Using the New Members setting, add each resource that you want to include in
the pool:
 Either type an IP address in the Address field, or select a node address from
the Node List.
 Type a port number in the Service Port field, or select a service name from
the list.
 To specify a priority group, type a priority number in the Priority field.
 Click Add.
8. Click Finished.
The load balancing pool appears in the Pools list.
Creating a virtual server for outbound traffic for routers
You must create a virtual server to load balance outbound connections. The default
pool that you assign as a resource in this procedure is the pool of routers.
1. On the Main tab, click Local Traffic > Virtual Servers. The Virtual Server List
screen displays a list of existing virtual servers.
2. Click the Create button. The New Virtual Server screen opens.
3. In the Name field, type a unique name for the virtual server.
4. Specify the Destination setting, using the Address field; type the IP address you
want to use for the virtual server. The IP address you type must be available and
not in the loopback network.
5. In the Resources area of the screen, from the Default Pool list, select a pool
name.
6. Click Finished.
The virtual server is configured to load balance outbound connections to the routers.
Creating self IP addresses an external VLAN
You must assign two self IP addresses to the external VLAN.
1. On the Main tab, click Network > Self IPs. The Self IPs screen opens.
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2. Click Create. The New Self IP screen opens.
3. In the IP Address field, type an IP address. This IP address should represent the
network of the router. The system accepts IP addresses in both the IPv4 and
IPv6 formats.
4. In the Netmask field, type the network mask for the specified IP address.
5. Select External from the VLAN list.
6. Click Repeat.
7. In the IP Address field, type an IP address. This IP address should represent the
address space of the VLAN that you specify with the VLAN/Tunnel setting. The
system accepts IP addresses in both the IPv4 and IPv6 formats.
8. Click Finished. The screen refreshes, and displays the new self IP address in the
list.
The self IP address is assigned to the external VLAN.
Enabling SNAT automap for internal and external VLANs
You can configure SNAT automapping on the BIG-IP system for internal and external
VLANs.
1. On the Main tab, click Local Traffic > SNATs. The SNAT List screen displays a list
of existing SNATs.
2. Click Create.
3. Name the new SNAT.
4. From the Translation list, select automap.
5. For the VLAN List setting, in the Available field, select external and external, and
using the Move button, move the VLANs to the Selected field.
6. Click Finished.
SNAT automapping on the BIG-IP system is configured for internal and external VLANs.
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1.15 - Explain CARP persistence
Link to Online Topic Content
CARP Persistence
The hash persistence profile can perform a pool member selection using a stateless hash
algorithm based on the Cache Array Routing Protocol (CARP). Additionally, starting in
BIG-IP 10.2.0, the source address affinity and destination address affinity persistence
profiles can also perform pool member selection using a stateless hash algorithm based
on CARP. The CARP algorithm was originally described in an IETF draft, which is
available at the following location:
http://tools.ietf.org/html/draft-vinod-carp-v1-03
The CARP algorithm provides the following advantages over stateful persistence
methods:

No memory storage required
The CARP algorithm uses a stateless selection; therefore, it does not use the
persistence table, which is stored in memory.
Note: Since the CARP algorithm does not store persistence records, commands such as
tmsh show /ltm persistence persist-records and bigpipe persist show all cannot be used
to monitor CARP persistence.

No timeout
Since the CARP algorithm does not use the persistence table, there is no timeout
associated.

Failover without mirroring
Since the CARP persistence method uses a stateless election, no mirroring of
persistence data is required in order to maintain persistence after a failover
event.

Automatic redistribution
Since the CARP algorithm is based on available pool members, the algorithm
automatically adjusts as pool members become available or unavailable, and has
the benefit of reducing the percentage of cache misses compared with the
default hash algorithm. For example, if you have a pool of four HTTP cache
servers, and one server goes offline, the CARP algorithm will redistribute those
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requests to the remaining servers. Therefore, only connections that were going
to that one server will be redistributed. Additionally, when that server is
brought back online, only those requests that were originally sent to that server
will be directed back. In the case of the default hash algorithm, all requests will
be randomly redistributed across the remaining servers each time a server
transitions from offline to online.
CARP is an excellent choice for load balancing a pool of HTTP cache proxies, when used
in combination with the HTTP and OneConnect profiles. However, the CARP algorithm is
not limited to HTTP traffic. Other applications, which are compatible with stateless
persistence, may also benefit from the advantages listed above.
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Objective - 1.16 - Explain the effect of LTM device configuration
parameters on load balancing decisions
1.16 - Differentiate between members and nodes
Link to Online Topic Content
Nodes vs Members
A node is a logical object on the BIG-IP Local Traffic Manager system that identifies the
IP address of a physical resource on the network. You can explicitly create a node, or
you can instruct Local Traffic Manager to automatically create one when you add a pool
member to a load balancing pool.
The difference between a node and a pool member is that a node is designated by the
devices IP address only (10.10.10.10), while designation of a pool member includes an IP
address and a service (such as 10.10.10:80).
A primary feature of nodes is their association with health monitors. Like pool
members, nodes can be associated with health monitors as a way to determine server
status. However, a health monitor for a pool member reports the status of a service
running on the device, whereas a health monitor associated with a node reports status
of the device itself.
For example, if an ICMP health monitor is associated with node 10.10.10.10, which
corresponds to pool member 10.10.10.10:80, and the monitor reports the node as being
in a down state, then the monitor also reports the pool member as being down.
Conversely, if the monitor reports the node as being in an up state, then the monitor
reports the pool member as being either up or down, depending on the status of the
service running on it.
Nodes are the basis for creating a load balancing pool. For any server that you want to
be part of a load balancing pool, you must first create a node, that is, designate that
server as a node. After designating the server as node, you can add the node to a pool
as a pool member. You can also associate a health monitor with the node, to report the
status of that server.
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1.16 - Explain the effect of the load balancing method on the LTM
platform
Link to Online Topic Content
Load Balancing Method Effect on LTM
The function of load balancing traffic based on the processing of an algorithm against
the available pool members will uses system resources. Each algorithm may use a
different amount of system resources. Static load Balancing methods will tend to use
fewer resources than a more advanced dynamic algorithm. However if a more
advanced method is needed to distribute the application connections across the servers
then that is what should be used. The additional overhead will likely be nominal to the
overall system performance. If you are using a method that could be done with a less
complex algorithm then you should step it down to that algorithm.
For Example:
The Ratio load balancing method uses an algorithm that is more CPU intensive than the
algorithm used by the Round Robin load balancing method. For this reason, you should
use the Ratio load balancing method only when different node or pool member weights
are required. For example, you should modify a pool that distributes connections
among four pool members in a static rotation according to a 1:1:1:1 ratio to use the
Round Robin load balancing method. In large configurations, this method can
significantly reduce the CPU load.
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1.16 - Explain the effect of CMP on load balancing methods
Link to Online Topic Content
CMP Effects Load Balancing Methods
CMP should not be confused with Symmetric Multi-Processing (SMP). SMP architecture
is used in multiple operating systems. SMP operates by allowing operating systems and
software applications that are optimized for SMP to use the multiple processors
available to the operating system. SMP performs this operation by spreading multiple
threads across multiple processors, which allows for faster processing and more
efficient use of system resources, as multiple threads can be processed simultaneously
instead of waiting in a queue to be processed. CMP uses a similar approach to leverage
multiple processing units by spawning a separate instance of the TMM process on each
processing unit available to the system. While SMP may be used for any process, CMP
processing is available only to the BIG-IP TMM process for the sole purpose of providing
more dedicated resources to manage load balanced traffic. With multiple TMM
instances simultaneously processing traffic, system performance is enhanced, and traffic
management capacity is expanded.
The CMP feature is automatically enabled on CMP-capable platforms, ensuring that all
instances of TMM are available to process application traffic as follows:



2 TMM processes running on a dual-CPU BIG-IP 8400 system
4 TMM processes running on a dual-core, dual-CPU BIG-IP 8800 system
32 TMM processes running on a VIPRION platform with four 2100 blades
Load balancing behavior on CMP enabled virtual servers
Connections on a CMP enabled virtual server are distributed among the available TMM
processes. The load balancing algorithm, specified within the pool associated with the
CMP enabled virtual server, is applied independently in each TMM. Since each TMM
handles load balancing independently from the other TMMs, distribution across the
pool members may appear to be incorrect when compared with a non-CMP enabled
virtual server using the same load balancing algorithm.
Consider the following example configuration:
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Virtual Server: 172.16.10.10:80
Pool with 4 members: 10.0.0.1:80
10.0.0.2:80
10.0.0.3:80
10.0.0.4:80
Pool Load Balancing Method: Round Robin
Scenario 1: Virtual server without CMP enabled
Four connections are made to the virtual server. The BIG-IP system load balances the
four individual connections to the four pool members based on the Round Robin load
balancing algorithm:
--Connection 1--> |
| --Connection 1--> 10.0.0.1:80
--Connection 2--> |-> BIG-IP Virtual Server ->| --Connection 2--> 10.0.0.2:80
--Connection 3--> |
| --Connection 3--> 10.0.0.3:80
--Connection 4--> |
| --Connection 4--> 10.0.0.4:80
Scenario 2: Virtual server with CMP enabled on a BIG-IP 8800
Four connections are made to the virtual server, unlike the first scenario where CMP
was disabled, the BIG-IP distributes the connections across the multiple TMM processes.
The BIG-IP 8800 with CMP enabled can use four TMM processes. Since each TMM
handles load balancing independently of the other TMM processes, it is possible that all
four connections are directed to the same pool member.
--Connection 1--> |
| --Connection 1--> TMM0 --> 10.0.0.1:80
--Connection 2--> |-> BIG-IP Virtual Server ->| --Connection 2--> TMM1 --> 10.0.0.1:80
--Connection 3--> |
| --Connection 3--> TMM2 --> 10.0.0.1:80
--Connection 4--> |
| --Connection 4--> TMM3 --> 10.0.0.1:80
The CMP feature is designed to speed up connection handling by distributing
connections across multiple TMM processes. While initially this behavior may appear to
favor one or several servers, over time the load will be distributed equally across all
servers.
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1.16 - Explain the effect of OneConnect/MBLB on load balancing
Link to Online Topic Content
OneConnect
The BIG-IP OneConnect feature can increase network throughput by efficiently
managing connections created between the BIG-IP system and back end nodes.
OneConnect allows the BIG-IP system to minimize the number of server-side TCP
connections by making existing idle connections available for reuse by other clients. The
OneConnect source mask setting manages connection reuse, and is applied to the
server-side source IP address of a request to determine its eligibility for connection
reuse.
Overview of the OneConnect Mask
OneConnect applies a mask (much like applying an independent subnet mask) to client
source IP addresses on server-side connections. This mask determines the availability of
an existing idle TCP connection for the request on the selected destination server. The
following list displays the idle TCP port reuse behavior. To simplify things, regarding
these explanations, F5 assumes that a previous TCP request has established a
connection on the destination server, the connection is idle, and the same destination
server has been selected for a subsequent client request.
OneConnect
Mask
255.255.255.255
255.255.255.0
255.255.0.0
255.0.0.0
0.0.0.0
OneConnect masking behavior
The entire client IP address is evaluated. A request from the same
address reuses an established idle TCP connection.
Octets 1-3 are evaluated client addresses matching this subset and
reuse an existing idle TCP connection.
Client addresses are evaluated based on the first and second octets
when selecting an idle TCP connection for reuse.
Only the first octet of a client IP address is evaluated when selecting
an idle TCP connection for reuse.
The all zeros mask (the default setting) looks for any open idle TCP
connection on the destination server. The main difference is
OneConnect does not attempt to group the request based on octets
matched, but uses open idle TCP connections in a highly efficient
manner.
Effects of modifying the source mask
The following three scenarios describe the effects of using different source masks:
Using a OneConnect profile with a 0.0.0.0 source mask
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A OneConnect profile with a source mask of 0.0.0.0 shares idle connections across all
client requests in the following manner:





Client A with source IP address 10.10.10.10 connects to a virtual server.
The BIG-IP system load-balances the connection and applies the source mask to
the request on the server-side flow, finds no suitable connection for reuse, and
creates a TCP connection to server A in the pool.
Client B with source IP address 10.20.20.20 connects to the same virtual server.
The BIG-IP system load-balances the connection, applies the source mask to the
server-side flow, and finds an eligible idle TCP connection.
The BIG-IP system aggregates the request from client B over the existing TCP
connection created for client A.
Using a OneConnect profile with a 255.255.255.0 source mask
A OneConnect profile with a source mask of 255.255.255.0 aggregates connections from
client IP addresses sharing the same last octet in the following manner:








Client A with a source IP address of 10.10.10.10 connects to a virtual server.
The BIG-IP system load-balances the connection and applies the source mask to
the request on the server-side flow, finds no suitable connection for reuse, and
creates a TCP connection to server A in the pool.
Client B with a source IP address of 10.10.10.100 connects to the same virtual
server.
The BIG-IP system load-balances the connection, applies the source mask to the
server-side flow, and finds an eligible idle TCP connection.
The BIG-IP system aggregates the request from client B over the existing TCP
connection created for client A.
Client C with source IP address 10.10.20.10 connects to the same virtual server.
The BIG-IP system load-balances the connection, applies the source mask to the
server-side flow, and finds no suitable connection for reuse.
The BIG-IP system creates a new TCP connection to the selected pool member.
Using a OneConnect profile with a 255.255.255.255 source mask
A OneConnect profile with a source mask of 255.255.255.255 will only aggregate
connections originating from the same server-side client IP address.
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1.16 - Explain how monitors and load balancing methods interact
Link to Online Topic Content
Monitors and Load Balancing Methods
The BIG-IP system is designed to distribute client requests to load balancing pools
composed of multiple servers. Factors such as the BIG-IP configuration, server
performance, and network-related issues determine the pool member to which the BIGIP system sends the connection, and whether connections are evenly distributed across
BIG-IP pool members. For example, a virtual server referencing a Round Robin pool will
distribute connections across BIG-IP pool members evenly over time. However, if the
same virtual server also references a BIG-IP configuration object that affects traffic
distribution such as a OneConnect profile or an iRule, connections may not be evenly
distributed, as expected.
Factors affecting traffic distribution across pool members are discussed below.
Load balancing methods
The load balancing algorithm is the primary mechanism that determines how
connections are distributed across pool members. You can define static or dynamic load
balancing methods for a pool. Certain load balancing methods are designed to
distribute requests evenly across pool members, and other load balancing methods are
designed to favor higher performing servers, possibly resulting in uneven traffic
distribution across pool members.
Static load balancing methods
Certain static load balancing methods are designed to distribute traffic evenly across
pool members. For example, the Round Robin load balancing method causes the BIG-IP
system to send each incoming request to the next available member of the pool,
thereby distributing requests evenly across the servers in the pool. However, when a
static load balancing method such as Round Robin is used along with a BIG-IP
configuration object that affects load distribution, such as a OneConnect profile or a
persistence profile, traffic may not be evenly distributed across BIG-IP pool members as
expected.
Dynamic load balancing methods
Dynamic load balancing methods typically favor higher performing servers, and may
result in uneven traffic distribution across pool members. Dynamic load balancing
methods are designed to work with servers that differ in processing speed and memory.
For example, when a dynamic load balancing method such as the Observed method is
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defined for a pool, higher performing servers will process more connections over time
than lower performing servers. As a result, connection statistics for the higher
performing servers will exceed those for lower performing severs.
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Section 2 - Set-up, administer, and secure LTM devices
Objective - 2.01 Distinguish between the management interface
configuration and application traffic interface configuration
2.01 - Explain the requirements for management of the LTM devices
Link to Online Topic Content
LTM Management
The BIG-IP can be managed through either the TMM switch interfaces or the MGMT
interface. However, F5 recommends that you use the management port.
The TMM switch ports are the interfaces that the BIG-IP system uses to send and
receive load-balanced traffic.
The system uses the MGMT interface to perform system management functions. The
MGMT interface is intended for administrative traffic and cannot be used for loadbalanced traffic. Additionally, since no access controls can be applied on the MGMT
interface, F5 recommends that you limit network access through the MGMT interface to
trusted traffic. For security reasons, the MGMT interface should be connected to only a
secure, management-only network, such as one that uses an RFC1918 private IP address
space. If you do not have a trusted and secure management network, F5 recommends
that you do not use the MGMT interface, and that you grant administrative access
through the TMM switch interfaces or the local serial console.
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2.01 - Explain the requirements for the application traffic traversing the
LTM devices
Link to Online Topic Content
Requirements for Application Traffic to Traverse the LTM
The BIG-IP system must be connected to a client accessible network as well as the server
network. These networks may be one in the same or separate networks in your
environment. The BIG-IP should have a default gateway configured. The client will
access the application via a virtual server configured on the client side network. The
virtual server will pass traffic to a pool member configured in the pool associated to the
virtual server. This will send the traffic to the server defined as the pool member. The
server will receive the traffic and process it as necessary. The server will respond to the
client of the connection. The traffic will need to pass back through the BIG-IP to be
processed back to the client correctly. If the server has a default path back to the client
that does not traverse the BIG-IP platform the communication will fail. If this is the case
a SNAT of the clients source IP address will correct this issue. If the servers default path
to the client is through the BIG-IP the system will handle rewriting the packet back to
the client correctly.
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2.01 - Explain how to configure management connectivity options: AOM,
serial console, USB & Management Ethernet Port
Link to Online Topic Content
USB
On rare occasions, you may be required to perform a clean installation of BIG-IP 11.x.
During a clean installation, all mass-storage devices are wiped, therefore restoring the
BIG-IP system to its factory defaults. In addition, a clean installation allows you to
reinstall a BIG-IP unit that no longer boots from any of its boot locations.
You should choose an installation method based on the equipment available to you, and
whether you have physical access to the system that requires reinstalling. Choose one
of the following installation methods, which are listed in order of preference:
USB DVD-ROM drive
Note: F5 recommends that you perform a clean installation by using a USB DVD-ROM drive,
as this is the simplest and most reliable of all the installation methods.
USB thumb drive
Burn the product ISO image to a DVD.
Image the USB thumb drive using the product ISO image file.
Installing the software
1. Connect to the BIG-IP system serial console.
2. Depending on the choice you made in the previous procedure, perform one of
the following actions:
◦ Connect the USB DVD-ROM drive to the F5 system and load the disc you
burned with the product ISO image.
◦ Connect the USB thumb drive to the F5 system..
3. Reboot the BIG-IP system. If the F5 system cannot reboot, power cycle the BIGIP system.
Note: Upon completion of this step, regardless of the installation method, the BIG-IP
system boots into the Maintenance Operating System (MOS).
4. The MOS asks you to specify the type of terminal you are using. If you do not
know what to specify, press Enter. The default setting (vt100) is fine in most
cases.
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5. If you have booted the F5 system from a USB device, the system may display a
manufacturing installation dialog.
6. Press Ctrl+C to exit the dialog.
7. Continue with step 8 if you have booted the F5 system from a USB removable
media containing a BIG-IP 11.0.0 image, but you want to perform a custom
installation using the diskinit and image2disk utilities. Otherwise, to reinstall the
system according to the manufacturing installation plan displayed in the output,
press Enter and skip to step 10.
8. To wipe all mass-storage devices inside the BIG-IP system, type the following
command:
diskinit --style volumes
Important: Do not omit the --style option; if you omit it, the system wipes the drives but
does not reformat them.
9. The diskinit utility asks whether you want to proceed wiping the drives. To
continue, type y and press Enter. Otherwise, type n and press Enter.
Important: Confirming this operation destroys all data on the system. Do not proceed
with this step if you have data that needs to be recovered from the system. Using the
MOS, you may be able to manually mount a partition or volume and recover such data.
10. Install the software using one of the following methods:
◦ If you are using a USB DVD-ROM drive or a USB thumb drive, use the
following command:
image2disk --format=volumes --nosaveconfig --nosavelicense
◦
If you are using a PXE server, use the following command syntax:
image2disk --format=volumes --nosaveconfig --nosavelicense
http://<SERVER_IP>/<PATH>
For example, to install BIG-IP 11.x on HD1.1 using the http server configured
in the previous procedure, type the following command:
image2disk --format=volumes --nosaveconfig --nosavelicense
http://192.168.1.1/SOL13117
Note: BIG-IP 11.x cannot be installed on a CompactFlash media drive; you must use boot
locations on the system’s hard drive.
Note: You must specify the --nosaveconfig option, as the system does not have a
configuration to save.
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Note: If you are using a USB DVD-ROM drive or a USB thumb drive, you do not need to
specify an installation repository, as the image2disk utility automatically finds and
defaults to /cdserver.
Note: For more information about the image2disk utility, refer to the Help screen by
using the image2disk --h command.
11. Once the installation has completed, disconnect any removable media from the
BIG-IP system.
12. To restart the system, type the following command:
reboot
The system boots from the location you have just reinstalled.
Link to Online Topic Content
Serial Console
You can administer a BIG-IP system by using a null modem cable to connect a
management system that runs a terminal emulator program to the BIG-IP serial port. To
connect to the BIG-IP system using the serial port, you must have a DB9 null modem
cable and a VT100-capable terminal emulator available on the management system.
To configure a serial terminal console for the BIG-IP system, perform the following
procedure:
1. Connect the null modem cable to the console port on the BIG-IP system.
2. Connect the null modem cable to a serial port on the management system with
the terminal emulator.
3. Configure the serial terminal emulator settings according to the following table:
Setting
Value
Bits per second [baud]
Data bits
Parity
Stop bit
Flow control
19200
8
None
1
None
4. Turn on the BIG-IP system.
When the BIG-IP system starts up with the console working correctly, the system startup sequence displays, and then the sequence completes with a BIG-IP system login
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prompt. If garbled text displays on the console, you may be required to change the
baud of the serial console port using the LCD panel on the BIG-IP system.
Link to Online Topic Content
Management Ethernet Port
The management port on a BIG-IP system provides administrative access to the system
out-of-band of the application traffic. This allows you to restrict administrative access
to an internal secure network. You can display and configure the management IP
address for the BIG-IP system using the Configuration utility, the command line, and the
LCD panel.
Configuring the management IP address using the Configuration utility, command line,
or LCD panel
You can configure the management IP address using the Configuration utility, the tmsh
utility, the config command, or the LCD panel. To do so, perform one of the following
procedures:
Impact of procedure: Changing the management IP address will disconnect you from the
BIG-IP system if you are connected through the management port.
Configuring the management IP address using the Configuration utility
1. Log in to the Configuration utility.
2. Navigate to System > Platform.
3. In the Management Port section, configure the IP address, network mask, and
management route.
4. To save the changes, click Update.
Configuring the management IP address using the tmsh utility
1. Log in to the Traffic Management Shell (tmsh) by typing the following command:
tmsh
2. To configure the management IP address, use the following syntax:
create /sys management-ip [ip address/netmask]
or
create /sys management-ip [ip addres/prefixlen]
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For example:
create /sys management-ip 192.168.1.245/255.255.255.0
or
create /sys management-ip 192.168.1.245/24
3. To configure a default management gateway, use the following syntax:
create /sys management-route default gateway <gateway ip address>
For example:
create /sys management-route default gateway 192.168.1.254
4. Save the changes by typing the following command:
save /sys config partitions all
Configuring the management IP address using the config command
1. Log in to the command line of the BIG-IP system.
2. Enter the F5 Management Port Setup Utility by typing the following command:
config
3. To configure the management port, type the appropriate IP address, netmask,
and management route in the screens that follow.
Configuring the management IP address using the LCD panel
1.
2.
3.
4.
5.
6.
7.
8.
9.
Press the X button to activate Menu mode for the LCD.
Use the arrow keys to select System, and press the Check button.
To select Management, press the Check button.
To select Mgmt IP, press the Check button.
Enter your management IP address using the arrow keys, and press the Check
button.
Use the arrow keys to select Mgmt Mask, and press the Check button.
Enter the netmask using the arrow keys, and press the Check button.
Use the arrow keys to select Mgmt Gateway, and press the Check button.
Enter your default route using the arrow keys, and press the Check button.
If you do not have a default route, enter 0.0.0.0.
10. Use the arrow keys to select Commit, and press the Check button.
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11. To select OK, press the Check button.
Link to Online Topic Content
AOM
Always-On Management (AOM) is a separate subsystem that provides lights-out
management for the BIG-IP system by using the 10/100/1000 Ethernet management
port over secure shell (SSH), or by using the serial console.
AOM allows you to manage BIG-IP platforms using SSH (most platforms) or the serial
console, even if the Host subsystem is turned off. The BIG-IP Host subsystem and the
AOM subsystem operate independently. If AOM is reset or fails, the BIG-IP Host
subsystem continues to operate and there is no interruption to load-balanced traffic.
AOM is always turned on when power is supplied to the platform. If the BIG-IP Host
subsystem stops responding, you can use the AOM Command Menu to reset it.
Configuring AOM network access
To configure AOM so that it can be accessed over the network, perform the following
procedure:
Impact of procedure: Performing the following procedure should not have a negative
impact on your system.
1. Connect the serial console to the CONSOLE port.
2. Display the AOM command menu by typing the following key sequence:
Esc (
The AOM command menu displays as follows:
AOM Command Menu:
B --- Set console baud rate
I --- Display platform information
P --- Power on/off host subsystem
R --- Reset host subsystem
N --- Configure AOM network
S --- Configure SSH Server
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A --- Reset AOM
E --- Error report
Q --- Quit menu and return to console
3. To configure network access, press the N key.
The AOM management network configurator screen appears.
4. Complete the network configurator screens.
Important: The AOM IP address must be different than the BIG-IP management address,
but on the same IP subnet.
5. To disable the network configuration, re-run the N ---Configure AOM network
option, and enter 0.0.0.0 for the IP address.
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Objective - 2.02 Given a network diagram, determine the
appropriate network and system settings (i.e., VLANs, selfIPs,
trunks, routes, NTP servers, DNS servers, SNMP receivers and
syslog servers)
2.02 - Explain the requirements for self IPs (including port lockdown)
Link to Online Topic Content
Self IPs
As stated previously, it is when you initially run the Setup utility on a BIG-IP system that
you normally create any static and floating self IP addresses and assign them to VLANs.
However, if you want to create additional self IP addresses later, you can do so using the
Configuration utility.
Note: Only users with either the Administrator or Resource Administrator user role can
create and manage self IP addresses.
Note: A self IP address can be in either IPv4 or IPv6 format.
IP address
As described in Introduction to self IP addresses, a self IP address, combined with a
netmask, typically represents a range of host IP addresses in a VLAN. If you are
assigning a self IP address to a VLAN group, the self IP address represents the range of
self IP addresses assigned to the VLANs in that group.
Netmask
When you specify a netmask for a self IP address, the self IP address can represent a
range of IP addresses, rather than a single host address. For example, a self IP address
of 10.0.0.100 can represent several host IP addresses if you specify a netmask of
255.255.0.0.
VLAN/Tunnel assignment
You assign a unique self IP address to a specific VLAN or a VLAN group:

Assigning a self IP address to a VLAN
The self IP address that you assign to a VLAN should represent an address space that
includes the self IP addresses of the hosts that the VLAN contains. For example, if the
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address of one destination server in a VLAN is 10.0.0.1 and the address of another
server in the VLAN is 10.0.0.2, you could assign a self IP address of 10.0.0.100, with a
netmask of 255.255.0.0, to the VLAN.

Assigning a self IP address to a VLAN group
The self IP address that you assign to a VLAN group should represent an address space
that includes the self IP addresses of the VLANs that you assigned to the group. For
example, if the self IP address of one VLAN in a VLAN group is 10.0.20.100 and the
address of the other VLAN in a VLAN group is 10.0.30.100,you could assign an address of
10.0.0.100, with a netmask of 255.255.0.0, to the VLAN group.
The VLAN/Tunnel list in the BIG-IP Configuration utility displays the names of all existing
VLANs and VLAN groups.
Port lockdown
Each self IP address has a feature known as port lockdown. Port lockdown is a security
feature that allows you to specify particular UDP and TCP protocols and services from
which the self IP address can accept traffic. By default, a self IP address accepts traffic
from these protocols and services:


For UDP, the allowed protocols and services are: DNS (53), SNMP (161), RIP (520)
For TCP, the allowed protocols and services are: SSH (22), DNS (53), SNMP (161),
HTTPS (443), 4353 (iQuery)
If you do not want to use the default setting (Allow Default), you can configure port
lockdown to allow either all UDP and TCP protocols and services (Allow All), no UDP
protocols and services (Allow None), or only those that you specify (Allow Custom).
Traffic groups
If you want the self IP address to be a floating IP address, that is, an address shared
between two or more BIG-IP devices in a device group, you can assign a floating traffic
group to the self IP address. A floating traffic group causes the self IP address to
become a floating self IP address.
A floating self IP address ensures that application traffic reaches its destination. More
specifically, a floating self IP address enables a source node to successfully send a
request, and a destination node to successfully send a response, when the relevant BIGIP device is unavailable.
If you want the self IP address to be a static (non-floating) IP address (used mostly for
standalone devices), you can assign a non-floating traffic group to the self IP address. A
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non-floating traffic group causes the self IP address to become a non-floating self IP
address. An example of a non-floating self IP address is the address that you assign to
the default VLAN named HA, which is used strictly to process failover communications
between BIG-IP devices, instead of processing application traffic.
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2.02 - Explain routing requirements for management and application
traffic (including route domains and IPv6)
Link to Online Topic Content
The Traffic Management Microkernel (TMM) controls all of the BIG-IP switch ports
(TMM interfaces), and the underlying Linux operating system controls the BIG-IP
management interface. The management interface processes only administrative
traffic. The TMM interfaces process both application traffic and administrative traffic.
Traffic type
The BIG-IP system can process the following traffic types:
Application traffic
TMM processes inbound application traffic that arrives on a TMM switch interface and
is destined for a BIG-IP self IP address or a virtual server address.
Administrative traffic
BIG-IP administrative traffic can be defined as follows:

Inbound administrative connections
Inbound connections sent to the BIG-IP management IP address that arrive on
the management interface are processed by the Linux operating system.
Inbound connections sent to the BIG-IP self IP addresses that arrive on a TMM
interface are processed by TMM. If the self IP address is configured to allow a
connection to the destination service port, TMM hands the connection off to the
Linux operating system, which then processes the connection request.

Outbound administrative connections
Outbound connections sent from the BIG-IP system by administrative
applications (SNMP, SMTP, SSH, NTP, etc.) are processed by the Linux operating
system. These connections may use either the management address or a self IP
address as the source address. The BIG-IP system compares the destination
address to the routing table to determine the interface through which the BIG-IP
system routes the traffic.
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Note: This behavior applies to only unsolicited outbound traffic: traffic that is not in
response to a request originated by a remote host. A response to a request originated by a
remote host is returned to the last MAC address traversed by the inbound request.
Note: You can configure a health monitor to send probes using the management network.
However, F5 strongly discourages this configuration because the management network is
not intended for production traffic. F5 recommends that the pool members/nodes reside
on a network that is reachable through TMM interfaces so that health monitor probes are
sent through TMM interfaces.
BIG-IP routing tables
The BIG-IP routing table consists of the following routing subtables:
Management routes
Management routes are routes that the BIG-IP system uses to forward traffic through
the management interface. For traffic sourced from the management address, the
system prefers management routes over TMM routes, and uses the most specific
matching management route. If no management route is defined or matched, the
system uses the most specific matching TMM route.
TMM routes
TMM switch routes are routes that the BIG-IP system uses to forward traffic through the
TMM switch interfaces instead of through the management interface. Routes in the
TMM subtable are defined with a lower metric than routes in the management
subtable. Traffic sourced from a TMM (self IP) address will always use the most specific
matching TMM route. Traffic sourced from a TMM address will never use a
management route. When TMM is not running, the TMM addresses are not available,
and all TMM routes are removed. As a result, when TMM is not running, all outbound
administrative traffic uses the most specific matching management route.
F5 recommends that you add static routes for management traffic whose destination
does not match the directly-connected management network. This configuration is
useful when you handle SNMP traffic that is directed to an SNMP Manager that resides
on another network, which is accessible only through the management network or
other network services that are hosted on networks that are not accessible by way of
the TMM interfaces.
The BIG-IP system can act as a full proxy and termination point providing application
availability, bi-directional address translation, authentication and security services, and
DNS services that cross IPv4 and IPv6 network boundaries.
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2.02 - Explain the effect of system time on LTM devices
Link to Online Topic Content
Time
Having the correct system time set on your BIG-IP devices is critical for many different
administrative functions. Time stamping for logging is all based on system time. SSL
certificates could have issues with the expiration dates. In HA environments if the
system time is not set correctly between the units in the HA configuration the systems
may not be able to sync configs.
When the BIG-IP system clock is not showing the correct timezone, or the date and time
is not synchronized correctly, this could be caused by incorrect NTP configuration or a
communication issue with a valid NTP peer server. Remember that even if you have the
NTP settings correct in the BIG-IP system it may not be able to reach the NTP if there is
an up stream Firewall or other network restrictions.
Network Time Protocol (NTP)
NTP is a protocol for synchronizing the clocks of computer systems over the network.
On BIG-IP systems, accurate timestamps are essential to guarantee the correct behavior
of a number of features. While in most cases it is sufficient to configure a couple of time
servers that the BIG-IP system will use to update its system time, it is also possible to
define more advanced NTP configurations on the BIG-IP system.
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Objective - 2.03 Given a network diagram, determine the
appropriate physical connectivity
2.03 - Explain physical network connectivity options of LTM devices
Link to Online Topic Content
Networking Device
Depending on the model of BIP-IP platform you are working with, you will find different
counts and types of network interfaces. The image below describes the different
interfaces on the typical BIG-IP platform. Interface count will vary per model.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Management port
USB ports
Console port
Serial (hard-wired) failover port
10/100/1000 interfaces
SFP ports
Indicator LEDs
LCD display
LCD control buttons
Physical Connections
Management Port
Every BIG-IP system has a management port. The management port is a special
interface that the BIG-IP system uses to receive or send certain types of administrative
traffic. You cannot use the management port for normal traffic that is slated for load
balancing. Instead, the BIG-IP system uses the TMM switch interfaces for that type of
traffic. TMM switch interfaces are those interfaces controlled by the Traffic
Management Microkernel (TMM) service.
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Configuring the management port of a BIG-IP system means assigning an IP address to
the port, supplying a netmask for the IP address, and specifying an IP address for the
BIG-IP system to use as a default route. The IP address that you assign to the
management port must be on a different network than the self IP addresses that you
assign to VLANs. Note that specifying a default route for the management port is only
necessary if you intend to manage the BIG-IP system from a node on a different subnet.
Note: The IP address for the management port must be in IPv4 format.
TMM Switch Ports
Auto MDI/MDIX functionality is retained when you manually configure an interface to
use specific speed and duplex settings. Therefore, you can use either a straight-through
cable or a crossover cable when media settings are forced, and you will be able to
successfully link to either DTE or DCE devices.
The following specifications are for the available Copper Gigabit Ethernet modules and
the platforms that support those modules.
1000Base-T Copper Ethernet Transceiver SFP module specifications



Connector type: RJ45
Maximum operating distance: 100 meters (328 feet)
Cable specifications: Minimum Cat5; Cat5e or Cat6 recommended
There are many available SFP - Fiber Gigabit Ethernet modules for the different BIG-IP
hardware platforms.
A full list can be found at the following link: Link to Online Topic Content
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Objective - 2.04 Explain how to configure remote authentication
and multiple administration roles on the LTM device
2.04 - Explain the relationship between route domains, user roles and
administrative partitions
Link to Online Topic Content
User access relationships
Every User ID configured on the BIG-IP system is tied to either one administrative
partition (i.e. typical user), or all administrative partitions (i.e. administrator). And the
partition assignment defines where that user can do the functions of their role level
(Guest thru Administrator). This means we can control where and what each user can
affect when they are working in the BIG-IP platform by how we define each users role
and partition access.
We also gain further control of user access to resources through route domains. Each
administrative partition is assigned to a route domain. And since the user is tied to the
partition they are as well.
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2.04 - Explain the mapping between remote users and remote role groups
Link to Online Topic Content
Understanding default remote-account authorization
The Authentication screen that you used to specify the type of remote authentication
server also includes some default authorization values (for the Role, Partition Access,
and Terminal Access settings). Therefore, if you do not explicitly configure these
authorization settings for an individual BIG-IP system user account, the BIG-IP system
assigns the default values to that account. This ensures that all remote user accounts
have valid authorization settings assigned to them.
The default values for the Role, Partition Access, and Terminal Access settings are as
follows:
Role--No Access
Partition Access--All
Terminal Access--Disabled
When you use these default values for a user account, the user account appears in the
list of BIG-IP user accounts as Other External Users.
You can change the values that the BIG-IP system automatically uses as the default
values for the Role, Partition Access, and Terminal Access settings.
To change the default authorization properties for remote user accounts, you configure
the Role, Partition Access, and Terminal Access settings on the same Authentication
screen that you used to specify the type of remote authentication server you are using.
Important: For the Other External Users user account, you can modify the Role, Partition
Access, and Terminal Access settings only when your current partition on the BIG-IP system
is set to Common. If you attempt to modify these settings when your current partition is
other than Common, the system displays an error message.
Note: You can sometimes inadvertently affect your own user account or all user
accounts, if the BIG-IP system is configured to perform remote user authentication, and
you or another system administrator changes the default role or partition assigned to all
external user accounts:

If you log on to the BIG-IP system using one of these remotely-authenticated
Administrator accounts, and you or another Administrator user modifies the
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
default role of all external accounts from Administrator to a lesser role, the
system modifies the user role of your own account to the lesser role. However,
the change to your own account does not actually occur until you log off and log
on again to the BIG-IP system, thus allowing you to complete any tasks you
initiated that still require the Administrator role.
Similarly, your user account can be affected if the BIG-IP system is configured to
perform remote user authentication, and the default partition assigned to all
external user accounts is a specific partition. In this case, if you are logged on to
the BIG-IP system through the command line using one of the remotelyauthenticated accounts, and another user who is logged on through the
Configuration utility modifies the default partition for external users, the BIG-IP
system immediately logs you off when you attempt to issue another command.
Important: If a BIG-IP system administrator changes the user role or partition assignment (or
both) for any remote user account, the BIG-IP system logs off all users immediately. (A
remote user account in this case refers to Other External Users.)
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2.04 - Explain the options for partition access and terminal access
Link to Online Topic Content
Partition Access
A user role defines the access level that a user has for each object in the users assigned
partition. An access level refers to the type of task that a user can perform on an object.
Possible access levels are:

Write
Grants full access, that is, the ability to create, modify, enable and disable, and
delete an object.

Update
Grants the ability to modify, enable, and disable an object.

Enable/disable
Grants the ability to enable or disable an object.

Read
Grants the ability to view an object.
Terminal Access
Specifies the level of access to the BIG-IP system command line interface. Possible
values are: Disabled and Advanced shell.
Users with the Administrator or Resource Administrator role assigned to their accounts
can have advanced shell access, that is, permission to use all BIG-IP system command
line utilities, as well as any Linux commands.
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Objective - 2.05 Given a scenario, determine an appropriate high
availability configuration (i.e., failsafe, failover and timers)
2.05 - Compare and contrast network and serial failover
Link to Online Topic Content
Network Failover
Network failover is based on heartbeat detection where the system sends heartbeat
packets over the internal network.
The system uses the primary and secondary failover addresses to send network failover
heartbeat packets. For more information about the BIG-IP mirroring and network
failover transport protocols, refer to the following articles:


SOL9057: Overview of the BIG-IP LTM network failover transport protocol
SOL7225: Overview of the BIG-IP LTM mirroring transport protocol
The BIG-IP system considers the peer down after the Failover.NetTimeoutSec timeout
value is exceeded. The default value of Failover.NetTimeoutSec is three seconds, after
which the standby unit attempts to switch to an active state. The following database
entry represents the default settings for the failover time configuration:
Failover.NetTimeoutSec = 3
Device Service Clustering (DSC) was introduced in BIG-IP 11.0.0 and allows many new
features such as synchronization and failover between two or more devices. Network
failover provides communication between devices for synchronization, failover, and
mirroring and is required for the following deployments:




Sync-Failover device groups containing three or more devices
Active-active configurations between two BIG-IP platforms
BIG-IP VIPRION platforms
BIG-IP Virtual Edition
An active-active pair must communicate over the network to indicate the objects and
resources they service. Otherwise, if network communications fail, the two systems
may attempt to service the same traffic management objects, which could result in
duplicate IP addresses on the network.
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A broken network may cause BIG-IP systems to enter into active-active mode. To avoid
this issue, F5 recommends that you dedicate one interface on each system to perform
only failover communications and, when possible, directly connect these two interfaces
with an Ethernet cable to avoid network problems that could cause the systems to go
into an active-active state.
Important: When you directly connect two BIG-IP systems with an Ethernet cable, do not
change the speed and duplex settings of the interfaces involved in the connection. If you
do, depending on the BIG-IP software version, you may be required to use a crossover cable.
For more information, refer to SOL9787: Auto MDI/MDIX behavior for BIG-IP platforms.
If you configure a BIG-IP high-availability pair to use network failover, and the hardwired
failover cable also connects the two units, hardwired failover always has precedence; if
network failover traffic is compromised, the two units do not fail over because the
hardwired failover cable still connects them.
Hardwired Failover
Hardwired failover is also based on heartbeat detection, where one BIG-IP system
continuously sends voltage to another. If a response does not initiate from one BIG-IP
system, failover to the peer occurs in less than one second. When BIG-IP redundant
devices connect using a hardwired failover cable, the system automatically enables
hardwired failover.
The maximum hardwired cable length is 50 feet. Network failover is an option if the
distance between two BIG-IP systems exceeds the acceptable length for a hardwired
failover cable.
Note: For information about the failover cable wiring pinouts, refer to SOL1426: Pinouts for
the failover cable used with BIG-IP platforms.
Hardwired failover can only successfully be deployed between two physical devices. In
this deployment, hardwired failover can provide faster failover response times than
network failover. However, peer state may be reported incorrectly when using
hardwired failover alone.
Hardwired failover is only a heartbeat and carries no status information.
Communication over the network is necessary for certain features to function properly.
For example, Traffic Management Microkernel (TMM) uses the network to synchronize
packets and flow state updates to peers for connection mirroring. To enable proper
state reporting and mirroring, F5 recommends that you configure network failover in
addition to hardwired failover.
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2.05 - Explain use cases for MAC masquerading
Link to Online Topic Content
MAC Masquerading
Using MAC masquerading will reduce ARP convergence issues within the BIG-IP LAN
environments when a failover event happens.
To optimize the flow of traffic during failover events, you can configure MAC
masquerade addresses for any defined traffic groups on the BIG-IP system. A MAC
masquerade address is a unique, floating MAC address that you create. You can assign
one MAC masquerade address to each traffic group on a BIG-IP device. By assigning a
MAC masquerade address to a traffic group, you associate that address with any floating
IP addresses associated with the traffic group. By configuring a MAC masquerade
address for each traffic group, a single Virtual Local Area Network (VLAN) can potentially
carry traffic and services for multiple traffic groups, with each service having its own
MAC masquerade address.
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2.05 - Determine when it is appropriate to use more than two LTM
devices in a device service cluster
Link to Online Topic Content
Device Service Cluster
The TMOS within the BIG-IP system includes an underlying architecture that makes it
possible for you to create a redundant system configuration, known as device service
clustering (DSC), for multiple BIG-IP devices on a network. This redundant system
architecture provides both synchronization of BIG-IP configuration data and high
availability at user-defined levels of granularity. More specifically, you can configure a
BIG-IP device on a network to:



Synchronize some or all of its configuration data among any number of BIG-IP
devices on a network
Fail over to one of many available devices
Mirror connections to a peer device to prevent interruption in service during
failover
If you have two BIG-IP devices only, you can create either an active/standby or an
active-active configuration. With more than two devices, you can create a configuration
in which multiple devices are active and can fail over to one of many, if necessary.
Device Service Clusters are intended for environments that need to run multiple active
BIG-IP units to handle capacity and still maintain the ability to fail traffic to additional
BIG-IP resources.
By setting up a redundant system configuration, you ensure that BIG-IP configuration
objects are synchronized and can fail over at useful levels of granularity to appropriate
BIG-IP devices on the network. You also ensure that failover from one device to
another, when enabled, occurs seamlessly, with minimal interruption in application
delivery.
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2.05 - Explain the functionality of HA groups
Link to Online Topic Content
HA Groups
The BIG-IP system includes a feature known as fast failover. Fast failover is a feature
that is based on the concept of an HA group. An HA group is a set of trunks, pools, or
clusters (or any combination of these) that you want the BIG-IP system to use to
calculate an overall health score for a device in a redundant system configuration. A
health score is based on the number of members that are currently available for any
trunks, pools, and clusters in the HA group, combined with a weight that you assign to
each trunk, pool, and cluster. The device that has the best overall score at any given
time becomes or remains the active device.
Note: To use the fast failover feature, you must first create a redundant system
configuration. The fast failover feature is designed for a redundant configuration that
contains a maximum of two devices in a device group, with one active traffic group.
Note: Only VIPRION systems can have a cluster as an object in an HA group. For all other
platforms, HA group members consist of pools and trunks only.
An HA group is typically configured to fail over based on trunk health in particular.
Trunk configurations are not synchronized between units, which means that the number
of trunk members on the two units often differs whenever a trunk loses or gains
members. The HA group feature makes it possible for failover to occur based on
changes to trunk health instead of on system or VLAN failure.
Only one HA group can exist on the BIG-IP system. By default, the HA group feature is
disabled.
To summarize, when you configure the HA group, the process of one BIG-IP device
failing over to the other based on HA scores is noticeably faster than if failover occurs
due to a hardware or daemon failure.
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2.05 - Compare and contrast failover unicast and multicast
Link to Online Topic Content
Failover Unicast and Multicast
The unicast failover configuration uses a self-IP address and TMM switch port to
communicate failover packets between each BIG-IP appliance. For appliance platforms,
specifying two unicast addresses should suffice.
For VIPRION platforms, you should enable multicast and retain the default multicast
address that the BIG-IP system provides. The multicast failover entry uses the
management port to communicate failover packets between each VIPRION system. As
an alternative to configuring the multicast failover option, you can define a unicast mesh
using the management port for each VIPRION system.
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Objective - 2.06 Given a scenario, describe the steps necessary to
set up a device group, traffic group and HA group
2.06 - Explain how to set up sync-only and sync-failover device service
cluster
Link to Online Topic Content
Working With Sync-Failover Device Groups
One of the types of device groups that you can create is a Sync-Failover type of device
group. A Sync-Failover device group contains devices that synchronize configuration
data and fail over to one another when a device becomes unavailable. A maximum of
eight devices is supported in a Sync-Failover device group.
A device in a trust domain can belong to one Sync-Failover device group only.
For devices in this type of device group, the BIG-IP system uses both the device group
and the traffic group attributes of a folder to make decisions about which devices to
target for synchronizing the contents of the folder, and which objects to include in
failover.
In the simplest configuration, you can use the BIG-IP Configuration utility to:
1. Create a Sync-Failover device group containing all of local BIG-IP devices.
2. Assign the device group to the root folder as the default device group.
3. Assign the default traffic group, traffic-group-1, to the root folder as the default
traffic group.
The result is that all folders inherit the default device group and the default traffic group
as their device group and traffic group attribute values, causing all BIG-IP configuration
data on a BIG-IP device to be synchronized to all devices in that device group, and the
objects in traffic-group-1 to fail over to another member of the device group when a
device becomes unavailable.
Creating a Sync-Failover device group
This task establishes failover capability between two or more BIG-IP devices. If the
active device in a Sync-Failover device group becomes unavailable, the configuration
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objects fail over to another member of the device group and traffic processing is
unaffected. You can perform this task on any authority device within the local trust
domain.
1. On the Main tab, click Device Management > Device Groups. The Device Groups
screen displays a list of existing device groups.
2. On the Device Group List screen, click Create.
3. Type a name for the device group, select the device group type Sync-Failover,
and type a description for the device group.
4. In the Configuration area of the screen, select a host name from the Available list
for each BIG-IP device that you want to include in the device group. Use the
Move button to move the host name to the Selected list.
The Available list shows any devices that are members of the device's local trust
domain but not currently members of a Sync-Failover device group. A device can
be a member of one Sync-Failover group only.
5. For Network Failover, select the Enabled check box.
6. Click Finished.
You now have a Sync-Failover type of device group containing BIG-IP devices as
members.
Configuring failover settings on a device group
You use this procedure to configure some failover settings for a specific device group.
1. On the Main tab, click Device Management > Device Groups. The Device Groups
screen displays a list of existing device groups.
2. In the Group Name column, click the name of a device group.
3. On the menu bar, click Failover.
4. In the Link Down Time on Failover field, use the default value of 0.0, or specify a
new value.
This setting specifies the amount of time, in seconds, that interfaces for any
VLANs on external devices are down when a traffic group fails over and goes to
the standby state. Specifying a value other than 0.0 for this setting causes other
vendor switches to use the specified time to learn the MAC address of the
newly-active device.
5. Click Save Changes.
Sample Sync-Failover configuration
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You can use a Sync-Failover device group in a variety of ways. This sample configuration
shows two separate Sync-Failover device groups in the local trust domain. Device group
A is a standard active/standby configuration. Only BIG-IP1 normally processes traffic for
application A. This means that BIG-IP1 and BIG-IP2 synchronize their configurations, and
BIG-IP1 fails over to BIG-IP2 if BIG-IP1 becomes unavailable. BIG-IP1 cannot fail over to
BIG-IP3 or BIG-IP4 because those devices are in a separate device group.
Device group B is also a standard active/standby configuration, in which BIG-IP3
normally processes traffic for application B. This means that BIG-IP3 and BIG-IP4
synchronize their configurations, and BIG-IP3 fails over to BIG-IP4 if BIG-IP3 becomes
unavailable. BIG-IP3 cannot fail over to BIG-IP1 or BIG-IP2 because those devices are in
a separate device group.
Example illustration of a Sync-Failover device group
Working with Sync-Only device groups
One of the types of device groups that you can create is a Sync-Only device group. A
Sync-Only device group contains devices that synchronize configuration data with one
another, but their configuration data does not fail over to other members of the device
group. A maximum of 32 devices is supported in a Sync-Only device group.
A device in a trust domain can be a member of more than one Sync-Only device group.
A device can also be a member of both a Sync-Failover group and a Sync-Only group.
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A typical use of a Sync-Only device group is one in which you configure a device to
synchronize the contents of a specific folder to a different device group than to the
device group to which the other folders are synchronized.
Creating a Sync-Only device group
Follow these steps to create a Sync-Only type of device group. You can perform this
task on any BIG-IP device within the local trust domain.
1. On the Main tab, click Device Management > Device Groups. The Device Groups
screen displays a list of existing device groups.
2. On the Device Group List screen, click Create.
3. Type a name for the device group, select the device group type Sync-Only, and
type a description for the device group.
4. Select an IP address and host name from the Available list for each BIG-IP device
that you want to include in the device group. Use the Move button to move the
host name to the Includes list.
The list shows any devices that are members of the device's local trust domain.
5. For Automatic Sync, select the Enabled check box.
6. Click Finished.
You now have a Sync-Only type of device group containing BIG-IP devices as members.
Enabling and disabling Automatic Sync
For Sync-Only device groups, you can choose to either automatically or manually
synchronize configuration data in a device group.
Note: For Sync-Failover device groups, the BIG-IP system supports manual synchronization
only.
You can use the BIG-IP Configuration utility to enable or disable automatic
synchronization. When enabled, this feature causes any BIG-IP device in the device
group to synchronize its configuration data to the other members of the device group
whenever that data changes.
1. On the Main tab, click Device Management > Device Groups. The Device Groups
screen displays a list of existing device groups.
2. In the Group Name column, click the name of the relevant device group.
3. On the menu bar, click ConfigSync.
4. For Automatic Sync, clear or select the Enabled check box.
5. Click Update.
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Sample Sync-Only configuration
The most common reason to use a Sync-Only device group is to synchronize a specific
folder containing policy data that you want to share across all BIG-IP devices in a local
trust domain, while setting up a Sync-Failover device group to fail over the remaining
configuration objects to a subset of devices in the domain. In this configuration, you are
using a Sync-Only device group attribute on the policy folder to override the inherited
Sync-Failover device group attribute. Note that in this configuration, BIG-IP1 and BIGIP2 are members of both the Sync-Only and the Sync-Failover groups.
Sync-Only Device Group
To implement this configuration, follow this process.
1. Create a Sync-Only device group on the local device, adding all devices in the
local trust domain as members.
2. Create a Sync-Failover device group on the local device, adding a subset of
devices as members.
3. On the folder containing the policy data, use tmsh to set the value of the device
group attribute to the name of the Sync-Only device group.
4. On the root folder, retain the default Sync-Failover device group assignment.
This section uses GUI level instructions to explain the setup and configuration of HA
functionalities. You should be very comfortable with how the configuration looks in the
CLI as well through hands-on work in your vLabs.
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2.06 - Explain how to configure HA groups
Link to Online Topic Content
HA Group Configuration
To configure the BIG-IP system so that failover can occur based on an HA score, you
must specify values for the properties of an HA group. The system makes it possible for
you to configure one HA group only; you cannot create additional HA groups. Once you
have configured HA group properties, the BIG-IP system uses that configuration to
calculate an overall HA score for each device in the redundant system configuration.
1. On the Main tab, click System > High Availability.
2. On the menu bar, click HA Group.
3. In the HA Group Properties area of the screen, in the HA Group Name field, type a name
for the HA group.
4. Verify that the Enable check box is selected.
5. In the Active Bonus field, specify an integer the represents the amount by which you
want the system to increase the overall score of the active device. The purpose of the
active bonus is to prevent failover when minor or frequent changes occur to the
configuration of a pool, trunk, or cluster.
6. For the Pools setting, in the Available box, click a pool name and use the Move button to
move the pool name to the Selected box. This populates the table that appears along
the bottom of the screen with information about the pool.
7. For the Trunks setting, in the Available box, click a trunk name and use the Move button
to move the trunk name to the Selected box. This populates the table that appears
along the bottom of the screen with information about the trunk.
8. For the Clusters setting (VIPRION platforms only), in the Available box, click a cluster
name and use the Move button to move the cluster name to the Selected box.
9. In the table displayed along the bottom of the screen, for the Threshold setting, for each
pool or trunk in the HA group, optionally specify an integer for a threshold value.
10. For the Weight setting, for each pool or trunk in the HA group, specify an integer for the
weight. The allowed weight for an HA group object ranges from 10 through 100. This
value is required.
11. Click Create.
You now have an HA group that the BIG-IP system can use to calculate an HA score for
failover. This section uses GUI level instructions to explain the setup and configuration
of HA functionalities. You should be very comfortable with how the configuration looks
in the CLI as well through hands-on work in your vLabs.
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2.06 - Explain how to assign virtual servers to traffic groups
Traffic Group Assignment
When a virtual server is created it will inherit the default traffic group of the
partition/path that it is created in. However there can be more than one traffic group in
a partition.
If you want to move the virtual server object to a different traffic group:
1. On the Main tab, click Local Traffic > Virtual Server > Virtual Address List.
2. Click on the address of the virtual server you wan to modify.
3. In the Traffic Group field change the selection box to the Traffic Group you wish
to use.
4. Click Update.
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Objective - 2.07 Predict the behavior of an LTM device group or
traffic groups in a given failure scenario
2.07 Predict the behavior of an LTM device group or traffic groups in a
given failure scenario
Link to Online Topic Content
Scenario Based Questions
To prepare for scenario based questions the candidate will need to complete hands-on
configuration and testing of the configuration on the LTM. This will allow the candidate
to better understand how different configurations can produce different results. All F5
exams use scenario-based questions that make the candidate apply what they know to a
situation to determine the resulting outcome.
This topic is focused on predicting behaviors during failovers between BIG-IP systems.
Understanding how device groups and traffic groups behave is the key to this topic.
Experience with failing over HA systems will give the candidate the ability to answer the
questions on this topic.
F5 introduced the Device Service Clustering (DSC) architecture in BIG-IP 11.x. DSC
provides the framework for ConfigSync, and other high-availability features, including
the following components:
Device trust and trust domains
Device trust establishes trust relationships between BIG-IP devices through certificatebased authentication. Each device generates a device ID key and Secure Socket Layer
(SSL) certificate upon upgrade or installation. A trust domain is a collection of BIG-IP
devices that trust each other, and can synchronize and fail over their BIG-IP
configuration data, as well as regularly exchange status and failover messages.
When the local BIG-IP device attempts to join a device trust with a remote BIG-IP device,
the following applies:
If the local BIG-IP device is added as a peer authority device, the remote BIG-IP device
presents a certificate signing request (CSR) to the local device, which then signs the CSR
and returns the certificate along with its CA certificate and key.
If the local BIG-IP device is added as a subordinate (non-authority) device, the remote
BIG-IP device presents a CSR to the local device, which then signs the CSR and returns
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the certificate. The CA certificate and key are not presented to the remote BIG-IP
device. The subordinate device is unable to request other devices to join the device
trust.
Device groups
A device group is a collection of BIG-IP devices that reside in the same trust domain and
are configured to securely synchronize their BIG-IP configuration and failover when
needed. Device groups can initiate a ConfigSync operation from the device group
member with the desired configuration change. You can create two types of device
groups:
A Sync-Failover device group contains devices that synchronize configuration data and
support traffic groups for failover purposes.
A Sync-Only device group contains devices that synchronize configuration data, but do
not synchronize failover objects and do not fail over to other members of the device
group.
Traffic groups
A traffic group represents a collection of related configuration objects that are
configured on a BIG-IP device. When a BIG-IP device becomes unavailable, a traffic
group can float to another device in a device group.
Folders
A folder is a container for BIG-IP configuration objects. You can use folders to set up
synchronization and failover of configuration data in a device group. You can sync all
configuration data on a BIG-IP device, or you can sync and fail over objects within a
specific folder only.
Centralized Management Infrastructure (CMI) communication channel
The BIG-IP system uses SSL certificates to establish a trust relationship between devices.
In a device trust, BIG-IP devices can act as certificate signing authorities, peer
authorities, or subordinate non-authorities. When acting as a certificate signing
authority, the BIG-IP device signs x509 certificates for another BIG-IP device that is in
the local trust domain. The BIG-IP device for which a certificate signing authority device
signs its certificate is known as a subordinate non-authority device. The BIG-IP system
uses the following certificates to establish a secure communication channel:
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Objective - 2.08 Determine the effect of LTM features and/or
modules on LTM device performance and/or memory
2.08 - Determine the effect of iRules on performance
Link to Online Topic Content
Effect of iRules on Performance
This is a classic case of “It Depends”. Since iRules are written individually to solve
specific issues or do specific functions necessary for a particular scenario, there is not a
fixed sheet of performance numbers showing how an iRule will impact performance.
iRules do get compiled into byte code, and can run at wire speed, but it really depends
on what you're doing. Many times there is more than one way to write an iRule and one
method may work more efficiently than another.
That said there are ways to see how an iRule is performing by collecting and interpreting
runtime statistics by inserting a timing command into event declarations to see over all
CPU usage when under load. This tool will help you to create an iRule that is performing
the best on your system.
Collecting Statistics
To generate & collect runtime statistics, you can insert the command "timing on" into
your iRule. When you run traffic through your iRule with timing enabled, LTM will keep
track of how many CPU cycles are spent evaluating each iRule event. You can enable
rule timing for the entire iRule, or only for specific events.
To enable timing for the entire iRule, insert the "timing on" command at the top of the
rule before the first "when EVENT_NAME" clause.
With the timing command in place, each time the rule is evaluated, LTM will collect the
timing information for the requested events.
To get a decent average for each of the events, you'll want to run at least a couple
thousand iterations of the iRule under the anticipated production load.
Viewing Statistics
The statistics for your iRule (as measured in CPU cycles) may be viewed at the command
line or console by running
tmsh show ltm rule rule_name all
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The output includes totals for executions, failures & aborts along with minimum,
average & maximum cycles consumed for each event since stats were last cleared.
-------------------------------------------------Ltm::Rule rule_name
-------------------------------------------------Executions
Total
729
Failures
0
Aborts
0
CPU Cycles on Executing
Average
3959
Maximum
53936
Minimum
3693
Evaluating statistics
“Average cycles reported” is the most useful metric of real-world performance,
assuming a large representative load sample was evaluated.
The “maximum cycles reported” is often very large since it includes some one-time and
periodic system overhead. (More on that below.)
Here's a spreadsheet (iRules Runtime Calculator) that will calculate percentage of CPU
load per iteration once you populate it with your clock speed and the statistics gathered
with the "timing" command. (Clock speed can be found by running 'cat /proc/cpuinfo'
at the command line.)
Caveats
Timing is intended to be used only as an optimization/debug tool, and does have a small
impact on performance; so don't leave it turned on indefinitely.
Timing functionality seems to exhibit a 70 - 100 cycle margin of error.
Use average cycles for most analyses. Maximum cycles is not always an accurate
indicator of actual iRule performance, as the very first call a newly edited iRule includes
the cycles consumed for compile-time optimizations, which will be reflected in an
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inflated maximum cycles value. The simple solution to this is to wait until the first time
the rule is hit, then reset the statistics.
However, maximum cycles is also somewhat inflated by OS scheduling overhead
incurred at least once per tick, so the max value is often overstated even if stats are
cleared after compilation.
Link to Online Topic Content
Global Variable Impact
iRules use global variables to make variable data that is created in one context, that is
available to other connections, virtual servers, and Traffic Management Microkernel
(TMM) instances. If a virtual server references an iRule that uses a global variable that is
not Clustered Multiprocessing (CMP) compatible, the virtual server will be ineligible for
CMP processing. In most cases, it is good to retain the benefits of CMP processing when
using iRules. This document expands on the various ways to represent global variable
data, making it available to other connections, other virtual servers, and other TMM
instances.
In many cases, variable data used in an iRule is required to be available only within the
scope of the current connection. The use of Tcl local variables satisfies this
requirement, and does not affect CMP compatibility.
In other cases, variable data must be available globally, that is, outside the context of a
connection. The most common requirement people have is to capture data from one
connection, then to reference that data from subsequent connections that are part of
the same session. This requirement can be further refined to include both multiple
connections traversing the same TMM instance, such as would be seen on a non-CMPenabled system or virtual server, and also multiple related connections on CMP-enabled
virtual servers, which may traverse different TMM instances.
Another common use for global variables is to share data among multiple iRules that run
on the same BIG-IP system. For example, to set and enforce a cumulative concurrent
connection limit, an iRule would need to both set a globally accessible limit value, and
also allow each iRule instance to update a separate globally-accessible counter value.
The use of global variables can force the BIG-IP system to automatically disable CMP
processing, which is known as demotion. Demotion of a virtual server limits processing
of that virtual server to only one CPU core. This can adversely affect performance on
multi-core BIG-IP systems, as only a fraction of the available CPU resources are available
for each demoted virtual server. In addition, CMP demotion can create an internal
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communication bottleneck for virtual servers that are WebAccelerator-enabled or ASMenabled.
The following sections explain each of three popular methods for sharing iRules-derived
data globally, including the CMP compatibility of each method.
Using Tcl global variables
Tcl global variables are not actually global on a CMP-enabled BIG-IP system, since the
global variables are not shared among TMM instances. Tcl global variables are
accessible globally only within the local TMM instance (meaning that each TMM
instance would need to set and update separately its own copy of the variable and the
value of the variable). As a result, the TMM process running on one processor is not
able to access the contents of the same Tcl global variable that was set by a different
TMM process, even if both TMM processes are handling connections for the same
virtual server. Because of this limitation, the use of a Tcl global variable in an iRule
automatically demotes from CMP any virtual server to which it is applied. This avoids
the confusion that would otherwise result from accessing and updating multiple
instances of the same “global” variable. Because the virtual server will be automatically
demoted from CMP, you should restrict the use of Tcl global variables to iRules that will
be applied to virtual servers that do not depend on CMP processing.
Using static global variables
If you must share static data (data that will never be modified by the iRule itself) across
CMP-enabled virtual servers, you can use a static global variable. A static global variable
stores data globally to the entire BIG-IP system, and is set within each TMM instance
each time the iRule is initialized. The value of a static global variable is assumed not to
change unless the iRule is re-initialized. As a result, static global variables must be set
within the RULE_INIT event. Static global variables set within the RULE_INIT event are
propagated to all TMM instances each time the iRule is initialized: when the iRule is
loaded at system startup, when the configuration is re-loaded, or when the iRule is
modified from within the BIG-IP Configuration utility and saved.
Important: While it is possible to use the set command to modify a static global variable
within the iRule and outside of the RULE_INIT event, such modifications will not be
propagated to each TMM instance; they will be visible to only the TMM process on
which the modification was made, resulting in inconsistent values for the static global
variable across TMM instances. As a result, F5 strongly recommends that you do not
update the value of any static global variable within the iRule.
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Using the session table to store global variables
If you must share non-static global data across CMP-enabled virtual servers, you can use
the session table to store and reference the data. Session table data is shared among all
TMM instances. Using the session table imposes considerable operational overhead,
but the preservation of CMP processing for the virtual server typically far outweighs any
such impact.
You can use the table command to manipulate the session table. For details, refer to
the DevCentral article linked in the Supplemental Information section below.
Recommendations
As you can see, there are several different options for using global variables, or the
equivalent functionality, in session tables. Each of these options has advantages and
disadvantages in their use. Typically these decisions are made on performance and ease
of implementation.
In summary:
Tcl global variables
You should restrict the use of Tcl global variables to iRules that will be applied to virtual
servers that do not depend on CMP processing.
Static global variables
The use of static global variables is recommended for sharing static data (data that will
not be updated by any iRule) among TMM instances that are used by CMP-enabled
virtual servers, or for sharing static data among multiple iRules without affecting the
CMP status of any virtual server to which it is applied.
Session table
The use of the session table is recommended for sharing dynamic global variable data
(data that will be updated within the iRule) among CMP-enabled virtual servers.
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2.08 - Determine the effect of RAM cache on performance and memory
Link to Online Topic Content
Effect of RAM Cache on Performance
The largest effect of using the RAM Cache feature on the BIG-IP system is system
memory utilization. There is a finite amount of RAM in every system and using any
amount of that RAM for caching HTTP objects can impact performance and even limit
provisioning additional licensing options.
RAM Cache
A RAM Cache is a cache of HTTP objects stored in the BIG-IP system’s RAM that are
reused by subsequent connections to reduce the amount of load on the back-end
servers.
When to use the RAM Cache
The RAM Cache feature provides the ability to reduce the traffic load to back-end
servers. This ability is useful if an object on a site is under high demand, if the site has a
large quantity of static content, or if the objects on the site are compressed.

High demand objects
This feature is useful if a site has periods of high demand for specific content.
With RAM Cache configured, the content server only has to serve the content to
the BIG-IP system once per expiration period.

Static content
This feature is also useful if a site consists of a large quantity of static content
such as CSS, javascript, or images and logos.

Content compression
For compressible data, the RAM Cache can store data for clients that can accept
compressed data. When used in conjunction with the compression feature on
the BIG-IP system, the RAM Cache takes stress off of the BIG-IP system and the
content servers.
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Items you can cache
The RAM Cache feature is fully compliant with the cache specifications described in RFC
2616, Hypertext Transfer Protocol -- HTTP/1.1. This means you can configure RAM
Cache to cache the following content types:




200, 203, 206, 300, 301, and 410 responses
Responses to GET methods by default.
Other HTTP methods for URIs specified in the URI Include list or specified in an
iRule.
Content based on the User-Agent and Accept-Encoding values. The RAM Cache
holds different content for Vary headers.
The items that the RAM Cache does not cache are:


Private data specified by cache control headers
By default, the RAM Cache does not cache HEAD, PUT, DELETE, TRACE, and
CONNECT methods.
Understanding the RAM Cache mechanism
The default RAM Cache configuration caches only the HTTP GET methods. You can use
the RAM Cache to cache both the GET and other methods, including non-HTTP methods,
by specifying a URI in the URI Include list or writing an iRule.
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2.08 - Determine the effect of compression on performance
Link to Online Topic Content
Effect of Compression on Performance
The function of data compression is highly CPU intensive. The largest effect of using the
RAM Cache feature on the BIG-IP system is system memory utilization. There is a finite
amount of RAM in every system and using any amount of that RAM for caching HTTP
objects can impact performance and even limit provisioning additional licensing options.
HTTP Compression
An optional feature is the BIG-IP systems ability to off-load HTTP compression tasks
from the target server. All of the tasks needed to configure HTTP compression in Local
Traffic Manager, as well as the compression software itself, are centralized on the BIG-IP
system.
gzip compression levels
A gzip compression level defines the extent to which data is compressed, as well as the
compression rate. You can set the gzip level in the range of 1 through 9. The higher the
gzip level, the better the quality of the compression, and therefore the more resources
the system must use to reach that specified quality. Setting a gzip level yields these
results:


A lower number causes data to be less compressed but at a higher performance
rate. Thus, a value of 1 causes the least compression but the fastest
performance.
A higher number causes data to be more compressed but at a slower
performance rate. Thus, a value of 9 (the highest possible value) causes the
most compression, but the slowest performance.
Warning: Selecting any value other than 1 - Least Compression (Fastest) can degrade
system performance.
For example, you might set the gzip compression level to 9 if you are utilizing Local
Traffic Manager cache feature to store response data. The reason for this is that the
stored data in the cache is continually re-used in responses, and therefore you want the
quality of the compression of that data to be very high.
As the traffic flow on the BIG-IP system increases, the system automatically decreases
the compression quality from the gzip compression level that you set in the profile.
When the gzip compression level decreases to the point where the hardware
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compression provider is capable of providing the specified compression level, the
system uses the hardware compression providers rather than the software compression
providers to compress the HTTP server responses.
Tip: You can change the way that Local Traffic Manager uses gzip levels to compress
data by configuring the compression strategy. The compression strategy determines the
particular compression provider (hardware or software) that the system uses for HTTP
responses. The available strategies are: Speed (the default strategy), Size, Ratio, and
Adaptive.
Memory levels for gzip compression
You can define the number of kilobytes of memory that Local Traffic Manager uses to
compress data when using the gzip or deflate compression method. The memory level
is a power-of-2 integer, in bytes, ranging from 1 to 256.
Generally, a higher value causes Local Traffic Manager to use more memory, but results
in a faster and higher compression ratio. Conversely, a lower value causes Local Traffic
Manager to use less memory, but results in a slower and lower compression ratio.
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2.08 - Determine the effect of modules on performance and memory
Link to Online Topic Content
Effect of Modules On Performance
Enabling additional software on any F5 hardware platform will increase the utilization of
the hardware resources of the unit. As you provision the software modules in TMOS the
Resource Provisioning screen will show the administrator how much CPU, Disk and
Memory is being used by each module. And if provisioning an additional module
requires more resources than are available on the system, the system will not allow the
provisioning of the module.
Resource Provisioning is a management feature to help support the installation and
configuration of many modules available with BIG-IP. Provisioning gives you some
control over the resources, both CPU and RAM, which are allocated to each licensed
module. You may want, for example, to minimize the resources available to GTM on a
system licensed for LTM and GTM. Since all models have some reliance on both
management (Linux) and local traffic features, they will always be provisioned. Other
modules must be manually provisioned. When you provision the modules, you can
choose between four levels of resources. A fifth level may be allowed on certain
modules. Dedicated, Nominal, Minimum and None are available for all modules and Lite
is a fifth level available for trials only.
You can manage the provisioning of system memory, disk space, and CPU usage among
licensed modules on the BIG-IP system.
There are five available resource allocation settings for modules.
None/Disabled
Specifies that a module is not provisioned. A module that is not provisioned
does not run.
Dedicated
Specifies that the system allocates all CPU, memory, and disk resources to one
module. When you select this option, the system sets all other modules to None
(Disabled).
Nominal
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Specifies that, when first enabled, a module gets the least amount of resources
required. Then, after all modules are enabled, the module gets additional
resources from the portion of remaining resources.
Minimum
Specifies that when the module is enabled, it gets the least amount of resources
required. No additional resources are ever allocated to the module.
Lite
Lite is available for selected modules granting limited features for trials.
Provisioning licensed modules in BIG-IP through 11.2.1
1.
2.
3.
4.
Log in to the BIG-IP Configuration utility.
Click System.
Click Resource Provisioning.
In the Resource Provisioning (Licensed Modules) section, from the drop-down
menu, select Minimum or Nominal for each licensed module.
5. After making the necessary provisioning changes, click System, click
Configuration, click Device, and then click the Reboot button to restart the
system.
6. When prompted, click OK to confirm the restart operation.
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Objective - 2.09 Determine the effect of traffic flow on LTM
device performance and/or utilization
2.09 - Explain how to use traffic groups to maximize capacity
Link to Online Topic Content
Traffic Groups
A traffic group is a collection of related configuration objects that run on a BIG-IP device.
Together, these objects process a particular type of traffic on that device. When a BIGIP device becomes unavailable, a traffic group floats (that is, fails over) to another
device in a device group to ensure that application traffic continues to be processed
with little to no interruption in service. In general, a traffic group ensures that when a
device becomes unavailable, all of the failover objects in the traffic group fail over to
any one of the devices in the device group, based on the number of active traffic groups
on each device.
A traffic group is initially active on the device on which you create it, until the traffic
group fails over to another device. For example, if you initially create three traffic
groups on Device A, these traffic groups remain active on Device A until one or more
traffic groups fail over to another device. If you want to balance the traffic group load
among all devices in the device group, you can intentionally cause a traffic group to fail
over to another device. You do this using the Force to Standby option of the
Configuration utility.
Important: Although a specific traffic group can be active on only one device in a device
group, the traffic group actually resides and is in a standby state on all other device group
members, due to configuration synchronization.
Only certain types of configuration objects can belong to a traffic group. Examples of
traffic group objects are self IP addresses and virtual IP addresses.
An example of a set of objects in a traffic group is an iApps application service. If a
device with this traffic group is a member of a device group, and the device becomes
unavailable, the traffic group floats to another member of the device group, and that
member becomes the device that processes the application traffic.
When a traffic group fails over to another device in the device group, the device that the
system selects is normally the device with the least number of active traffic groups.
When you initially create the traffic group on a device, however, you specify the device
in the group that you prefer that traffic group to run on in the event that the available
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devices have an equal number of active traffic groups (that is, no device has fewer
active traffic groups than another). Note that, in general, the system considers the most
available device in a device group to be the device that contains the fewest active traffic
groups at any given time.
Maximizing Capacity
I could not find any specific documentation on maximizing capacity with Traffic Groups
and the resource guide does not have any references to content.
I believe that they are trying to emphasize the fact that with the creations of traffic
groups you can move the servicing of the traffic group resources from one device to
another and thus balance loads or maximize capacity across devices.
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Objective - 2.10 Determine the effect of virtual server settings
on LTM device performance and/or utilization
2.10 - Determine the effect of connection mirroring on performance
Link to Online Topic Content
Connection Mirroring Performance Implications
The connection and persistence mirroring feature allows you to configure a BIG-IP
system to duplicate connection and persistence information to the standby unit of a
redundant pair. This setting provides higher reliability, but might affect system
performance.
The BIG-IP device service clustering (DSC) architecture allows you to create a redundant
system configuration for multiple BIG-IP devices on a network. System redundancy
includes the ability to mirror connection and persistence information to a peer device to
prevent interruption in service during failover. Traffic Management Microkernel (TMM)
manages the state mirroring mechanism, and connection and persistence data is
synchronized to the standby unit with every packet or flow state update. The standby
unit decapsulates the packets and adds them to the connection table.
This feature can add CPU overhead to the system and can also cause network
congestion depending on the system configuration.
Recommendations
When configuring mirroring on the BIG-IP system, F5 recommends that you consider the
following factors:
Note: Only FastL4 and SNAT connections are re-mirrored after failback.

Enable connection and persistence mirroring when a BIG-IP failover would cause
the user's session to be lost or significantly disrupted
For example, where long-term connections, such as FTP and Telnet, are good
candidates for mirroring, mirroring short-term connections, such as HTTP and
UDP, is not recommended as this causes a decrease in system performance. In
addition, mirroring HTTP and UDP connections is typically not necessary, as
those protocols allow for failure of individual requests without loss of the entire
session.
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
Configure a dedicated VLAN and dedicated interfaces to process mirroring traffic
The TMM process manages the BIG-IP LTM state mirroring mechanism, and
connection data is synchronized to the standby unit with every packet or flow
state update. In some mirroring configurations, this behavior may generate a
significant amount of traffic. Using a shared VLAN and shared interfaces for both
mirroring and production traffic reduces the overall link capacity for either type
of traffic. Due to high traffic volumes, production traffic and mirroring traffic
may interfere, potentially causing latency in mirrored connections or
interrupting the network mirror connection between the two BIG-IP devices. If
the network mirror connection is interrupted, it can cause loss of mirror
information and interfere with the ability of the peer device to take over
connections in the event of a failover.

Directly cable network mirroring interfaces
You can directly cable network mirroring interfaces on the BIG-IP systems in the
failover pair, and F5 highly recommends that you do this when configuring a
dedicated VLAN for mirroring. Configuring the pair in this way removes the need
to allocate additional ports on surrounding switches, and removes the possibility
of switch failure and switch-induced latency. Interfaces used for mirroring
should be dedicated to the mirroring VLAN. Tagged interfaces shared with other
VLANs could become saturated by traffic on other VLANs.

Configure both primary and secondary mirroring addresses
This would allow an alternate mirroring path and ensure reliable mirroring in the
event of equipment or cable failure.
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Objective - 2.11 Describe how to deploy vCMP guests and how
the resources are distributed
Link to Online Topic Content
VCMP
Virtual Clustered Multiprocessing (vCMP) is a BIG-IP feature that allows you to run
multiple instances of the BIG-IP software (vCMP guests) on a single hardware platform.
Typically, the initial BIG-IP configuration involves setting a host name, configuring
Virtual Local Area Networks (VLANs) and self IPs, setting up High Availability (HA), and
then configuring traffic objects such as pools, virtual servers, secure network address
translations (SNATs), and other options made available by various BIG-IP modules. The
vCMP feature changes the initial configuration model with the vCMP host and vCMP
guest relationship, and understanding where to configure these options will ensure that
the vCMP systems function properly. The following statements provide a brief
description of the vCMP host and vCMP guest:


The vCMP host is the system-wide hypervisor that makes it possible for you to
create, view, and manage all vCMP guests on the system. A vCMP host allocates
system resources to vCMP guests as needed.
A vCMP guest is an object that you create on the vCMP host system for the
purpose of running one or more BIG-IP modules. A vCMP guest consists of a
Traffic Management Operating System (TMOS) instance, plus one or more BIG-IP
modules. Each vCMP guest has its own share of hardware resources that the
vCMP host allocates to it, effectively making each vCMP guest function like a
separate BIG-IP device.
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2.11 - Identify platforms that support vCMP
Link to Online Topic Content
Version 11.2 Hardware Platforms for vCMP
This list of supported hardware for vCMP was a short list in TMOS version 11.2, which
this exam is currently based on.
The following is a list of available vCMP hardware for TMOS version 11.2:



VIPRION 2400 with B2100 series blades
VIPRION 4400(J100) with B4200 series blades
VIPRION 4400(J100)/4480(J102) with B4300 series blades
Note: F5 introduced support for the VIPRION B4300 blade in the 4400(J100) or 4480(J102) 4slot chassis in BIG-IP 11.2.0. Support for the VIPRION B4300 blade in the 4800(S100) 8-slot
chassis was not available until BIG-IP 11.4.0.
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2.11 - Identify the limitations of vCMP
Link to Online Topic Content
Limitations of vCMP
When configuring the vCMP feature, you should consider the following factors:


Once you provision the vCMP feature, you cannot provision any BIG-IP modules,
such as BIG-IP LTM, on the vCMP host. Moreover, if you have already
provisioned any BIG-IP modules on the BIG-IP system before you provision the
vCMP feature, those modules are de-provisioned when you provision the vCMP
feature. This situation, in turn, interrupts any application traffic that the system
is currently processing.
When you are logged in to the vCMP host, do not attempt to configure BIG-IP
module features, such as virtual servers, pools, and profiles. You should use the
vCMP host only to create and manage vCMP guests and to perform Layer 2 (L2)
network configuration. If you attempt to configure BIG-IP modules while you are
logged in to the vCMP host, the system can produce unexpected results. Always
log in to the relevant vCMP guest before you configure BIG-IP module features.
Redundancy considerations:


The self IP addresses that you specify per vCMP guest for configuration
synchronization (ConfigSync) and failover should be the self IP addresses
configured on the vCMP guest (not the vCMP host). Similarly, the
management IP address that you specify per vCMP guest for device trust and
failover should be the cluster IP address of the vCMP guest.
For Sync-Failover device groups, each device group member must run on a
chassis separate from the other members. The maximum supported size of a
Sync-Failover device group is eight members.
Important: Device group members should be vCMP guests, not vCMP hosts. Configuring
redundancy between or among vCMP hosts could produce unexpected results.


When you initially log in to the system to configure a vCMP guest, you access the
vCMP host using its management IP address.
When performing resource-intensive actions, such as upgrading software or
installing hotfixes for a vCMP guest, it is important to maintain resources on the
vCMP host system.
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2.11 - Describe the effect of licensing and/or provisioning on the vCMP
host and vCMP guest
Link to Online Topic Content
BIG-IP license considerations for vCMP
If vCMP was a purchased licensed component on the BIG-IP system, then you can
provision the vCMP feature and create guests with one or more BIG-IP system modules
provisioned. For example, if you purchased a BIG-IP 5200v licensed with LTM, GTM,
ASM and vCMP you can provision vCMP on the BIG-IP 5200v and each guest has access
to the LTM, GTM and ASM license.
Note the following considerations:




Each guest inherits the license of the vCMP host.
The host license must include all BIG-IP modules that are to be provisioned
across all guest instances. Examples of BIG-IP modules are BIG-IP Local Traffic
Manager and BIG-IP Global Traffic Manager.
The license allows you to deploy the maximum number of guests that the
platform allows.
If the license includes the appliance mode feature, you cannot enable appliance
mode for individual guests; when licensed, appliance mode applies to all guests
and cannot be disabled.
You activate the BIG-IP system license when you initially set up the system.
vCMP provisioning
To enable the vCMP feature, you perform two levels of provisioning. First, you provision
the vCMP feature as a whole. When you do this, the BIG-IP system, by default,
dedicates most of the disk space to running the vCMP feature, and in the process,
creates the host portion of the vCMP system. Second, once you have configured the
host to create the guests, each guest administrator logs in to the relevant guest and
provisions the required BIG-IP modules. In this way, each guest can run a different
combination of modules. For example, one guest can run LTM only, while a second
guest can run LTM and ASM.
Important: Once you provision the vCMP feature, you cannot provision any BIG-IP modules,
such as BIG-IP LTM, on the vCMP host. Moreover, if any BIG-IP modules are already
provisioned on the system before you provision the vCMP feature, those modules are deprovisioned when you provision the vCMP feature. This, in turn, interrupts any application
traffic currently being processed.
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Note: The reserved disk space protects against any possible resizing of the file system.
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2.11 - Describe how to deploy vCMP guests
Link to Online Topic Content
Creating a vCMP guest
To create a vCMP guest, you need a VIPRION chassis system configured with a floating
cluster management IP address, some base network objects such as trunks and VLANs,
and you must license and provision the system to run the vCMP feature.
A guest can run on one available slot or all available slots of a chassis.
This illustration shows three guests running on a BIG-IP system. Guest 1 runs on a single
slot only. Guest 2 and Guest 3 each run on all available slots.
You create a vCMP guest when you want to configure and run one or more BIG-IP
modules as though the modules were running together on their own BIG-IP device. For
example, you can create a guest that runs BIG-IP Local Traffic Manager and BIG-IP
Global Traffic Manager.
Note: This procedure creates a guest in Bridged mode.
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Note: When creating a guest, if you see an error message such as “Insufficient disk space on
/shared/vmdisks. Need 24354M additional space.”, you must delete existing unattached
virtual disks until you have freed up that amount of disk space.
1. Use a browser to log in to the VIPRION chassis's management IP address. This
logs you in to the floating IP address for the cluster.
2. On the Main tab, click vCMP > Guest List.
3. Click Create.
4. From the Properties list, select Advanced.
5. In the Name field, type a name for the guest.
6. In the Host Name field, type the host name of the BIG-IP system. Assign a fullyqualified domain name (FQDN). If you assign a name that is not an FQDN, the
system might display an error message. If you leave this field blank, the system
assigns the name localhost.localdomain.
7. From the Number of Slots list, select either Single Slot or All Slots. This causes
the guest to reside on one slot or to span all slots. Note that once you configure
a guest to span all slots, you cannot change this value later to Single Slot, unless
you first change the state of the guest to Configured. Also note that if you
decide to reconfigure an all slot guest to a single slot guest, you cannot specify
on which available single slot the guest will reside.
8. From the Management Network list, select Bridged.
9. For the Cluster IP Address setting, fill in the required information:
10. In the IP Address field, type a unique management IP address that you want to
assign to the guest. You use this IP address to access the guest when you want
to manage a module running within the guest.
11. In the Network Mask field, type the network mask for the cluster IP address.
12. In the Management Route field, type a gateway address for the cluster IP
address.
13. From the Initial Image list, select an ISO image file for installing TMOS software
and the BIG-IP license onto the guest's virtual disk. The license associated with
the selected image provides access to the correct BIG-IP modules.
14. In the Virtual Disk list, retain the default value of None. The BIG-IP system
creates a virtual disk with a default name (the guest name plus the string .img,
such as guestA.img). Note that if an unattached virtual disk file with that default
name already exists, the system displays a message, and you must manually
attach the virtual disk. You can do this using the tmsh command line interface,
or use the Configuration utility to view and select from a list of available
unattached virtual disks.
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15. For the VLAN List setting, select both an internal and an external VLAN name
from the Available list, and use the Move button to move the VLAN names to the
Selected list.
16. From the Requested State list, select Provisioned. This allocates all necessary
resources to the guest, such as CPU cores, virtual disk, and so on.
17. Click Finish.
After clicking Finished, wait while the system installs the selected ISO image onto the
guest's virtual disk. When this process is complete, you can deploy the guest.
Note: You can also skip the Provisioned state and instead go straight to the Deployed state if
you are confident of your guest configuration. Provisioning first and then deploying makes
it more straightforward to make changes to the slots to which your guests are allocated if
you find you need to make changes.
Setting a vCMP guest to the Deployed state
Until you deploy a vCMP guest, your vCMP VIPRION has no medium for provisioning and
running the BIG-IP modules that you can use to process traffic.
1. Ensure that you are still logged in to the vCMP host using the BIG-IP system's
cluster IP address.
2. On the Main tab, click vCMP > Guest List.
3. In the Name column, click the name of the vCMP guest that you want to deploy.
4. From the Requested State list, select either Provisioned or Deployed.
5. Click Update.
After moving a vCMP guest to the Deployed state, wait while the guest boots and
becomes accessible. Then, you can log into the vCMP guest to provision specific BIG-IP
modules.
Provisioning a BIG-IP module within a guest
Before you can access a guest to provision BIG-IP modules, the vCMP guest must be in
the Deployed state.
You determine which BIG-IP modules run within a guest by provisioning the modules.
For example, if you want guestA to run LTM and GTM, log into guestA and provision it
with LTM and GTM. If you want guestB to run LTM and ASM, log into guestB and
provision it with BIG-IP LTM and BIG-IP ASM. Bear in mind that guests inherit the
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licenses of the vCMP host on which they were created, so any BIG-IP modules that you
want to provision on a guest must be included in the license you installed with the vCMP
host.
Note: This procedure applies to guests in Bridged mode only. Guests in isolated mode can
be accessed only using vconsole and tmsh.
1. Use a browser and the management IP address that you configured for the guest
to log in to the guest. If the system prompts you to run the Setup Utility, do not.
Instead, complete this task to produce an initial configuration better suited for a
vCMP guest. The BIG-IP Configuration utility opens so that you can configure the
guest.
2. On the Main tab, click System > Resource Provisioning.
3. In the Resource Provisioning (Licensed Modules) area, from the Local Traffic
(LTM) list, select Minimal, Nominal, or Dedicated, depending on your needs.
4. Click Update.
After provisioning the module from within the guest, create self IP addresses and assign
a vCMP host VLAN to each one. The vCMP host VLANs that you assign to these self IP
addresses are the VLANs you created before creating the guest.
Creating self IP addresses for VLANs
You need at least one VLAN or VLAN group configured before you create a self IP
address.
Self IP addresses enable the BIG-IP system, and other devices on the network, to route
application traffic through the associated VLAN or VLAN group. Repeat the steps in this
task for each VLAN.
1. On the Main tab, click Network > Self IPs. The Self IPs screen opens.
2. Click Create. The New Self IP screen opens.
3. In the Name field, type a unique name that readily identifies the VLAN to which
it will associate for the self IP. Name the self IP for the internal VLAN Internal,
name the external VLAN External, and name the HA VLAN HA.
4. In the IP Address field, type an IP address. This IP address must be within the
address space that corresponds to the VLAN for which it is created (Internal,
External or HA). The system accepts IP addresses in both the IPv4 and IPv6
formats.
5. In the Netmask field, type the network mask for the specified IP address.
6. From the VLAN/Tunnel list, select the VLAN to associate with this self IP address:
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
For the internal network, select the VLAN that is associated with an internal
interface or trunk.
 For the external network, select the VLAN that is associated with an external
interface or trunk.
 For the HA network, select the VLAN that is associated with an internal
interface or trunk.
7. From the Port Lockdown list, select Allow Default.
8. Repeat the last 4 steps, but this time specify an address from your external
network in step 4 and select the VLAN named external in step 6.
9. Repeat steps 3 through 7 one more time, but this time specify an address on
your internal network in step 4 and select the VLAN named HA in step 6.
10. Click Finished. The screen refreshes, and displays the new self IP address in the
list.
The BIG-IP system can send and receive traffic through the specified VLAN or VLAN
group.
Overview: Verifying initial vCMP configuration
Verifying your vCMP configuration confirms that the setup performed up to this point is
functioning properly. Once you establish that the vCMP configuration is correct, you
will likely need to create a profile, pools, and virtual server that are tailored to your
network topology before your guest can begin processing LTM traffic.
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2.11 - Explain how resources are assigned to vCMP guests (e.g., SSL,
memory, CPU, disk)
Link to Online Topic Content
The vCMP host (hypervisor) allocates hardware resources to each BIG-IP vCMP guest
instance.
As you create the vCMP Guest you define the number of slots, which inherently defines
the CPU and memory of the guest. You also define the size of the virtual disk. On
systems that include SSL and compression hardware processors, the vCMP feature
shares these hardware resources among all guests on the system.
About CPU allocation
The following table lists the possible combinations of vCPU and memory allocation for a
vCMP guest on various platforms:
Platfor
m
VIPRION
B2100
Blade
VIPRION
B4200
Blade
VIPRION
B4300
Blade
Available
vCPU per
slot/applian
ce
Possible
vCPU
allocation
per guest
per
slot/applian
ce
Approximate
memory allocated
per guest,
per slot/appliance
based on vCPU
allocation (GB)
Maximum
number of
guests per
slot/applian
ce
8
2, 4, 8
3 - 13
4
8
2, 4
3-6
4
24
2, 4, 6, 12
3 - 21
6
For single-slot guests, when the system allocates CPU cores to a guest, the system
determines the best slot for the guest to run on. The system selects the slot with the
most unallocated CPU cores. For all-slot guests, the system allocates CPU cores from
every available slot.
GUEST
TYPE
Single slot
All slot
CPU CORE ALLOCATION
The system allocates one or more CPU cores to the guest.
The system allocates two CPU cores from each available slot. For
example, if three slots are available, the system allocates two CPU cores
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from each slot, totaling six CPU cores for that guest. The maximum
number of CPU cores that the system can allocate to a guest is eight.
The number of CPU cores that the BIG-IP system assigns to each guest depends on
whether you configure the guest to run on a single slot or on all available slots of the
system:
The BIG-IP system uses a sequential pattern to determine the chassis slot and CPU cores
to which single-slot guests deploy. You control to which slot your guest migrates by
knowing this pattern and making sure that the slot to which you want the guest to
deploy is the next open resource. You open a slot by disabling its guests; you fill a slot
by deploying a temporary guest as placeholder. The table lists the order in which cores
and slots are allocated to deploying guests.
SLOT
#
CPU CORES
0 AND 1
CPU CORES
2 AND 3
CPU CORES
4 AND 5
CPU CORES 6
AND 7
Slot 1
Slot 2
Slot 3
Slot 4
Fills first
Fills second
Fills third
Fills fourth
Fills fifth
Fills sixth
Fills seventh
Fills eighth
Fills ninth
Fills tenth
Fills eleventh
Fills twelfth
Fills thirteenth
Fills fourteenth
Fills fifteenth
Fills sixteenth
About physical memory allocation
The BIG-IP system allocates a portion of the total system memory to each guest.
About virtual disks allocation
A virtual disk is a portion of the total disk space on the BIG-IP system that the system
allocates to a vCMP guest. The system allocates one virtual disk to each slot on which
the guest resides. Although each virtual disk for a guest has a fixed, maximum size limit,
the actual size of a virtual disk is the amount of space that the guest actually uses on
that slot.
The maximum size limit for a guest is 100GB, and the typical footprint of a new guest
(when viewed from the host) is around 5GB.
You cannot explicitly create virtual disks; instead, the BIG-IP system creates virtual disks
whenever you set the state of a guest to Provisioned and the guest does not already
have an attached virtual disk.
About hardware processors allocation
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On systems that include SSL and compression hardware processors, the vCMP feature
shares these hardware resources among all guests on the system.
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Objective - 2.12 Determine the appropriate LTM device security
configuration to protect against a security threat
2.12 - Explain the implications of SNAT and NAT on network promiscuity
In a typical network, a host’s network adapter only receives frames that are meant for it.
If the Host’s network adapter supports promiscuous mode, then placing it in
promiscuous mode will allow it to receive all frames passed on the switch that are
allowed under the VLAN policy for the associated port group. This can be useful for
intrusion detection monitoring or if a sniffer needs to analyze all traffic on the network
segment.
When the BIG-IP platform performs SNAT or NAT functions to the network traffic that is
traversing the system it rewrites the destination IP or source IP address of the traffic
depending on the function performed. This can make troubleshooting captures of
network traffic difficult since with SNAT all traffic seems to have a source IP address of
the BIG-IP system, or with NAT the destination IP address is not the same on each side
of the communications of the BIG-IP.
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2.12 - Explain the implications of forwarding virtual servers on the
environment security
Link to Online Topic Content
Forwarding Virtual Servers
There are two different types of forwarding virtual server, the Layer2 forwarding and IP
forwarding.
An IP forwarding virtual server accepts traffic that matches the virtual server address
and forwards it to the destination IP address that is specified in the request rather than
load balancing the traffic to a pool. Address translation is disabled when you create an
IP forwarding virtual server, leaving the destination address in the packet unchanged.
When creating an IP forwarding virtual server, as with all virtual servers, you can create
either a host IP forwarding virtual server, which forwards traffic for a single host
address, or a network IP forwarding virtual server, which forwards traffic for a subnet.
Layer 2 (L2) forwarding virtual servers are similar to IP forwarding virtual servers
because they do not have pool members to load balance. Therefore, when the BIG-IP
LTM system evaluates the packet for processing, the system looks only at the
destination IP address.
When creating an L2 forwarding virtual server, it is not possible to specify the
destination of the packet by associating a pool with the virtual server. The BIG-IP LTM
system will forward packets based on the destination L2 Media Access Control (MAC)
address and refer to the forwarding MAC address table.
Forwarding Virtual Servers Security Concerns
Since the forwarding virtual server is not processing traffic to a specific pool resource
traffic can be destined for any IP address in the subnet that the BIG-IP system is listening
on. This may allow traffic to systems that you did not intend to pass.
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2.12 - Describe how to disable services
Link to Online Topic Content
The Big-IP platform is a default deny network platform. You have to configure the BIGIP to listen for traffic whether that is for management or for production traffic. Some
listeners need to be built to pass more than one type of traffic. And many times the
configuration will allow either one port or all ports. If you want to restrict it to a short
list of ports, an iRule can be used that will allow the selective list of ports.
Simply sending a TCP reset to a port scan can tell an intruder a lot about your
environment. By default, the TM.RejectUnmatched BigDB variable is set to true, and
the BIG-IP system sends a TCP RST packet in response to a non-SYN packet that matches
a virtual server address and port or self IP address and port, but does not match an
established connection. The BIG-IP system also sends a TCP RST packet in response to a
packet that matches a virtual server address, or self IP address, but specifies an invalid
port. The TCP RST packet is sent on the client side of the connection, and the source IP
address of the reset is the relevant BIG-IP LTM object address or self IP address for
which the packet was destined. If TM.RejectUnmatched is set to false, the system
silently drops unmatched packets.
Disabling Services On FVS
When you configure a forwarding virtual server you can set the listening port to a single
specific port or all ports. Typically when you are forwarding traffic you will do all ports
so all traffic passes, but you can restrict it to only a certain type.
Creating an IP forwarding virtual server
1.
2.
3.
4.
5.
6.
Log in to the Configuration utility.
Navigate to Local Traffic > Virtual Servers.
Click Create.
Enter a Name for the virtual server.
From the Type menu, select Forwarding (IP).
If the destination is a single host, select Host, or if the destination is a network,
select Network.
7. Enter the IP address for the virtual server (enter a Netmask if the destination is a
network).
8. Enter a Service Port number, or Select a service from the adjacent menu (type an
asterisk character to match all ports).
9. Click Finished.
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2.12 - Describe how to disable ARP
Link to Online Topic Content
Address Resolution Protocol on the BIG-IP system
The BIG-IP system is a multi-layer network device, and as such, needs to perform routing
functions. To do this, the BIG-IP system must be able to find destination MAC addresses
on the network, based on known IP addresses. The way that the BIG-IP system does this
is by supporting Address Resolution Protocol (ARP), an industry-standard Layer 3
protocol. Settings for ARP behaviors can be found on the Main tab, click Network > ARP
> Options. You can also see and manage the dynamic and static ARP entries in ARP
cache from the console or the GUI.
Link to Online Topic Content
Disabling ARP For A Virtual Server’s Address
If you want to control how the BIG-IP handles ARP for a virtual server you can make a
change to the configuration of the virtual address of the virtual server.
What is a virtual address?
A virtual address is the IP address with which you associate a virtual server. For
example, if a virtual server’s IP address and service are 10.10.10.2:80, then the IP
address 10.10.10.2 is a virtual address.
You can create a many-to-one relationship between virtual servers and a virtual address.
For example, you can create the three virtual servers 10.10.10.2:80, 10.10.10.2:443, and
10.10.10.2:161 for the same virtual address, 10.10.10.2.
You can enable and disable a virtual address. When you disable a virtual address, none
of the virtual servers associated with that address can receive incoming network traffic.
A virtual address is created indirectly when you create a virtual server. When this
happens, Local Traffic Manager internally associates the virtual address with a MAC
address. This in turn causes the BIG-IP system to respond to Address Resolution
Protocol (ARP) requests for the virtual address, and to send gratuitous ARP requests and
responses with respect to the virtual address. As an option, you can disable ARP activity
for virtual addresses, in the rare case that ARP activity affects system performance. This
most likely occurs only when you have a large number of virtual addresses defined on
the system.
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2.12 - Explain how to set up logging for security events on the LTM device
Link to Online Topic Content
BIG-IP Local Traffic Manager helps protect against network DoS and DDoS threats.
When using LTM, you can protect against network DoS attacks and increase end-user
application performance with accurate triggers and controls. In BIG-IP LTM, there are a
couple of changes you can make in tightening the configuration and monitoring
messages to ensure the LTM helps protect against DoS and DDoS attacks.
1. Lower the default TCP connection timeouts in the TCP profile.
2. Lower the Reaper percents from low 85 / high 95 to low 75 / high 90.
a. This means fewer connections are held open, but means the LTM will be
more aggressive cleaning out idle connections during a TCP connection flood.
3. Analyze the typical and maximum HTTP header size, including cookies that should
legitimately be seen.
a. The default maximum on LTM is 32k.
b. This should be lowered if your average is 4k and max possible is 8k.
c. In this example, setting the max header size to 16 should adequately ensure
no false positives (resulting in rejected connections), while helping to ensure
a number of HTTP header based DoS attacks are better handled.
Monitor /var/log/ltm for messages such as:




Sweeper imitated - this means the reapers have kicked in due to high TCP
connection counts and high memory utilization
ICMP messages limited to 250 - Usually a ping or form of ICMP attack
encountered and being mitigated
SYNcookie activated - SYN flood attack encountered
HTTP header size exceeding 32k length - often from SlowLoris or similar HTTP
header attack
Once configured, BIG-IP LTM's approach to network DoS and DDoS attacks is an attack
mitigation configuration that protects core infrastructure when an attack occurs.
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2.12 - Explain how route domains can be used to enforce network
segmentation
Link to Online Topic Content
What is a route domain?
A route domain is a configuration object that isolates network traffic for a particular
application on the network.
Because route domains segment network traffic, you can assign the same IP address or
subnet to multiple nodes on a network, provided that each instance of the IP address
resides in a separate routing domain.
Note: Route domains are compatible with both IPv4 and IPv6 address formats.
Benefits of route domains
Using the route domains feature of the BIG-IP system, you can provide hosting service
for multiple customers by isolating each type of application traffic within a defined
address space on the network.
With route domains, you can also use duplicate IP addresses on the network, provided
that each of the duplicate addresses resides in a separate route domain and is isolated
on the network through a separate VLAN. For example, if you are processing traffic for
two different customers, you can create two separate route domains. The same node
address (such as 10.0.10.1) can reside in each route domain, in the same pool or in
different pools, and you can assign a different monitor to each of the two corresponding
pool members.
Sample route domain deployment
A good example of the use of route domains is a configuration for an ISP that services
multiple customers, where each customer deploys a different application. In this case,
the BIG-IP system isolates traffic for two different applications into two separate route
domains. The routes for each application's traffic cannot cross route domain
boundaries because cross-routing restrictions are enabled on the BIG-IP system by
default.
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A sample route domain deployment
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Section 3 – Deploy applications
Objective - 3.01 Describe how to deploy and modify applications
using existing and/or updated iApp application templates
Link to Online Topic Content
iApps
iApps is the BIG-IP system framework for deploying services-based, template-driven
configurations on BIG-IP systems running TMOS 11.0.0 and later. It consists of three
components: Templates, Application Services, and Analytics. An iApps Template is
where the application is described and the objects (required and optional) are defined
through presentation and implementation language. An iApps Application Service is the
deployment process of an iApps Template which bundles the entire configuration
options for a particular application together. You would have an iApps Application
Service for SharePoint, for example. iApps Analytics include performance metrics on a
per-application and location basis.
Benefits of using iApps:








User-customizable
Easy editing of configurations and cleanup
Reentrancy
Configuration encapsulation
Cradle-to-grave configuration management
Strictness protects against accidental changes to the configuration
Operational tasks and health status for App objects displayed on App-specific
component view (see right)
Copy/Import/Export capability
iApp Components
The iApps framework consists of two main components, application services and
templates.
Application Services
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iApps application services use templates to guide users through configuring new BIG-IP
system configurations. An application service lets an authorized user easily and
consistently deploy complex BIG-IP system configurations just by completing the
information required by the associated template. Every application service is attached
to a specific configuration and cannot be copied the way that iApps templates can.
Templates
iApps templates create configuration-specific forms used by application services to
guide authorized users through complex system configurations. The templates provide
programmatic, visual layout and help information. Each new application service uses
one of the templates to create a screen with fields and help that guide the user through
the configuration process and creates the configuration when finished.
iApps templates allow users to customize by either modifying an existing template or
creating one from scratch. Users can create scratch-built templates using either the
iApps Templates screen or any text-editing software.
Strict Updates Setting
When you are working in the Application Services properties screen, and select the
Advanced view, the Strict Updates field is shown. Selecting Strict Updates protects
against accidental changes to an application service's configuration. The Strict Updates
setting is on by default when an application service is created.
Note: Unless you have a specific reason to turn off strict updates, F5 recommends that you
leave the setting on.
When the strict updates setting is enabled, users can control only objects that are
exposed through the templates. Template reentrancy, covered in the template
authoring, is not recommended if strict updates is turned off.
Note: Even with strict updates enabled, it is possible to enable and disable some objects
using interfaces (such as tmsh or the Configuration Utility) other than the reentrant
template. These objects include:




nodes
pool members
virtual addresses
virtual servers
Deploying an application service
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The following procedure covers the minimum steps needed to deploy a configuration
using an iApps application service.
1.
2.
3.
4.
5.
6.
7.
8.
On the Main tab, expand iApp, and click Application Services.
Click Create.
In the Name field, type the name for your application service.
From the Template List menu, select a template for your application, and wait
for the screen to automatically refresh.
Configure remaining settings as needed.
At the bottom of the screen click Finished to save your changes.
Wait for the application properties to load.
(Optional) In the Description field, enter information to describe this application
service and click Update.
Your application service is now deployed on the BIG-IP system.
Modifying an application service
The following procedure tells how to modify an existing application service.
1. On the Main tab, expand iApp, and click Application Services.
2. From the Application Service List, select an application service to view.
3. Click the Reconfigure tab. The screen displays the settings for the application
service.
4. Click the Components tab and use the components tree to view the components
that belong to the application service.
5. Edit the fields that require modification and then click Finished to save your
changes.
The system saves the application service modifications and they are ready to use.
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3.01 - Identify the appropriate application template to use to deploy the
application
Link to Online Topic Content
Appropriate Application Template
In versions 11.0 - 11.3, the following iApps Templates were shipped with BIG-IP:
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Citrix Presentation Server 4.5
Citrix XenApp 5.0, 5.1 and 6.0
Diameter
DNS Load Balancing
HTTP
IP Forwarding
LDAP
Microsoft Exchange 2010 and 2010 SP1
Microsoft Exchange OWA 2007
Microsoft IIS 7 and 7.5
Microsoft Lync 2010
Microsoft OCS 2007 R2
Microsoft Sharepoint 2010
Microsoft Sharepoint 2007
nPath
Oracle Application Server 10g (and SSO version 10g Release 2 - v10.1.2.0.2)
Oracle EBS 12
Oracle PeopleSoft 9
Oracle WebLogic Server 10.3 (BEA WebLogic 5.1 and 8.1)
Radius
SAP Enterprise Portal 6.0, mySAP ERP 2005
SAP ERP Central Component 6.0, mySAP ERP 2005
VMware View 2.1, 3.0.1, 4.0 and 4.5
There are many application specific templates that you can use that can match the
application for which you are trying to build out configuration. Some of the templates
are more generic to fit a broader set of applications, for example the HTTP template. If
there is not a template that fits your application or you want one specifically for your
application you can try to find a template from the F5 DevCentral website or you can
create your own.
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3.01 - Describe how to locate, retrieve and import new and updated
application templates
Link to Online Topic Content
A good size list of iApps templates come preloaded in the version of TMOS you are
running. As you upgrade to newer versions of TMOS more current iApps templates will
be in the OS build.
There are also supported templates available for download. See the iApps Codeshare
site in the link for this section for an additional list of F5 templates by application. You
can also find community-contributed templates on this site.
To retrieve and install the new template use the following steps:
Installing New iApp Templates


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Download ZIP file containing the new iApp Templates and extract the *.tmpl
file(s)
Log on to the BIG-IP system web-based Configuration utility.
On the Main tab, expand iApp, and then click Templates.
Click the Import button on the right side of the screen.
Click a check in the Overwrite Existing Templates box.
Click the Browse button, and then browse to the location you saved the iApp file.
Click the Upload button. The iApp is now available for use.
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3.01 - Identify use cases for deploying the application templates
Link to Online Topic Content
iApps Use Cases
Use iApps to automate the way you add virtual servers so that you don’t have to go
through the same manual steps every time you add a new application. Or build a
custom iApps to manage your iRules inventory.
iApps gives the administrators of BIG-IP the ability to deploy applications they are not
familiar with by using the templates that are structured around best practice
deployments. This can create configuration consistency when multiple administrators
are working in the same system building configurations for similar applications. iApps
can also cut down on deployment time for new applications. The possibilities are nearly
endless since you have the ability to create your own templates.
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Objective - 3.02 Given application requirements, determine the
appropriate profiles and profile settings to use
3.02 - Describe the connections between profiles and virtual servers
Link to Online Topic Content
Profile Summary:
Profiles are a configuration object containing a logical group of settings for controlling
the behavior of a particular type of network traffic that, when assigned to a virtual
server, define how that traffic should be processed by the virtual server as it is passing
through the virtual server.
Profiles
Profiles are a configuration object that you can use to affect the behavior of certain
types of network traffic. More specifically, a profile is an object that contains settings
with values, for controlling the behavior of a particular type of network traffic, such as
HTTP connections. Profiles also provide a way for you to enable connection and session
persistence, and to manage client application authentication.
By default, Local Traffic Manager provides you with a set of profiles that you can use as
is. These default profiles contain various settings with default values that define the
behavior of different types of traffic. If you want to change those values to better suit
the needs of your network environment, you can create a custom profile. A custom
profile is a profile derived from a default profile and contains values that you specify.
Connection Between Profiles and Virtual Servers
Once you have created a profile for a specific type of traffic, you implement the profile
by associating that profile with one or more virtual servers.
You associate a profile with a virtual server by configuring the virtual server to reference
the profile. Whenever the virtual server receives that type of traffic, Local Traffic
Manager applies the profile settings to that traffic, thereby controlling its behavior.
Thus, profiles not only define capabilities per network traffic type, but also ensure that
those capabilities are available for a virtual server.
Because certain kinds of traffic use multiple protocols and services, users often create
multiple profiles and associate them with a single virtual server.
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For example, a client application might use the TCP, SSL, and HTTP protocols and
services to send a request. This type of traffic would therefore require three profiles,
based on the three profile types TCP, Client SSL, and HTTP.
Each virtual server lists the names of the profiles currently associated with that virtual
server. You can add or remove profiles from the profile list, using the Configuration
utility. Note that Local Traffic Manager has specific requirements regarding the
combinations of profile types allowed for a given virtual server.
In directing traffic, if a virtual server requires a specific type of profile that does not
appear in its profile list, Local Traffic Manager uses the relevant default profile,
automatically adding the profile to the profile list. For example, if a client application
sends traffic over TCP, SSL, and HTTP, and you have assigned SSL and HTTP profiles only,
Local Traffic Manager automatically adds the default profile tcp to its profile list.
At a minimum, a virtual server must reference a profile, and that profile must be
associated with a UDP, FastL4, Fast HTTP, or TCP profile type. Thus, if you have not
associated a profile with the virtual server, Local Traffic Manager adds a UDP, FastL4,
Fast HTTP, or TCP default profile to the profile list.
The default profile that Local Traffic Manager chooses depends on the configuration of
the virtual servers protocol setting. For example, if the protocol setting is set to UDP,
Local Traffic Manager adds the udp profile to its profile list.
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3.02 - Describe profile inheritance
Link to Online Topic Content
Profile Inheritance
Custom profiles have a parent-child relationship with the parent profile used to build
the custom profile. When you make a change to any profile that is used as a parent
profile to another custom profile, the change you make will also change in the custom
profile if it is not a modified value. Meaning that if that value is already set as a custom
value in the custom profile it will remain the custom value and not inherit the changed
parent value.
Custom and Parent Profiles
A custom profile is a profile that is derived from a parent profile that you specify. A
parent profile is a profile from which your custom profile inherits its settings and their
default values.
When creating a custom profile, you have the option of changing one or more setting
values that the profile inherited from the parent profile. In this way, you can pick and
choose which setting values you would like to change and which ones you would like to
retain. An advantage to creating a custom profile is that by doing so, you preserve the
setting values of the parent profile.
Note: If you do not specify a parent profile when you create a custom profile, Local Traffic
Manager automatically assigns a related default profile as the parent profile. For example, if
you create a custom HTTP type of profile, the default parent profile is the default profile
http.
If you do not want to use a default profile as is or change its settings, you can create a
custom profile. Creating a custom profile and associating it with a virtual server allows
you to implement your own specific set of traffic-management policies.
When you create a custom profile, the profile is a child profile and automatically inherits
the setting values of a parent profile that you specify. However, you can change any of
the values in the child profile to better suit your needs.
If you do not specify a parent profile, Local Traffic Manager uses the default profile that
matches the type of profile you are creating.
Important: When you create a custom profile, the BIG-IP system places the profile into your
current administrative partition.
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Important: Within the Configuration utility, each profile creation screen contains a check
box to the right of each profile setting. When you check a box for a setting and then specify
a value for that setting, the profile then retains that value, even if you change the
corresponding value in the parent profile later. Thus, checking the box for a setting ensures
that the parent profile never overwrites that value through inheritance.
Once you have created a custom profile, you can adjust the settings of your custom
profile later if necessary. If you have already associated the profile with a virtual server,
you do not need to perform that task again.
Using the default profile as the parent profile
A typical profile that you can specify as a parent profile when you create a custom
profile is a default profile. For example, if you create a custom TCP-type profile called
my_tcp_profile, you can use the default profile tcp as the parent profile. In this case,
Local Traffic Manager automatically creates the profile my_tcp_profile so that it
contains the same settings and default values as the default profile tcp. The new
custom profile thus inherits its settings and values from its parent profile. You can then
retain or change the inherited setting values in the custom profile to suit your needs.
Using a custom profile as the parent profile
When creating a custom profile, you can specify another custom profile, rather than the
default profile, as the parent profile. The only restriction is that the custom profile that
you specify as the parent must be of the same profile type as the profile you are
deriving from the parent. Once you have created the new custom profile, its settings
and default values are automatically inherited from the custom profile that you
specified as the parent.
For example, if you create a profile called my_tcp_profile2, you can specify the custom
profile my_tcp_profile as its parent. The result is that the default setting values of
profile my_tcp_profile2 are those of its parent profile my_tcp_profile.
If you subsequently modify the settings of the parent profile (my_tcp_profile), Local
Traffic Manager automatically propagates those changes to the new custom profile.
For example, if you create the custom profile my_tcp_profile and use it as a parent
profile to create the custom profile my_tcp_profile2, any changes you make later to the
parent profile my_tcp_profile are automatically propagated to profile my_tcp_profile2.
Conversely, if you modify any of the settings in the new custom profile (in our example,
my_tcp_profile2), the new custom profile does not inherit values from the parent
profile for those particular settings that you modified.
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3.02 - Explain how to configure the different SSL profile settings
SSL profiles
There are two different types of SSL profiles for the BIG-IP system. There is a Client SSL
profile which enables the BIG-IP system to accept and terminate client requests that are
sent using a fully SSL-encapsulated protocol and provides a number of configurable
settings for managing client-side Secure Socket Layer (SSL) connections. There is also a
Server SSL profile which enables the BIG-IP system to initiate secure connections to your
SSL servers by using a fully SSL-encapsulated protocol and providing configurable
settings for managing server-side SSL connections.
You can use the default SSL client and Server
The following sections will describe in depth the different settings in each SSL profile
type.
Link to Online Topic Content
Client SSL Profile
General Properties
Setting
Description
Name
The Name setting is required. To create a Client SSL profile, you must
specify a unique name for the profile.
This setting specifies an existing profile to use as the parent profile. A
profile inherits settings from its parent, unless you override the setting by
selecting its Custom box and modifying the value. The default is clientssl
profile.
Parent
Profile
Configuration
This section describes the most commonly used SSL settings for a Client SSL profile, for
example, the certificate and key to send to SSL clients for certificate exchange.
Setting
Description
Certificate
The Certificate setting (Certificate Key Chain in BIG-IP 11.5.0 and
later) is required. By default, the Client SSL profile uses a self-signed
certificate, named default.crt. However, this field is almost always
customized to reference a certificate that is specific to the site to
which the profile will be applied. The SSL certificate must be in PEM
format and must be imported to the BIG-IP system with the
corresponding key before they can be referenced by an SSL profile.
For information about importing an SSL certificate and key using the
Configuration utility, refer to SOL14620: Managing SSL certificates
for BIG-IP systems. For information about importing an SSL
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Key
Passphrase
Chain
Ciphers
Options
Options List
Proxy SSL
certificate and key using the Traffic Management Shell (tmsh) utility,
refer to SOL14031: Importing the SSL certificate and key using the
Traffic Management Shell.
For information about verifying the certificate format, refer to
SOL13349: Verifying SSL certificate and key pairs from the command
line (11.x)
After importing the SSL certificate and matching key to the BIG-IP
system, choose the appropriate certificate from the Certificate
setting.
The Key setting is required. By default, the Client SSL profile uses
the built-in key, named default.key, which matches default.crt. You
must choose the key that matches the configured certificate and the
key must be in PEM format. After importing the SSL certificate and
matching key to the BIG-IP system, choose the appropriate key from
the Key setting.
The Passphrase setting is optional. It is only required if the key is
passphrase-protected. There is no default value for this setting. If
your key is passphrase-protected, enter the required passphrase.
The Chain setting is optional. This setting is used to specify a
certificate bundle or chain the client can use to establish a trust
relationship with a server that presents a certificate signed by an
untrusted Certificate Authority (CA). The default value for the Chain
setting is None, indicating that no chain certificate will be presented
to the client with the server SSL certificate. This setting lists the
name of all the SSL certificates installed in the BIG-IP system's SSL
certificate store. If you are using certificates signed by an
Intermediate CA, F5 recommends that you create and install a bundle
that contains the certificates for all of the CAs in the chain between
the certificate configured in the SSL profile and a root CA whose
certificate is trusted by the expected client base. The new certificate
bundle can then be selected in the Chain setting. For information
about creating and installing a custom certificate bundle, refer to
SOL13302: Configuring the BIG-IP system to use an SSL chain
certificate (11.x).
Note: Regardless of the Chain setting, if the Trusted Certificate
Authorities setting is configured, the certificate bundle contained in
the configured Trusted Certificate Authorities file is presented.
The Ciphers setting is optional. By default, the Client SSL profile
uses the DEFAULT cipher string. In most cases, the
DEFAULT cipher string is appropriate, but can be customized as
necessary to meet the security and performance needs of your site.
For information about configuring the SSL cipher for an SSL profile,
refer to SOL13171: Configuring the cipher strength for SSL profiles
(11.x).
When enabled (Options List), references the Options List setting,
which industry standard SSL options and workarounds use for
handling SSL processing. The default setting is All Options
Disabled.
The Options List setting provides selection from a set of industry
standard SSL options and workarounds for handling SSL processing.
The Proxy SSL setting was introduced in BIG-IP 11.0.0. By default,
the Proxy SSL setting is disabled (cleared). When enabled, the client
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ModSSL
Methods
Cache Size
Cache Timeout
Alert Timeout
Handshake
Timeout
Renegotiation
Renegotiation
Period
Renegotiation
Size
is allowed to directly authenticate with the server, and the server can
authenticate with the client, based on the client certificate presented.
In a typical setup, with the BIG-IP system in the middle, the client and
server cannot communicate directly to authenticate each other. The
Proxy SSL setting requires both a Client SSL profile and a Server
SSL profile, and must be enabled in both profiles. For information
about the Proxy SSL setting, refer to the following resources:
1. SOL13385: Overview of the Proxy SSL feature
2. The Implementing Proxy SSL on a Single BIG-IP system
chapter of the BIG-IP LTM Implementations guide.
ModSSL Methods enables or disables ModSSL method emulation.
Enable this option when OpenSSL methods are inadequate, for
example, when you want to use SSL compression over TLSv1. By
default, this setting is disabled (cleared).
The Cache Size setting specifies the maximum number of SSL
sessions allowed in the SSL session cache. The default value for
Cache Size is 262144 sessions. For information about the SSL
Cache Size settings, refer to SOL6767: Overview of the BIG-IP SSL
session cache profile settings.
The Cache Timeout setting specifies the number of seconds that
SSL sessions are allowed to remain in the SSL session cache before
being removed. The default value for Cache Timeout is 3600
seconds. The range of values configurable for Cache Timeout is
between 0 and 86400 seconds inclusive.
Note: Longer cache time-out periods can increase the risk of SSL
session hijacking.
The Alert Timeout setting specifies the duration that the system tries
to close an SSL connection by transmitting an alert or initiating an
unclean shutdown before resetting the connection. The default value
for BIG-IP 11.2.0 and later is 10 seconds. The default value for
11.0.0 through 11.1.0 is 60 seconds. Select Indefinite to specify
that the connection should not be reset after transmitting an alert or
initiating an unclean shutdown.
The Handshake Timeout setting specifies the number of seconds
that the system tries to establish an SSL connection before
terminating the operation. The default value for BIG-IP 11.2.0 and
later is 10 seconds. The default value for 11.0.0 through 11.1.0 is 60
seconds. Selecting Indefinite specifies that the system continues
trying to establish a connection for an unlimited time.
The Renegotiation setting can be configured to control whether the
virtual server allows midstream session renegotiation. When
Renegotiation is enabled, the BIG-IP system processes mid-stream
SSL renegotiation requests. When disabled, the system terminates
the connection, or ignores the request, depending on system
configuration. By default, this setting is enabled (selected).
The amount of time in seconds from the initial connection before the
system renegotiates the SSL session. Indefinite will not renegotiate
the SSL session and is the default setting.
The amount of application data in megabytes from the initial
connection before the system renegotiates the SSL session.
Indefinite will not renegotiate the SSL session and is the default
setting.
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Renegotiate
Max Record
Delay
Secure
Renegotiation
Server Name
Default SSL
Profile for SNI
Require Peer
SNI Support
Unclean
Shutdown
The number of SSL records allowed during the SSL renegotiation
before the system terminates the connection. Indefinite allows an
unlimited number and is the default setting. The Renegotiation Max
Record Delay option was introduced in BIG-IP version 11.6.0.
The BIG-IP SSL profiles support the TLS Renegotiation Indication
Extension, which allows the user to specify the method of secure
renegotiation for SSL connections. The default value for the Client
SSL profile is Require. The values for the Secure Renegotiation
setting in the Client SSL profile are as follows:
1. Request: Specifies that the system requests secure renegotiation
of SSL connections.
2. Require: Specifies that the system requires secure renegotiation of
SSL connections. In this mode, the system permits initial SSL
handshakes from clients, but terminates renegotiations from
clients that do not support secure renegotiation.
3. Require Strict: Specifies that the system requires strict, secure
renegotiation of SSL connections. In this mode, the system
denies initial SSL handshakes from clients that do not support
secure renegotiation.
Starting in BIG-IP 11.1.0, the BIG-IP SSL profiles support the TLS
Server Named Indication (SNI) Extension, which allows the BIG-IP
system to select the appropriate SSL profile based on the TLS SNI
information provided by the client. The Server Name setting
specifies the fully qualified DNS hostname of the server (or a wildcard
string containing the asterisk '*' character to match multiple names)
used in the TLS SNI connection. There is no default value for this
setting. For information about configuring the TLS SNI feature on the
BIG-IP system, refer to SOL13452: Configuring a virtual server to
serve multiple HTTPS sites using TLS Server Name Indication
feature.
When enabled, this setting indicates that the profile should be used
as the default SSL profile when there is no match to the server name,
or when the client does not support TLS SNI extension. By default,
this setting is disabled (cleared). For information about configuring
the TLS SNI feature on the BIG-IP system, refer to SOL13452:
Configuring a virtual server to serve multiple HTTPS sites using TLS
Server Name Indication feature.
When enabled, this setting requires that the client must support the
TLS SNI extension; otherwise, the BIG-IP system disconnects the
client connection with a fatal alert. By default, this setting is disabled
(cleared).
The SSL protocol performs a clean shutdown of an active TLS/SSL
connection by sending a close notify alert to the peer system. The
Unclean Shutdown setting allows the BIG-IP system to perform an
unclean shutdown of SSL connections by closing the underlying TCP
connection without sending the SSL close notify alerts. By default,
this setting is enabled (selected) and is useful for certain browsers
that handle SSL shutdown alerts differently. For example, some
versions of Internet Explorer require SSL shutdown alerts from the
server while other versions do not, and the SSL profile cannot always
detect this requirement.
Important: If you disable (clear) the Unclean Shutdown setting,
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Strict Resume
Non-SSL
Connections
some browsers may display blank pages or errors when connecting
to the virtual server.
The Strict Resume setting enables or disables the resumption of
SSL sessions after an unclean shutdown. By default, this setting is
disabled (cleared).
Enables or disables acceptance of non-SSL connections. By default,
the acceptance of non-SSL sessions is disabled (cleared).
Client Authentication
The Client Authentication section of the Client SSL profile is specific to client certificate
authentication. Some applications require clients to establish their identity to the
server before proceeding with the SSL session. Client certificate authentication uses the
following sequence of events:


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


The client requests an SSL connection.
The SSL server presents its SSL certificate, and any configured chain certificate
bundle, to the client.
The SSL client uses the CA certificates stored in its Trusted Device Certificate
store, and the supplied certificate chain, if necessary, to authenticate the server.
The SSL server requests a client certificate, advertising a list of preferred CAs if
configured to do so.
The SSL client presents its SSL certificate.
The SSL server uses its configured, trusted CA certificate bundle, to authenticate
the client.
Setting
Description
Client
Certificate
The Client Certificate setting is required. This setting is used to
enable and disable client certificate authentication. The possible
options for the Client Certificate setting are:
3. Ignore: The Ignore setting is the default setting. It disables Client
Certificate Authentication. The BIG-IP system ignores any
certificate presented and does not authenticate the client before
establishing the SSL session.
4. Request: The Request setting enables optional Client Certificate
Authentication. The BIG-IP system will request a client
certificate and attempt to verify it. However, an SSL session is
established regardless of whether or not a valid client certificate
from a trusted CA was presented. The Request setting is often
used in conjunction with iRules to provide selective access
depending on the certificate presented. For example, this option
would be useful if you would like to allow clients who present a
certificate from the configured trusted CA to gain access to the
application, while clients who do not provide the required
certificate are redirected to a page that details the access
requirements. However, if you are not using iRules to enforce a
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Frequency
Certificate
Chain
Traversal
Depth
Trusted
Certificate
Authorities
different outcome, depending on the certificate details, there is
no functional benefit to using the Request setting instead of the
default Ignore setting. In both cases, an SSL session is
established, regardless of the certificate presented, and the
connection is proxied to the default pool.
5. Require: The Require setting enforces Client Certificate
Authentication. The BIG-IP system will request a client
certificate and attempt to verify it. An SSL session is
established only if a valid client certificate from a trusted CA was
presented. The Require setting is used to restrict access to
only clients that present a valid certificate from a trusted CA.
Note: The Auto setting was removed in BIG-IP 11.0.0.
The Frequency setting specifies the frequency of client authentication
for an SSL session. The default value for this setting is once.
The Certificate Chain Traversal Depth setting specifies the maximum
number of certificates to be traversed in a client certificate chain. The
default value is 9.
The Trusted Certificate Authorities setting is required only if the BIGIP system performs Client Certificate Authentication. This setting is
used to specify the BIG-IP system's Trusted Certificate Authorities store
(the CAs that the BIG-IP system trusts when the system verifies a client
certificate that is presented during Client Certificate Authentication).
The default value for the Trusted Certificate Authorities setting is
None, which indicates that no CAs are trusted. The None value is only
appropriate if Client Certificate Authentication is not desired. Unless it
is performing Client Certificate Authentication, the SSL server does not
need to trust any CA. If the BIG-IP Client Certificate Mode is set to
Require, but Trusted Certificate Authorities is set to None, clients
cannot establish SSL sessions with the virtual server. This setting lists
the name of all the SSL certificates installed on the BIG-IP system.
The ca-bundle certificate may be appropriate for use as a Trusted
Certificate Authorities certificate bundle. However, if this bundle is
specified as the Trusted Certificate Authorities certificate store, any
valid client certificate that is signed by one of the popular Root CAs
included in the default ca-bundle.crt is authenticated. This provides
some level of identification, but very little access control because
almost any valid client certificate could be authenticated. However, it is
more common when configuring client certificate authentication to
accept client certificates from one, or a select few, PKIs or private CAs.
If you want to trust only certificates signed by a specific CA or set of
CAs, F5 recommends that you create and install a bundle that contains
trustworthy CA certificates. The new certificate bundle can then be
selected in the Trusted Certificate Authorities setting. For
information about creating a custom certificate bundle, refer to
SOL13302: Configuring the BIG-IP system to use an SSL chain
certificate (11.x).
The bundle must also include the entire chain of CA certificates
necessary to establish a chain of trust, as described in the Chain
setting. To support multiple PKI hierarchies, this bundle can contain CA
certificates from several different PKIs. The bundle does not need to
contain CA certificates from the PKI that signed the server SSL
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certificate, unless client SSL certificates from that PKI must be validated
by the BIG-IP system. However, in practice, Client Certificate
Authentication is most commonly used with Private PKIs, and the
Trusted Certificate Authorities setting often contains only a certificate
or chain from the PKI that signed the server certificate.
You can use the openssl command to verify the client certificate
against the Trusted Certificate Authority bundle prior to importing it onto
the BIG-IP system. For example, the following openssl command
verifies the client certificate, client.crt, against the Trusted Certificate
Authority bundle:
openssl verify -purpose sslclient -CAfile
/path/to/trusted-ca-bundle.crt
/path/to/client.crt
If the chain of trust can be established for the server certificate using
the specified chain, the command returns output, similar to the following
example:
client.crt: OK
Advertised
Certificate
Authorities
Important: Configuring the Trusted Certificate Authorities setting has
no effect on client validation of the SSL server certificate that the BIG-IP
system presents upon connection to an SSL virtual server. It is the SSL
client's responsibility to verify the validity of the SSL server's certificate
using its own Trusted Certificate store. However, the certificate bundle
contained in the configured Trusted Certificate Authorities file is
presented with the server SSL certificate, regardless of the Chain
setting.
The Advertised Certificate Authorities setting is optional. It is used
to specify the CAs that the BIG-IP system advertises as trusted when
soliciting a client certificate for client certificate authentication. If the
Client Certificate setting is configured to Require or Request, you can
configure the Advertised Certificate Authorities setting to send
clients a list of CAs that the server is likely to trust. The default value
for the Advertised Certificate Authorities setting is None, indicating
that no CAs are advertised. When set to None, no list of trusted CAs is
sent to a client with the certificate request. This setting lists the name
of all the SSL certificates installed on the BIG-IP system. If you want to
advertise only a specific CA, or set of CAs, F5 recommends that you
create and install a bundle that contains the certificates of the CA to
advertise. You can then select the new certificate bundle in the
Advertised Certificate Authorities setting. For information about
creating a custom certificate bundle, refer to SOL13302: Configuring
the BIG-IP to use an SSL chain certificate (11.x).
You can configure the Advertised Certificate Authorities setting to
send a different list of CAs than that specified for the Trusted Certificate
Authorities. This allows greater control over the configuration
information shared with unknown clients. You might not want to reveal
the entire list of trusted CAs to a client that does not automatically
present a valid client certificate from a trusted CA. Although the two
settings can be configured differently, in most cases, you should
configure the Advertised Certificate Authorities setting to use the
same certificate bundle as the Trusted Certificate Authorities setting.
Important: Avoid specifying a bundle that contains many certificates
when configuring the Advertised Certificate Authorities setting. This
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minimizes the number of certificates that must be exchanged during a
client SSL handshake. The maximum size allowed by the BIG-IP
system for native SSL handshake messages is 14,304 bytes. Although
typical handshakes do not result in excessive message length, if the
SSL handshake is negotiating a native cipher, and the total length of all
messages in the handshake exceeds this byte threshold, the
handshake will fail.
The Certificate Revocation List (CRL) setting allows you to specify a
CRL that the BIG-IP system should use to check revocation status of a
certificate prior to authenticating a client. If you want to use a CRL, you
must import it to the BIG-IP system. The name of the CRL file can then
be entered in the Certificate Revocation List (CRL) setting dialog box.
For information about importing an SSL CRL file, refer to SOL14620:
Managing SSL certificates for BIG-IP systems. Since CRLs can quickly
become outdated, F5 recommends that you use either OCSP or
CRLDP profiles for more robust and current verification functionality.
Certificate
Revocation
List (CRL)
Link to Online Topic Content
Server SSL Profile
General Properties
Setting
Description
Name
The Name setting is required. To create a Server SSL profile, you must
specify a unique name for the profile. For more information about the profile
name requirements, refer to the following articles:
6. SOL6869: Reserved words that should not be used in BIG-IP
configurations
7. SOL13209: BIG-IP configuration object names must begin with an
alphabetic character
This setting specifies an existing profile to use as the parent profile. A
profile inherits settings from its parent, unless you override the setting by
selecting its Custom box and modifying the value. The default is serverssl
profile.
Parent
Profile
Configuration
This section describes the most common SSL settings for a Server SSL profile, for
example, the certificate and key to send to SSL servers for certificate exchange.
Setting
Description
Certificate
The Certificate setting is optional. The default value for this setting is
None. When you apply a Server SSL profile to a virtual server, the
BIG-IP system acts as an SSL client. If you do not intend for the BIGIP system to present its client certificate on behalf of clients traversing
the virtual server, select None. If you expect the BIG-IP system to
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Key
Passphrase
Chain
Ciphers
Options
Options List
present a client certificate, import the certificate and matching key to
the BIG-IP system, and then choose the appropriate certificate from
the menu. For information about importing an SSL certificate and key
by using the Configuration utility, refer to SOL14620: Managing SSL
certificates for BIG-IP systems. For information about importing an
SSL certificate and key using the Traffic Management Shell (tmsh)
utility, refer to SOL14031: Importing the SSL certificate and key using
the Traffic Management Shell.
For information about verifying the certificate format, refer to
SOL13349: Verifying SSL certificate and key pairs from the command
line (11.x)
The Key setting is required only for configured certificates. If you
have configured a certificate, you must choose the key that matches
the configured certificate. The default value for this setting is None.
The Passphrase setting is optional. It is only required if the key is
passphrase-protected. There is no default value for this setting. If a
key is specified and the key is passphrase protected, enter the
required passphrase. When no passphrase is configured, the
Passphrase field displays an eight-asterisk mask (********), giving the
appearance that an eight-character password has been configured.
The passphrase is encrypted before it is saved in the bigip.conf file.
The Chain setting is optional. This setting is used to specify a
certificate bundle or chain that the server can use to establish a trust
relationship with a client that presents a certificate signed by an
untrusted Certificate Authority (CA). The default value for the Chain
setting is None, indicating that the BIG-IP system will not present a
chain certificate with its client SSL certificate. This setting lists the
name of all the SSL certificates installed in the BIG-IP system's SSL
certificate store. If the certificate configured in the Server SSL profile
is signed by an Intermediate CA, F5 recommends that you create and
install a bundle that contains the certificates of all the CAs in the chain
between the certificate configured in the Server SSL profile and a root
CA whose certificate is trusted by your SSL servers. The new
certificate bundle can then be selected in the Chain setting. For
information about creating and installing a custom certificate bundle,
refer to SOL13302: Configuring the BIG-IP system to use an SSL
chain certificate (11.x).
The Ciphers setting is optional. By default, the Server SSL profile
uses the DEFAULT cipher string. In most cases, the default setting is
appropriate, but can be customized, as necessary, to meet the
security and performance needs of your site. The SSL server selects
the cipher used in a particular connection from the ciphers presented
by the SSL client. When using Server SSL, the BIG-IP system acts
as an SSL client. Although the server decides which cipher to use,
you can gain some control by customizing the ciphers presented by
the client. For information about configuring the SSL cipher for an
SSL profile, refer to SOL13171: Configuring the cipher strength for
SSL profiles (11.x).
When enabled, (Options List) references the Options List setting,
which industry standard SSL options and workarounds for handling
SSL processing. The default setting is All Options Disabled.
The Options List setting provides selection from a set of industry
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Proxy SSL
ModSSL
Methods
Cache Size
Cache Timeout
Alert Timeout
Handshake
Timeout
Renegotiation
Renegotiation
Period
standard SSL options and workarounds for handling SSL processing.
The Proxy SSL setting was introduced in BIG-IP 11.0.0. By default,
the Proxy SSL setting is disabled (cleared). When enabled, the client
is allowed to directly authenticate with the server, and the server can
authenticate with the client, based on the client certificate presented.
In a typical setup with the BIG-IP system in the middle, the client and
server cannot communicate directly to authenticate each other. The
Proxy SSL setting requires both a Client SSL profile and a Server
SSL profile, and must be enabled in both profiles. For information
about the Proxy SSL setting, refer to the following resources:
8. SOL13385: Overview of the Proxy SSL feature
9. The Implementing Proxy SSL on a Single BIG-IP system chapter
of the BIG-IP LTM Implementations guide.
The ModSSL Methods setting enables or disables ModSSL method
emulation. Enable this option when OpenSSL methods are
inadequate, for example, when you want to use SSL compression
over TLSv1. By default, this setting is disabled (cleared).
The Cache Size setting specifies the maximum number of SSL
sessions allowed in the SSL session cache. The default value for the
Cache Size setting is 262144 sessions. For information about the
SSL Cache Size settings, refer to SOL6767: Overview of the BIG-IP
SSL session cache profile settings.
The Cache Timeout setting specifies the number of seconds that
SSL sessions are allowed to remain in the SSL session cache before
being removed. The default value for the Cache Timeout setting is
3600 seconds. The range of values configurable for the Cache
Timeout setting is between 0 and 86400 seconds, inclusive.
The Alert Timeout setting specifies the duration that the system tries
to close an SSL connection by transmitting an alert or initiating an
unclean shutdown before resetting the connection. The default value
for this setting in BIG-IP 11.2.0 and later is 10 seconds. The default
value for this setting in BIG-IP 11.0.0 through 11.1.0 is 60 seconds.
You can select Indefinite to specify that the connection should not be
reset after transmitting an alert or initiating an unclean shutdown.
The Handshake Timeout setting specifies the number of seconds
that the system tries to establish an SSL connection before
terminating the operation. The default value for this setting in BIG-IP
11.2.0 and later is 10 seconds. The default value for this setting in
BIG-IP 11.0.0 through 11.1.0 is 60 seconds. You can select
Indefinite to specify that the system should continue to try and
establish a connection for an unlimited time.
You can configure the Renegotiation setting to control whether the
virtual server allows midstream session renegotiation. When
Renegotiation is enabled, the BIG-IP system processes mid-stream
SSL renegotiation requests. When Renegotiation is disabled, the
system terminates the connection, or ignores the request, depending
on the system configuration. By default, this setting is enabled
(selected).
You can configure the Renegotiate Period setting to control the
amount of time, in seconds, that the system waits before renegotiating
the SSL session. By default, this setting is set to Indefinite. When
this setting is set to Indefinite, the system does not renegotiate SSL
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Renegotiation
Size
Secure
Renegotiation
Server Name
Default SSL
Profile for SNI
Require Peer
SNI support
Unclean
Shutdown
Strict Resume
sessions based on a specified time interval.
The Renegotiate Size setting controls the amount of data exchange,
in megabytes, before the system renegotiates the SSL session. By
default, this setting is set to Indefinite. When this setting is set to
Indefinite, the system does not renegotiate SSL sessions based on
the amount of exchanged data.
The BIG-IP SSL profiles support the TLS Renegotiation Indication
Extension, which allows the user to specify the method of secure
renegotiation for SSL connections. The default value for the Server
SSL profile is Require Strict. The values for the Secure
Renegotiation setting in the Server SSL profile are as follows:
4. Request: Specifies that the system requests secure renegotiation
of SSL connections.
5. Require: Specifies that the system requires secure renegotiation of
SSL connections. In this mode, SSL connections initiated from
the system to an unpatched server fail when renegotiation is
enabled.
6. Require Strict: Specifies that the system requires strict, secure
renegotiation of SSL connections. In this mode, SSL
connections that are initiated from the system to an unpatched
server fail when renegotiation is enabled.
Within the context of the Server SSL profile, there is no behavioral
difference between the Require and Require Strict settings. In either
mode, initial SSL connections from the BIG-IP system to unpatched
servers fail.
Starting in BIG-IP 11.1.0, the BIG-IP SSL profiles support the TLS
Server Named Indication (SNI) Extension, which allows the BIG-IP
system to send ClientHello messages with SNI extension. The
Server Name setting specifies the fully qualified DNS hostname of the
server (or a wildcard string containing the asterisk '*' character to
match multiple names) used in the TLS SNI connection. There is no
default value for this setting.
When enabled, this setting indicates that the system should use the
profile as the default SSL profile for connecting to the server. By
default, this setting is disabled (cleared).
When enabled, this setting requires that the server must support the
TLS SNI extension; otherwise, the BIG-IP system disconnects the
SSL connection with a fatal alert. By default, this setting is disabled
(cleared).
The SSL protocol performs a clean shutdown of an active TLS/SSL
connection by sending a close notify alert to the peer system. The
Unclean Shutdown setting allows the BIG-IP system to perform an
unclean shutdown of SSL connections by closing the underlying TCP
connection without sending the SSL close notify alerts. By default,
this setting is enabled (selected).
The Strict Resume setting enables or disables the resumption of SSL
sessions after an unclean shutdown. By default, this setting is
disabled (cleared).
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Server Authentication
The Server Authentication section of the Server SSL profile provides configurable
settings for handling server authentication before proceeding with the SSL session.
Setting
Description
Server
Certificate
The Server Certificate setting specifies how the system handles
server certificates. The possible values for the Server Certificate
setting are:
10.
Ignore: The Ignore setting is the default setting. The BIG-IP
system ignores certificates from the server and never
authenticates the server.
11.
Require: The Require setting enforces server authentication.
The BIG-IP system requires the server to present a valid
certificate before establishing the SSL session. If you select
Require as the Server Certificate setting, you must also
specify a value in the Authenticate Name setting. A blank
Authenticate Name setting indicates that all servers are
authenticated, even though you have specified Require as the
Server Certificate setting.
The Frequency setting specifies the frequency of server
authentication for an SSL session. The default value for this setting is
Once, which causes the system to authenticate the server for an SSL
session only once. When you configure this setting to Always, the
system authenticates the server for an SSL session and every
subsequent reuse of the SSL session.
The Certificate Chain Traversal Depth setting specifies the
maximum number of certificates that the system traverses in a server
certificate chain. The default value is 9.
This setting specifies a Common Name (CN) that is embedded in a
server certificate. The system authenticates a server based on the
specified CN. There is no default value for this setting.
The Trusted Certificate Authorities setting is optional. The system
uses this setting to specify the CAs that the BIG-IP system trusts
when verifying a server certificate. The default value for this setting is
None, which causes the system to accept a server certificate signed
by any CA. If you select Require for the Server Certificate setting,
you must specify a CA from the Trusted Certificate Authorities
setting. The selected CA will be trusted by the system when verifying
a server certificate.
Frequency
Certificate
Chain Traversal
Depth
Authenticate
Name
Trusted
Certificate
Authorities
The ca-bundle certificate may be appropriate for use as a Trusted
Certificate Authorities certificate bundle. However, if this bundle is
specified as the Trusted Certificate Authorities certificate store, any
valid server certificate that is signed by one of the popular root CAs
included in the default ca-bundle.crt is authenticated. This provides
some level of identification, but very little access control because
almost any valid server certificate could be authenticated.
If you want to trust only a server certificate that has been signed by a
private PKI or set of private PKIs, F5 recommends that you create and
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install a custom certificate bundle that contains the private PKI
certificates, including the CA that directly signed your servers'
certificates. You can then select the new certificate bundle in the
Trusted Certificate Authorities setting. For information about
creating a custom certificate bundle, refer to SOL13302: Configuring
the BIG-IP system to use an SSL chain certificate (11.x).
Certificate
Revocation List
(CRL)
Important: Configuring the Trusted Certificate Authorities setting
has no effect on server validation of the SSL server certificate that the
BIG-IP system presents when connecting to an SSL server. The SSL
server is responsible for verifying the validity of the SSL client's
certificate using its own Trusted Certificate store. If you need to
specify a chain of trust to support the SSL server's verification of the
BIG-IP system's client certificate, refer to your SSL server
documentation for configuration details.
The Certificate Revocation List (CRL) setting allows you to specify
a CRL that the BIG-IP system should use to check revocation status
of a certificate before the system authenticates a server. If you want
to use a CRL, you must import it to the BIG-IP system. You can then
select the name of the CRL file from the Certificate Revocation List
(CRL) setting. For information about importing an SSL CRL file, refer
to SOL14620: Managing SSL certificates for BIG-IP systems.
Because CRLs can quickly become outdated, F5 recommends that
you use either OCSP or CRLDP profiles for more robust and current
verification functionality.
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3.02 - Explain the effect of changing protocol settings
Link to Online Topic Content
Protocol Settings
Protocol profiles support parameters concerning timeouts in connection management.
Making changes to these profiles directly affects the behaviors connections at layer 4 for
the associated virtual server. If the protocol profile is currently being used and you
make a change to the profile it can break the existing layer 4 connections using that
profile. Making a change to a parent protocol profile can not only affect the
connections using that profile where it is assigned but also any connections using a child
of that parent profile.
All virtual servers have at least one protocol profile associated with them. While the
HTTP Class is a protocol profile for configuration purposes, it cannot be the sole profile
of any virtual server and must always be combined with both the TCP and HTTP profile.
The protocol profiles types are:






Fast L4
Fast HTTP
HTTP Class
TCP
UDP
SCTP
For each protocol profile type, Local Traffic Manager provides a pre-configured profile
with default settings. In most cases, you can use these default profiles as is. If you want
to change these settings, you can configure protocol profile settings when you create a
profile, or after profile creation by modifying the profiles settings.
You can see all of the settings for each of the protocol profiles types below. It is quite
long and understanding the description will help you to understand the impact.
The Fast L4 profile type
The purpose of a Fast L4 profile is to help you manage Layer 4 traffic more efficiently.
When you assign a Fast L4 profile to a virtual server, the Packet Velocity® ASIC (PVA)
hardware acceleration within the BIG-IP system can process some or all of the Layer 4
traffic passing through the system. By offloading Layer 4 processing to the PVA
hardware acceleration, the BIG-IP system can increase performance and throughput for
basic routing functions (Layer 4) and application switching (Layer 7).
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You can use a Fast L4 profile with these types of virtual servers: Performance (Layer 4),
Forwarding (Layer 2), and Forwarding (IP).
This table lists and describes the settings of a Fast L4 profile.
Settings of a Fast L4 profile
Setting
Description
Name
This setting specifies a unique name for the profile.
Parent Profile
This setting specifies the profile that you want to use as
the parent profile. Your new profile inherits all noncustom settings and values from the parent profile
specified.
If this setting is enabled and a TCP connection exceeds
the timeout value for idle connections, the BIG-IP system
sends a reset in addition to deleting the connection.
If this setting is enabled, the BIG-IP system reassembles
IP fragments.
This setting specifies the number of seconds that a
connection is idle before the connection is eligible for
deletion. For background information on setting idle
timeout values, see Chapter 1, Introducing BIG-IP Local
Traffic Manager.
Specify: Specifies the acceptable duration for a TCP
handshake, that is, the maximum idle time between a
client SYN and a client ACK. If the TCP handshake takes
longer than the timeout, the system automatically closes
the connection.
Disabled: Specifies that the system does not apply a
timeout to a TCP handshake.
Indefinite: Specifies that the acceptable duration for a
TCP handshake is indefinite.
Overrides the maximum segment size (MSS), which is
1460. Possible values are:
Disabled: Specifies that you want the maximum segment
size to remain at 1460.
Specify. Permits you to override the maximum segment
size (1460) by specifying a number. Note that specifying
a 0 value is equivalent to retaining the default value
(Disabled).
This setting specifies the maximum acceleration mode
that you prefer the system to use. Note that depending
on the virtual server configuration, the system might or
might not accelerate traffic in this mode. Possible values
are Full, Assisted, or None. Additional information on
this setting follows this table.
This setting specifies the Type of Service level that the
BIG-IP system assigns to IP packets when sending them
to clients.
Reset on
Timeout
Reassemble IP
Fragments
Idle Timeout
TCP
Handshake
Timeout
Max Segment
Size Override
PVA
Acceleration
IP ToS to Client
Default
Value
No
default
value
fastL4
Enabled
Disabled
300
5
Disabled
Full
Pass
Through
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IP ToS to
Server
Link QoS to
Client
Link QoS to
Server
TCP
Timestamp
Mode
TCP Window
Scale Mode
Generate
Internal
Sequence
Numbers
Strip Sack OK
RTT from Client
RTT from
Server
Loose Initiation
Loose Close
TCP Close
Timeout
TCP Keep Alive
Interval
Hardware SYN
Cookie
Protection
Software SYN
This setting specifies the Type of Service level that the
BIG-IP system assigns to IP packets when sending them
to servers
This setting specifies the Quality of Service level that the
BIG-IP system assigns to IP packets when sending them
to clients.
This setting specifies the Quality of Service level that the
BIG-IP system assigns to IP packets when sending them
to servers.
Specifies the action that the BIG-IP system should take
on TCP timestamps. Possible values are: Preserve,
Strip, and Rewrite.
Specifies the action that the BIG-IP system should take
on TCP windows. Possible values are: Preserve and
Strip.
Enables the BIG-IP system to generate its own sequence
numbers for SYN packets, according to RFC 1948.
Pass
Through
Enables the BIG-IP system to block a TCP SackOK
option from passing to the server on an initiating SYN.
Specifies that the BIG-IP system should use TCP
timestamp options to measure the round-trip time to the
client.
Specifies that the BIG-IP system should use TCP
timestamp options to measure the round-trip time to the
server.
Specifies, when checked (enabled), that the system
initializes a connection when it receives any TCP packet,
rather that requiring a SYN packet for connection
initiation. The default is disabled. We recommend that if
you enable the Loose Initiation setting, you also enable
the Loose Close setting.
Important: Enabling loose initiation can permit stray
packets to pass through the system. This can pose a
security risk and reduce system performance.
Specifies, when checked (enabled), that the system
closes a loosely-initiated connection when the system
receives the first FIN packet from either the client or the
server.
Specifies the length of time in seconds that a connection
can remain idle before deletion, once the system receives
a CLOSE packet for that connection. The TCP Close
Timeout value must be less than the Idle Timeout value.
Also, for the TCP Close Timeout value to be valid, you
must have the Loose Close setting enabled.
Specifies the keep-alive probe interval, in seconds.
Disabled
Enables or disables hardware SYN cookie protection
when PVA10 is present on the system. This feature is
available on certain hardware platforms only.
Enables or disables software SYN cookie protection when
Disabled
Pass
Through
Pass
Through
Preserve
Preserve
Disabled
Disabled
Disabled
Disabled
Disabled
5
Disabled
Disabled
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Cookie
Protection
PVA10 is not present on the system.
PVA hardware acceleration
Once you implement a Fast L4 profile, Local Traffic Manager automatically selects the
most efficient PVA hardware acceleration mode for Layer 4 traffic. Possible modes are
Full, Assisted, and None.
The particular hardware acceleration mode that Local Traffic Manager selects depends
on these factors:

The Fast L4 profile settings
The mode that the BIG-IP selects is influenced by the way that you configure the
settings of the Fast L4 profile.

The virtual server configuration
The mode that Local Traffic Manager selects is influenced by the specific features
that you assigned to the virtual server (such as pools, SNAT pools, and iRules).

A monitor assigned to associated nodes
For full PVA acceleration, you must assign monitors to the relevant nodes.

The value of the PVA Acceleration setting
The PVA Acceleration setting in the Fast L4 profile defines the maximum amount
of hardware acceleration that you want to allow, for Layer 4 traffic passing
through the virtual server. Therefore, if you set the value to:
Full: The system can set hardware acceleration to any of the three modes (Full,
Assisted, or None), depending on the virtual server configuration. This is the
default value.
Assisted: The system can set hardware acceleration to either Assisted or None
mode, depending on the virtual server configuration.
None: The system does not perform hardware acceleration.
Depending on the current mode to which hardware acceleration is automatically set,
Local Traffic Manager accelerates Layer 4 traffic as described in the following table.
Effect of PVA hardware acceleration mode on Layer 4 traffic
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Hardware
Acceleration
Mode
Result
Full
The hardware acceleration processes all Layer 4 traffic. Layer 4
traffic is not managed through the use of BIG-IP software
features. In this case, Local Traffic Manager treats client-side
and server-side packets as part of the same connection.
Assisted
None
An example of using hardware acceleration in Full mode is when
you want to load balance Layer 4 traffic to two servers, using the
Round Robin load balancing method, with no session persistence
or iRules.
Local Traffic Manager load balances all SYN packets, while the
hardware acceleration assists with the remaining packets,
including the tearing down of connections.
The hardware acceleration does not process any Layer 4 traffic.
Instead, the BIG-IP application manages all Layer 4 traffic.
The Fast HTTP profile type
The Fast HTTP profile is a configuration tool designed to speed up certain types of HTTP
connections. This profile combines selected features from the TCP, HTTP, and
OneConnect profiles into a single profile that is optimized for the best possible network
performance. When you associate this profile with a virtual server, the virtual server
processes traffic packet-by-packet, and at a significantly higher speed.
You might consider using a Fast HTTP profile when:





You do not need features such as remote server authentication, SSL traffic
management, and TCP optimizations, nor HTTP features such as data
compression, pipelining, and RAM Cache.
You do not need to maintain source IP addresses.
You want to reduce the number of connections that are opened to the
destination servers.
The destination servers support connection persistence, that is, HTTP/1.1, or
HTTP/1.0 with Keep-Alive headers. Note that IIS servers support connection
persistence by default.
You need basic iRule support only (such as limited Layer 4 support and limited
HTTP header operations). For example, you can use the iRule events
CLIENT_ACCEPTED, SERVER_CONNECTED, and HTTP_REQUEST.
A significant benefit of using a Fast HTTP profile is the way in which the profile supports
connection persistence. Using a Fast HTTP profile ensures that for client requests, Local
Traffic Manager can transform or add an HTTP Connection header to keep connections
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open. Using the profile also ensures that Local Traffic Manager pools any open serverside connections. This support for connection persistence can greatly reduce the load
on destination servers by removing much of the overhead caused by the opening and
closing of connections.
Note: The Fast HTTP profile is incompatible with all other profile types. Also, you cannot use
this profile type in conjunction with VLAN groups, or with the IPv6 address format.
You can use the default fasthttp profile as is, or create a custom Fast HTTP profile. The
following table lists and describes the settings of the Fast HTTP profile.
Settings of a Fast HTTP profile
Setting
Description
Name
Specifies a unique name for the profile.
Parent Profile
Specifies the profile that you want to use as the parent
profile. Your new profile inherits all non-custom
settings and values from the parent profile specified.
Reset on
Timeout
Idle Timeout
Maximum
Segment Size
Override
Client Close
Timeout
Server Close
Timeout
Specifies, when checked (enabled), that the system
sends a TCP RESET packet when a connection times
out, and deletes the connection.
This setting specifies the number of seconds that a
connection is idle before the connection flow is eligible
for deletion because it has no traffic. Possible values
are: Specify, Immediate, and Indefinite. For
background information on setting idle timeout values,
see Chapter 1, Introducing BIG-IP Local Traffic
Manager.
Specifies a maximum segment size (MSS) override for
server-side connections. The default setting is 0,
which corresponds to an MSS of 1460. To override
this size, you can specify any integer between 536 and
1460.
Specifies the number of seconds after which the
system closes a client connection, when the system
either receives a client FIN packet or sends a FIN
packet to the client. This setting overrides the Idle
Timeout setting. Possible values are: Specify,
Immediate, and Indefinite. For more information, see
the online help.
Specifies the number of seconds after which the
system closes a client connection, when the system
either receives a server FIN packet or sends a FIN
packet to the server. This setting overrides the Idle
Timeout setting. Possible values are: Specify,
Immediate, and Indefinite. For more information, see
the online help.
Default
Value
No default
value
fasthttp
Enabled
(Checked)
300
0
5
5
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Unclean
Shutdown
Force HTTP
1.0 Response
Maximum Pool
Size
Minimum Pool
Size
Ramp-Up
Increment
Maximum
Reuse
Idle Timeout
Override
Replenish
Parse
Requests
Maximum
Header Size
Maximum
Requests
Insert
XForwarded
For
Specifies how the system handles closing connections.
Possible values are: Disabled, Enabled, and Fast.
For more information, see the online help.
Specifies, when checked (enabled), that the server
sends responses to clients in the HTTP/1.0 format.
This effectively disables client chunking and pipelining.
Disabled
Disabled
(Cleared)
2048
Specifies the maximum number of connections a load
balancing pool can accept. A setting of 0 specifies that
there is no maximum; that is, a pool can accept an
unlimited number of connections.
Specifies the minimum number of connections that a
load balancing pool can accept. A setting of 0
specifies that there is no minimum.
Specifies the increment in which the system makes
additional connections available, when all available
connections are in use.
Specifies the maximum number of times that the
system can re-use a current connection.
Specifies the number of seconds after which a serverside connection in a pool is eligible for deletion, when
the connection has no traffic. This setting overrides the
Idle Timeout setting. Possible values are: Specify,
Disabled, and Indefinite. For more information, see
the online help.
Specifies whether the BIG-IP system should maintain a
steady-state maximum number of back-end
connections. If you disable this setting, the system
does not keep a steady-state maximum of connections
to the back end, unless the number of connections to
the pool drops below the value specified in the
Minimum Pool Size setting.
Specifies, when checked (enabled), that the system
parses the HTTP data in the connection stream. Note
that if you are using a Fast HTTP profile for non-HTTP
traffic, you should disable this setting to shield against
dynamic denial-of-service (DDOS) attacks.
Specifies the maximum amount of HTTP header data
that the system buffers before making a load balancing
decision.
Specifies the maximum number of requests that the
system allows for a single client-side connection.
When the specified limit is reached, the final response
contains a Connection: close header is followed by
the closing of the connection. The default setting of 0
means that the system allows an infinite number of
requests per client-side connection.
Specifies whether the system inserts the XForwarded
For: header in an HTTP request with the client IP
address, to use with connection pooling. Possible
settings are Enabled and Disabled. For more
information, see the online help.
0
4
0
Disabled
Enabled
(Checked)
Enabled
(Checked)
32768
0
Disabled
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Request
Header Insert
Specifies a string that the system inserts as a header in
an HTTP request. If the header exists already, the
system does not replace it.
No default
value
The HTTP Class profile type
An HTTP Class profile is a configuration tool that you can use to classify HTTP traffic.
When you classify traffic, you forward traffic to a destination based on an examination
of traffic headers or content. Use of an HTTP Class profile is an efficient way for Local
Traffic Manager to classify traffic based on criteria that you specify. Although you can
perform these same traffic-classification functions using the iRules feature, using an
HTTP Class profile simplifies this process.
The destination you specify can be either a load balancing pool or a URL. To classify
HTTP traffic, you configure an HTTP Class profile to specify strings that match a list type.
The list types that you can use for string matching are:




Host names
URIs
Headers
Cookies
The string that you can match to one of these lists can be either a pattern string or a
regular expression.
Once Local Traffic Manager matches the string to the corresponding list type, the
system can send the traffic to a pool that you specify. Alternatively, you can create an
HTTP Class profile that forwards a client request from the targeted HTTP virtual server
to an HTTPS virtual server instead of to a pool.
The following table lists and describes the settings of an HTTP Class profile.
Settings of an HTTP Class profile
Setting
Description
Name
Specifies a unique name for the profile.
Parent Profile
Specifies the profile that you want to use as the parent
profile. Your new profile inherits all non-custom settings
Default
Value
No
default
value
httpclass
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Application
Security
WebAccelerator
Hosts
Host List
URI Paths
URI List
Headers
Header List
and values from the parent profile specified.
Specifies that you want a virtual server to forward traffic
to the Application Security ManagerTM application. In this
case, the HTTP Class profile is the equivalent of an
Application Security Manager application security class.
This setting appears only when Application Security
Manager is licensed on the BIG-IP system.
Specifies that you want a virtual server to forward traffic
to the WebAcceleratorTM application. This setting
appears only when WebAccelerator is licensed on the
BIG-IP system.
Specifies whether the host names used as criteria for
routing HTTP requests constitute all hosts or individual
hosts that you specify. A value of Match All directs the
system to forward HTTP requests from all hosts. A value
of Match Only directs the system to forward HTTP
requests based on only those hosts you specify.
Specifies individual host names to be used as criteria for
routing HTTP requests. Using the Entry Type list, you
must also identify each host name as either a pattern
string or a regular expression. This setting appears only
when the value of Hosts is Match Only.
Note: When you use pattern strings, this list type is casesensitive. For more information, see The HTTP Class
profile type.
Specifies whether the URIs used as criteria for routing
HTTP requests constitute all URIs or individual URIs that
you specify. A value of Match All directs the system to
forward HTTP requests from all URIs. A value of Match
Only directs the system to forward HTTP requests based
on only those URIs you specify.
Specifies individual URI paths to be used as criteria for
routing HTTP requests. Using the Entry Type list, you
must also identify each URI as either a pattern string or a
regular expression. This setting appears only when the
value of URI Paths is Match Only.
Note: When you use pattern strings, this list type is casesensitive. For more information, see The HTTP Class
profile type.
Specifies whether the headers and their values, used as
criteria for routing HTTP requests constitute all headers
or individual headers that you specify. A value of Match
All directs the system to forward HTTP requests based
on all headers. A value of Match Only directs the
system to forward HTTP requests based on only those
headers you specify.
Specifies individual headers and their values that the
BIG-IP system uses as criteria for routing HTTP
requests. Using the Entry Type list, you must also
identify each header as either a pattern string or a regular
expression. This setting appears only when the value of
Headers is Match Only.
Disabled
(Cleared)
Disabled
(Cleared)
Match All
No
default
value
Match All
No
default
value
Match All
No
default
value
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Cookies
Cookie List
Send To
Pool
Redirect To
Location
Rewrite URI
Note: When you use pattern strings, this list type is casesensitive. For more information, see The HTTP Class
profile type.
Specifies whether cookies used as criteria for routing
those requests constitute all cookies or individual cookies
that you specify. A value of Match All directs the system
to forward HTTP requests based on all cookies. A value
of Match Only directs the system to forward HTTP
requests based on only those cookies you specify.
Specifies individual cookies to be used as criteria for
routing HTTP requests. Using the Entry Type list, you
must also identify each cookie as either a pattern string
or a regular expression. This setting appears only when
the value of Cookies is Match Only.
Note: When you use pattern strings, this list type is casesensitive. For more information, see The HTTP Class
profile type.
Specifies the destination for HTTP traffic. Possible
values are None, Pool, or Redirect To.
Specifies the name of the pool to which you want to send
classified traffic. This setting appears only when the
value of the Send To setting is Pool.
Specifies the URI to which the system should send the
traffic. You use this setting when you want the profile to
redirect the client request from an HTTP virtual server to
an HTTPS virtual server, instead of to a pool. For
example, you can create an HTTP virtual server with the
URL http://siterequest/, to listen on port 80. You can
then assign an HTTP Class profile to the virtual server, to
redirect client requests to the HTTPS virtual server,
https://siterequest/. Note that the string you specify can
be a Tcl expression, such as
https://[HTTP::host][HTTP::uri].
Specifies the Tcl expression that the system uses to
rewrite the request URI that is forwarded to the server
without sending an HTTP redirect to the client. Note that
if you use static text for this setting instead of a Tcl
expression, the system maps the specified URI for every
incoming request. Also, you cannot use this setting if the
value of the Send To setting is Redirect To.
Match All
No
default
value
None
None
No
default
value
No
default
value
The TCP profile type
TCP profiles are configuration tools that help you to manage TCP network traffic. Many
of the configuration settings of TCP profiles are standard SYSCTL types of settings, while
others are unique to Local Traffic Manager.
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TCP profiles are important because they are required for implementing certain types of
other profiles. For example, by implementing TCP, HTTP, and OneConnect profiles,
along with a persistence profile and a remote authentication profile, you can take
advantage of these traffic management features:









Content spooling, to reduce server load
OneConnect, to pool server-side connections
Layer 7 session persistence, such as hash or cookie persistence
iRules for managing HTTP traffic
HTTP RAM Cache
HTTP data compression
HTTP pipelining
Application authentication using a remote server
Rewriting of HTTP redirections
Local Traffic Manager includes three specific TCP profiles:

tcp
This is the default TCP profile.

tcp-lan-optimized
The tcp-lan-optimized profile is a TCP-type profile. This profile is effectively a
custom profile that Local Traffic Manager has already created for you, derived
from the default tcp profile. This profile is useful for environments where a link
has higher bandwidth and/or lower latency when paired with a slower link.

tcp-wan-optimized
The tcp-wan-optimized profile is a TCP-type profile. This profile is effectively a
custom profile that Local Traffic Manager has already created for you, derived
from the default tcp profile. This profile is useful for environments where a link
has lower bandwidth and/or higher latency when paired with a faster link.
The following table lists and describes the settings of the default tcp profile.
Settings of a TCP profile
Setting
Description
Name
Specifies a unique name for the profile.
Parent Profile
Specifies the profile that you want to use as the
parent profile. Your new profile inherits all non-
Default
Value
No default
value
tcp
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Reset on Timeout
Time Wait Recycle
Delayed ACKs
Proxy Maximum
Segment
Proxy Options
Proxy Buffer Low
Proxy Buffer High
Idle Timeout
Zero Window Timeout
Time Wait
FIN Wait
Close Wait
Send Buffer
custom settings and values from the parent profile
specified.
If this setting is enabled and a TCP connection
exceeds the timeout value for idle connections,
sends a reset in addition to deleting the
connection.
Recycles the connection when a SYN packet is
received in a TIME-WAIT state.
If this setting is enabled, allows coalescing of
multiple acknowledgement (ACK) responses.
Advertises the same maximum segment to the
server as was negotiated with the client.
Advertises an option (such as timestamps) to the
server only if it was negotiated with the client.
Specifies the proxy buffer level at which the
receive window was opened.
Specifies the proxy buffer level at which the
receive window was closed.
Specifies the number of seconds that a connection
is idle before the connection is eligible for deletion.
For background information on setting idle timeout
values, see Chapter 1, Introducing BIG-IP Local
Traffic Manager.
Specifies the length of time, in milliseconds, that
the TCP connection can receive zero-length
window probes before the system closes the
connection. The timer starts when an effective
window size becomes zero, and stops when the
window size becomes greater than zero. If the
timer elapses, the connection is terminated. This
setting is useful for handling slow clients with
small buffers, such as cell phones.
Possible values are:
Specify: Specifies a number of milliseconds that
the TCP connection can receive zero-length
window probes before the system closes the
connection.
Indefinite: Specifies that the system does not
delete TCP connections based on zero-length
window.
Specifies the number of milliseconds that a
connection is in a TIME-WAIT state before
entering the CLOSED state.
Specifies the number of seconds that a connection
is in the FIN-WAIT or CLOSING state before
quitting. A value of 0 represents a term of forever
(or until the metrics of the FIN state).
Specifies the number of seconds that a connection
remains in a LAST-ACK state before quitting. A
value of 0 represents a term of forever (or until the
metrics of the FIN state).
Causes the BIG-IP system to send the buffer size,
Enabled
(Checked)
Enabled
(Checked)
Enabled
(Checked)
Disabled
(Cleared)
Disabled
(Cleared)
4096
16384
300
20000
2000
5
5
32768
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Receive Window
Keep Alive Interval
Maximum SYN
Retransmissions
Maximum Segment
Retransmissions
IP ToS
Link QoS
Selective ACKs
Extended Congestion
Notification
Extensions for High
Performance (RFC
1323)
Limited Transmit
Recovery
which is specified in bytes.
Causes the BIG-IP system to receive the window
size, which is specified in bytes.
Causes the BIG-IP system to keep alive the probe
interval, which is specified in seconds.
Specifies the maximum number of retransmissions
of SYN segments that the BIG-IP system allows.
Specifies the maximum number of retransmissions
of data segments that the BIG-IP system allows.
Specifies the Type of Service level that the BIG-IP
system assigns to TCP packets when sending
them to clients.
Specifies the Quality of Service level that the BIGIP system assigns to TCP packets when sending
them to clients.
Specifies, when checked (enabled), that the
system processes data using selective ACKs
whenever possible, to improve system
performance. Enabling this setting improves
packet flow in a lossy network because the system
can acknowledge successfully received packets
out of order. This is a negotiated option and is
automatically disabled if not supported by a peer.
Note: F5 recommends that you use the default
value.
Specifies, when checked (enabled), that the
system uses the TCP flags CWR (congestion
window reduction) and ECE (ECN-Echo) to notify
its peer of congestion and congestion countermeasures.
Note: F5 recommends that you use the default
setting. When enabled, this setting can interfere
with overall congestion calculations. The setting
also allows for potential security issues, whereby
an intermediate device can stimulate poor
performance by spoofing CWR packets.
Specifies, when checked (enabled), that the
system uses the timestamp and window scaling
extensions for TCP (as specified in RFC 1323) to
enhance high-speed network performance. These
options are used to help calculate the round trip
time, as well as the available resources on a peer.
They are fundamentally linked with congestion
control. Also, these options are normally
negotiated, and you should not need to disable
them unless a network device or peer does not
implement them correctly.
Specifies, when checked (enabled), that the
system uses limited transmit recovery revisions for
fast retransmits (as specified in RFC 3042), to
reduce the recovery time for connections on a
32768
1800
3
8
0
0
Enabled
(Checked)
Disabled
(Cleared)
Enabled
(Checked)
Enabled
(Checked)
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Slow Start
lossy network. Enabling this setting allows TCP to
temporarily stretch the congestion window when
first receiving a duplicate ACK packet. This in turn
allows for faster retransmissions and a quicker
recovery from the small congestion window. With
this setting enabled, the aggressive transmit
behavior is limited to the recovery period.
Specifies, when checked (enabled), that the
system uses larger initial window sizes (as
specified in RFC 3390) to help reduce round trip
times. The setting ramps up the amount of data
transmitted to a peer over a period of time.
Enabling this setting avoids sudden and excessive
congestion on the link. Also, the congestion
metrics cache might provide historical data about
the peer, allowing the slow start to be jump
started.
If you disable this setting, the system initializes the
congestion window to the maximum window scale
and attempts to transmit as much data as possible
until congestion occurs. Consequently, in
networks with unlimited bandwidth (such as
directly-connected local peers), more data can
initially be transmitted.
Deferred Accept
Verified Accept
Specifies, when checked (enabled), that the
system defers allocation of the connection chain
context until the system has received the payload
from the client. Enabling this setting is useful in
dealing with 3-way handshake denial-of-service
attacks.
When enabled, verifies that a server is available to
accept the connection (by actually sending the
server a SYN) before responding to the client's
SYN with a SYN-ACK. (Normally, the BIG-IP
system accepts the client's connection before
selecting a server with which to communicate.)
Bandwidth Delay
Specifies, when checked (enabled), that the
system attempts to calculate the optimal
bandwidth to use to the client, based on
throughput and round-trip time, without exceeding
the available bandwidth.
Nagles Algorithm
Specifies, when checked (enabled), that the
system applies Nagle's algorithm to reduce the
number of short segments on the network. When
the system receives packets that are less than the
maximum segment size (MSS), the packets are
coalesced until the peer has sent the ACK packet
for the previous segment. This helps to reduce
congestion by creating fewer packets on the
Enabled
(Checked)
Disabled
(Cleared)
Disabled
(Cleared)
Enabled
(Checked)
Enabled
(Checked)
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Acknowledge on
Push
MD5 Signature
MD5 Signature
Passphrase
Congestion Control
Congestion Metrics
network.
Note that enabling this setting for interactive
protocols such as Telnet might cause degradation
on high-latency networks.
Specifies, when enabled, significantly improved
performance to Windows® and Mac OS peers who
are writing out on a very small send buffer.
Specifies, when enabled, to use RFC2385 TCPMD5 signatures to protect TCP traffic against
intermediate tampering.
Specifies, when enabled, a plaintext passphrase
which may be between 1 and 80 characters in
length, and is used in a shared-secret scheme to
implement the spoof-prevention parts of
RFC2385.
Specifies the congestion control mechanism that
the BIG-IP system is to use. Possible values are:
None--No congestion control algorithm
implemented. With you choose this value, any
congestion will result in lost packets and
potentially long recovery stalls during large data
transfers.
High Speed--A more aggressive, loss-based
algorithm. This algorithm improves on the
behavior of the New Reno algorithm by
progressively switching from the New Reno
algorithm to the Scalable algorithm, based on the
size of the congestion window. This allows the
algorithm to make more aggressive changes when
the window is small and make more conservative
changes when the window is already large.
New Reno--A modification to the Reno algorithm
that responds to partial acknowledgements when
selective acknowledgements (SACKs) are
unavailable. This algorithm sends missing data
and exits the recovery period more aggressively
than does the Reno algorithm. The New Reno
algorithm produces reasonable results for scaling
the window in mixed environments.
Reno--An implementation of the TCP Fast
Recovery algorithm, based on the implementation
in the BSD Reno release. During the slow-start
period, this algorithm initially increases the
congestion window exponentially.
Scalable--A TCP algorithm modification that adds
a scalable, delay-based and loss-based
component into the Reno algorithm. This
algorithm improves on the behavior of the New
Reno algorithm. The algorithm is more tolerant of
partial losses; it cuts back and increases the
congestion window more conservatively.
Specifies, when checked (enabled), that the
Disabled
(Cleared)
Disabled
(Cleared)
No default
value
High
Speed
Enabled
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Cache
Appropriate Byte
Counting
(RFC 3465)
D-SACK (RFC 2883)
Packet Lost Ignore
Rate
Packet Lost Ignore
Burst
Initial Congestion
Window Size
Initial Receive
Window Size
Initial Retransmission
Timeout Base
Multiplier for SYN
Retransmission
system uses a cache for storing congestion
metrics. Subsequently, because these metrics are
already known and cached, the initial slow-start
ramp for previously-encountered peers improves.
Increases the congestion window by basing the
increase amount on the number of previously
unacknowledged bytes that each ACK covers.
Note: F5 recommends that you use the default
setting. When this setting is disabled, in situations
with lost ACK packets, the congestion window
remains small for a longer period of time.
Specifies the use of the Selective ACKs (SACK)
option to acknowledge duplicate segments. If a
peer does not send duplicate segments, the
system disables SACK processing altogether.
Note that when enabled, this setting requires more
processing, to always populate the SACK with all
duplicate segments.
Specifies the threshold of packets lost per million
at which the system performs congestion control.
Valid values range from 0 to 1,000,000. The
default is 0, meaning the system performs
congestion control if any packet loss occurs. If
you set the ignore rate to 10 and packet loss for a
TCP connection is greater than 10 per million,
congestion control occurs.
Specifies the probability of performing congestion
control when multiple packets are lost, even if the
value of the Packet Lost Ignore Rate setting
was not exceeded. Valid values range from 0 to
4,294,967,295. A value of 0 means that the
system performs congestion control if any packets
are lost. Higher values decrease the chance of
performing congestion control.
Specifies the initial congestion window size for
connections to this destination. Actual window
size is this value multiplied by the MSS (Maximum
Segment Size) for the same connection. The
default is 0 (zero), meaning that the system uses
the values specified in RFC2414. Valid values
range from 0 to 16.
Specifies the initial receive window size for
connections to this destination. Actual window
size is this value multiplied by the MSS (Maximum
Segment Size) for the same connection. The
default is 0 (zero), meaning that the system uses
the Slow Start value. Valid values range from 0 to
16.
Specifies the initial RTO (Retransmission
TimeOut) base multiplier for SYN retransmissions.
The default is 0 (zero). This value is modified by
the exponential backoff table, which selects the
(Checked)
Enabled
(Checked)
Disabled
(Cleared)
0
0
0
0
0
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Delay Window
Control
interval for subsequent retransmissions.
Specifies that the system will use an estimate of
queueing delay as a measure of congestion to
control, in addition to the normal loss-based
control, the amount of data sent.
Disabled
The UDP profile type
The UDP profile is a configuration tool for managing UDP network traffic.
Because the BIG-IP system supports the OpenSSL implementation of datagram
Transport Layer Security (TLS), you can optionally assign both a UDP and a Client SSL
profile to certain types of virtual servers.
The following table lists and describes the settings of a UDP profile.
Settings of a UDP profile
Setting
Description
Name
This setting specifies a unique name for the profile.
Parent
Profile
This setting specifies the profile that you want to use as
the parent profile. Your new profile inherits all noncustom settings and values from the parent profile
specified.
This setting specifies the number of seconds that a
connection is idle before the connection flow is eligible for
deletion. For background information on setting idle
timeout values, see Chapter 1, Introducing BIG-IP Local
Traffic Manager.
This setting specifies the Type of Service level that the
BIG-IP system assigns to UDP packets when sending
them to clients.
This setting specifies the Quality of Service level that the
BIG-IP system assigns to UDP packets when sending
them to clients.
This setting specifies, when checked (enabled), that the
system load balances UDP traffic packet-by-packet.
This setting specifies, when checked (enabled), that the
system passes datagrams that contain header
information, but no essential data.
Idle
Timeout
IP ToS
Link QoS
Datagram
LB
Allow No
Payload
Default
Value
No default
value
udp
60
0
0
Disabled
(Unchecked)
Disabled
(Unchecked)
The SCTP profile type
Local Traffic Manager includes a profile type that you can use to manage Stream Control
Transmission Protocol (SCTP) traffic. Stream Control Transmission Protocol (SCTP) is a
general-purpose, industry-standard transport protocol, designed for message-oriented
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applications that transport signaling data. The design of SCTP includes appropriate
congestion avoidance behavior, as well as resistance to flooding and masquerade
attacks.
Unlike TCP, SCTP includes the ability to support several streams within a connection.
While a TCP stream refers to a sequence of bytes, an SCTP stream represents a
sequence of messages.
You can use SCTP as the transport protocol for applications that require monitoring and
detection of session loss. For such applications, the SCTP mechanisms to detect session
failure actively monitor the connectivity of a session.
The following table lists and describes the settings of an SCTP profile.
Settings of an SCTP profile
Setting
Description
Name
Specifies a unique name for the profile.
Parent Profile
Specifies the profile that you want to use as the parent
profile. Your new profile inherits all non-custom
settings and values from the parent profile specified.
If this setting is enabled, the system delivers messages
to an upper layer, in order.
If this setting is enabled, the system accepts a partial
amount of application data.
If this setting is enabled, SCTP instances emulate TCP
closing. After receiving a SHUTDOWN message from
an upper-layer user process, an SCTP instance
initiates a graceful shutdown, by sending a
SHUTDOWN chunk.
If this setting is enabled and an SCTP connection
exceeds the timeout value for idle connections, the
system sends a reset in addition to deleting the
connection.
Specifies the number of outbound streams that you
want the chunk to request.
Specifies the number of inbound streams that you want
the chunk to request.
Causes the BIG-IP system to send the buffer size, in
bytes.
Specifies the number of bytes that a sender can
transmit without receiving an acknowledgment (ACK).
Specifies the number of transmit chunks allowed in
buffer.
Specifies the number of receive chunks allowed in
buffer.
Specifies the valid duration of a cookie, in seconds.
Receive
Ordered
Send Partial
TCP Shutdown
Reset on
Timeout
Out Streams
In Streams
Send Buffer
Receive
Window
Transmit
Chunks
Receive Chunks
Cookie
Expiration
Default
Value
No default
value
tcp
Enabled
(Checked)
Enabled
(Checked)
Enabled
(Checked)
Enabled
(Checked)
2
2
65536
65535
256
256
60
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Maximum Initial
Retransmit Limit
Maximum
Association
Retransmit Limit
Proxy Buffer
Low
Proxy Buffer
High
Idle Timeout
Heartbeat
Interval
IP ToS to Peer
Link QoS to
Peer
Secret
Specifies the maximum number of times that the
system attempts to establish a connection.
Specifies the maximum number of times that the
system attempts to send data.
4
Specifies the proxy buffer level at which the system
opens the receive window.
Specifies the proxy buffer level at which the system
closes the receive window.
Specifies the number of seconds that a connection is
idle before the connection is eligible for deletion. For
background information on setting idle timeout values,
see Chapter 1, Introducing BIG-IP Local Traffic
Manager.
Specifies the number of seconds to wait before
sending a heartbeat chunk.
Specifies the Type of Service level that the BIG-IP
system assigns to SCTP packets when sending them
to a client.
Specifies the Quality of Service level that the BIG-IP
system assigns to SCTP packets when sending them
to a client.
Specifies the internal secret string used to calculate the
key-hash method authentication code (HMAC) for
cookie verification.
4096
8
16384
300
30
0
0
default
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3.02 - Explain the use cases for the fast protocols (e.g. fastL4, fastHTTP)
Link to Online Topic Content
Fast L4
The purpose of a Fast L4 profile is to help you manage Layer 4 traffic more efficiently.
When you assign a Fast L4 profile to a virtual server, the Packet Velocity® ASIC (PVA)
hardware acceleration within the BIG-IP system can process some or all of the Layer 4
traffic passing through the system. By offloading Layer 4 processing to the PVA
hardware acceleration, the BIG-IP system can increase performance and throughput for
basic routing functions (Layer 4) and application switching (Layer 7).
You can use a Fast L4 profile with these types of virtual servers: Performance (Layer 4),
Forwarding (Layer 2), and Forwarding (IP).
This profile will typically be used when there is no need to process the traffic above
Layer 4.
Fast HTTP
The Fast HTTP profile is a configuration tool designed to speed up certain types of HTTP
connections. This profile combines selected features from the TCP, HTTP, and
OneConnect profiles into a single profile that is optimized for the best possible network
performance. When you associate this profile with a virtual server, the virtual server
processes traffic packet-by-packet, and at a significantly higher speed.
You might consider using a Fast HTTP profile when:





You do not need features such as remote server authentication, SSL traffic
management, and TCP optimizations, nor HTTP features such as data
compression, pipelining, and RAM Cache.
You do not need to maintain source IP addresses.
You want to reduce the number of connections that are opened to the
destination servers.
The destination servers support connection persistence, that is, HTTP/1.1, or
HTTP/1.0 with Keep-Alive headers. Note that IIS servers support connection
persistence by default.
You need basic iRule support only (such as limited Layer 4 support and limited
HTTP header operations). For example, you can use the iRule events
CLIENT_ACCEPTED, SERVER_CONNECTED, and HTTP_REQUEST.
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A significant benefit of using a Fast HTTP profile is the way in which the profile supports
connection persistence. Using a Fast HTTP profile ensures that for client requests, Local
Traffic Manager can transform or add an HTTP Connection header to keep connections
open. Using the profile also ensures that Local Traffic Manager pools any open serverside connections. This support for connection persistence can greatly reduce the load
on destination servers by removing much of the overhead caused by the opening and
closing of connections.
Note: The Fast HTTP profile is incompatible with all other profile types. Also, you cannot use
this profile type in conjunction with VLAN groups, or with the IPv6 address format.
When writing iRules, you can specify a number of events and commands that the Fast
HTTP profile supports.
You can use the default fasthttp profile as is, or create a custom Fast HTTP profile.
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3.02 - Explain the persistence overrides
Link to Online Topic Content
Persistence Overrides
Persistence is the nemesis of load balancing! When any type of persistence is needed it
overrides the function of load balancing. When persistence is configured, the first
inbound connection is load balanced to the best pool member resource according to the
algorithm and availability status. All following client requests are then directed to the
same pool member throughout the life of a session or during subsequent sessions.
Persistence can even be configured to Override Connection Limits in the profile settings.
This setting says that the system will allow pool member connection limits to be
overridden for persisted clients. Per-virtual connection limits remain hard limits and are
not overridden.
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3.02 - Describe the use of HTTP classes and profiles
Link to Online Topic Content
HTTP Classes
In BIG-IP 9.4.x through 11.3.0, the HTTP Class profile provides a way to classify HTTP
traffic and perform an action, such as sending the traffic to a load-balancing pool,
rewriting the URI, or forwarding traffic to a selected module, such as ASM.
Note: Starting in BIG-IP 11.4.0, the HTTP Class profile is replaced by the Local Traffic Policies
feature.
An HTTP Class profile allows you to sort selected HTTP traffic and perform an action
based on the profile configuration. For example, you can send the traffic to a
destination, such as a load balancing pool or rewrite the URI.
In addition, you can use the HTTP Class profile to forward traffic to a selected module
such as ASM, or WebAccelerator (9.4.x - 10.x).
Beginning in BIG-IP WebAccelerator 11.0.0, web acceleration is enabled through the
Web Acceleration profile.
To classify HTTP traffic, you configure an HTTP Class profile to specify strings that match
a list type. The string that you can match to one of these lists can be either a pattern
string or a regular expression. The list types are case-sensitive for pattern strings. For
example, the system treats the pattern string www.f5.com differently from the pattern
string www.F5.com. You can override this case-sensitivity by using the Linux regexp
command.
F5 recommends using HTTP Class profiles when it is possible to classify HTTP traffic
using simple strings or regex patterns. For more complex operations, you may need to
use an iRule.
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3.02 - Describe the link between iRules and statistics, iRules and stream,
and iRule events and profiles
Link to Online Topic Content
iRules and Statistics
The Statistics profile provides user-defined statistical counters. Each profile contains 32
settings (Field1 through Field32), which define named counters. Using a cl-based iRule
command, you can use the names to manipulate the counters while processing traffic.
For example, you can create a profile named my_stats, which assigns the counters
tot_users, cur_users, and max_users to the profile settings Field1, Field2, and Field3
respectively. You can then write an iRule named track_users, and then assign the
my_stats profile and the track_users iRule to a virtual server named stats-1.
Example of Statistics profile counters used in an iRule
profile stats my_stats {
defaults from stats
field1 tot_users
field2 cur_users
field3 max_users
}
rule track_users {
when CLIENT_ACCEPTED {
STATS::incr my_stats tot_users
STATS::setmax my_stats max_users [STATS::incr my_stats cur_users]
}
}
virtual stats-1 {
destination 10.10.55.66:http
ip protocol tcp
profile http my_stats tcp
pool pool1
rule track_users
}
In this example, the counter tot_users counts the total number of connections, the
counter cur_users counts the current number of connections, and the counter
max_users retains the largest value of the counter cur_users.
Link to Online Topic Content
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iRules and Stream
Using an iRule to apply a Stream profile only when desired traffic is seen, can be a
powerful way to use Stream profiles.
For example, when you want to scrub content; instead of collecting the HTTP response
payloads, the iRule can uses the stream filter to replace the strings inline. This should
be more efficient than buffering the payload with the HTTP::collect command.
Another Example, you may need to only look for a particular string within XML content
and replace it with a different string. The string you are looking for may appear in
multiple locations, not just in the XML content. Using a Stream profile to replace the
string would cause the string to be replaced everywhere in the content not just in the
XML content. Using an iRule to run when it sees XML content and then apply the
stream will give you the power you need to solve the issue.
Link to Online Topic Content
iRules and Profiles
When you are writing an iRule, you might want that iRule to recognize the value of a
particular profile setting so that it can make a more-informed traffic management
decision. Fortunately, the iRules feature includes a command that is specifically
designed to read the value of profile settings that you specify within the iRule.
Not only can iRules read the values of profile settings, but they can also override values
for certain settings. This means that you can apply configuration values to individual
connections that differ from the values Local Traffic Manager applies to most
connections passing through a virtual server.
The Profile Command
The iRules feature includes a command called PROFILE. When you specify the PROFILE
command in an iRule and name a profile type and setting, the iRule reads the value of
that particular profile setting. To do this, the iRule finds the named profile type that is
assigned to the virtual server and reads the value of the setting that you specified in the
PROFILE command sequence. The iRule can then use this information to manage traffic.
For example, you can specify the command PROFILE::tcp idle_timeout within your iRule.
Local Traffic Manager then finds the TCP profile that is assigned to the virtual server (for
example, my_tcp) and queries for the value that you assigned to the Idle Timeout
setting.
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Note: If an iRule references a profile, Local Traffic Manager processes this type of iRule last,
regardless of its order in the list of iRules assigned to a virtual server.
Commands That Override Profile Settings
Some of the iRule commands for querying and manipulating header and content data
have equivalent settings within various profiles. When you use those commands in an
iRule, and an event triggers that iRule, Local Traffic Manager overrides the values of
those profile settings, using the value specified within the iRule instead.
For example, an HTTP profile might specify a certain buffer size to use for compressing
HTTP data, but you might want to specify a different buffer size for a particular type of
HTTP connection. In this case, you can include the command
HTTP::compress_buffer_size in your iRule, specifying a different value than the value in
the profile.
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3.02 - Describe the link between iRules and persistence
Link to Online Topic Content
iRules and Persistence
You can assign a persistence profile from within an iRule as you can most profiles. But
there is a persistence method that specifically relies on an iRule to fuction. This type of
persistence is known as Universal Persistence.
Universal Persistence
Included in Local Traffic Managers Universal Inspection Engine (UIE) is a set of functions
that you can specify within BIG-IP system iRules to direct traffic in more granular ways.
Using these iRule functions, you can write expressions that direct traffic based on
content data, or direct traffic to a specific member of a pool.
Universal persistence takes this iRules feature one step further, by allowing you to use
the iRule persist uie command to implement persistence for sessions based on content
data, or based on connections to a specific member of a pool. Universal persistence
does this by defining some sequence of bytes to use as a session identifier.
To use iRule expressions for persistence, a universal persistence profile includes a
setting that specifies the name of the iRule containing the expression.
Sample iRule for universal persistence
rule my_persist_irule {
when HTTP_REQUEST { persist uie [HTTP::header myheader] }
}
Unlike hash persistence, which uses a hash of the data as the persistence key, universal
persistence uses the data itself as the persistence key.
Note: F5 Networks recommends that you configure a OneConnect profile in addition to the
Universal profile, to ensure that Local Traffic Manager load balances HTTP requests
correctly.
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3.02 - Describe hashing persistence methods
Link to Online Topic Content
Hash persistence
Hash persistence allows you to create a persistence hash based on an existing iRule that
uses the persist iRule command. Using hash persistence is the same as using universal
persistence, except that with hash persistence, the resulting persistence key is a hash of
the data, rather than the data itself.
Sample iRule for hash persistence
rule my_persist_irule {
when HTTP_REQUEST { persist hash [HTTP::header myheader] }
}
Note that if you use hash persistence and Local Traffic Manager cannot find an entry in
the persistence table for a connection, and the system has not yet chosen a pool
member due to fallback persistence, then the system uses the hash value, rather than
the specified load balancing method, to select the pool member.
For example, if the persistence table contains no entry for the hash value 2356372769,
and the number of active nodes in the pool remains the same, then a session with that
hash value for persistence is always persisted to node 10.10.10.190 (assuming that the
node is active).
Cookie Hash Method
If you specify the Cookie Hash method, the hash method consistently maps a cookie
value to a specific node. When the client returns to the site, Local Traffic Manager uses
the cookie information to return the client to a given node. With this method, the web
server must generate the cookie; Local Traffic Manager does not create the cookie
automatically as it does when you use the HTTP Cookie Insert method.
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3.02 - Describe the cookie persistence options
Link to Online Topic Content
Cookie Persistence
You can set up Local Traffic Manager to use HTTP cookie persistence. Cookie
persistence uses an HTTP cookie stored on a client’s computer to allow the client to
reconnect to the same pool member previously visited at a web site.
There are four methods of cookie persistence available:




HTTP Cookie Insert method
HTTP Cookie Rewrite method
HTTP Cookie Passive method
Cookie Hash method
The method you choose to use affects how Local Traffic Manager returns the cookie
when returning the cookie to the client.
HTTP Cookie Insert method
If you specify HTTP Cookie Insert method within the profile, the information about the
server to which the client connects is inserted in the header of the HTTP response from
the server as a cookie. The cookie is named BIGipServer<pool_name>, and it includes
the address and port of the server handling the connection. The expiration date for the
cookie is set based on the timeout configured on the BIG-IP system. HTTP Cookie Insert
is the default value for the Cookie Method setting.
Tip: You can assign this type of profile to a Performance (HTTP) type of virtual server.
HTTP Cookie Rewrite method
If you specify HTTP Cookie Rewrite method, Local Traffic Manager intercepts a SetCookie header, named BIGipCookie, sent from the server to the client, and overwrites
the name and value of the cookie. The new cookie is named BIGipServer<pool_name>
and it includes the address and port of the server handling the connection.
Important: We recommend that you use this method instead of the HTTP Cookie Passive
method whenever possible.
The HTTP Cookie Rewrite method requires you to set up the cookie created by the
server. For the HTTP Cookie Rewrite method to succeed, there needs to be a blank
cookie coming from the web server for Local Traffic Manager to rewrite. With Apache
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variants, the cookie can be added to every web page header by adding the following
entry to the httpd.conf file:
Header add Set-Cookie BIGipCookie=0000000000000000000000000...
(The cookie must contain a total of 120 zeros.)
Note: For backward compatibility, the blank cookie can contain only 75 zeros. However,
cookies of this size do not allow you to use iRules and persistence together.
HTTP Cookie Passive method
If you specify the HTTP Cookie Passive method, Local Traffic Manager does not insert or
search for blank Set-Cookie headers in the response from the server. This method does
not try to set up the cookie. With this method, the server provides the cookie,
formatted with the correct server information and timeout.
Important: We recommend that you use the HTTP Cookie Rewrite method instead of
the HTTP Cookie Passive method whenever possible.
For the HTTP Cookie Passive method to succeed, there needs to be a cookie coming
from the web server with the appropriate server information in the cookie. Using the
Configuration utility, you generate a template for the cookie string, with encoding
automatically added, and then edit the template to create the actual cookie.
For example, the following string is a generated cookie template with the encoding
automatically added, where [pool name] is the name of the pool that contains the
server, 336260299 is the encoded server address, and 20480 is the encoded port:
Set-Cookie:BIGipServer[poolname]=336268299.20480.0000; expires=Sat, 01-Jan-2002
00:00:00 GMT; path=/
Cookie Hash method
If you specify the Cookie Hash method, the hash method consistently maps a cookie
value to a specific node. When the client returns to the site, Local Traffic Manager uses
the cookie information to return the client to a given node. With this method, the web
server must generate the cookie; Local Traffic Manager does not create the cookie
automatically as it does when you use the HTTP Cookie Insert method.
Cookie profile settings
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To implement cookie persistence, you can either use the default cookie profile, or
create a custom profile.
Settings of a Cookie persistence profile
Setting
Description
Default Value
Name
No default value
Persistence
Type
Cookie
Method
Cookie Name
Expiration
Hash Offset
Hash Length
Timeout
Mirror
Persistence
Match Across
Services
Match Across
Virtual
Servers
Match Across
Pools
Override
Connection
Limit
Specifies a unique name for the profile. This
setting is required.
Specifies the type of persistence. This setting is
required.
Specifies the type of cookie processing that the
BIG-IP system is to use. For more information,
see HTTP Cookie Insert method, following.
Specifies the name of the cookie that the BIG-IP
system should look for or insert.
Cookie
HTTP Cookie Insert
This value is
autogenerated
based on the pool
name.
Sets the expiration time of the cookie. Applies to Enabled (Checked)
the HTTP Cookie Insert and HTTP Cookie
Rewrite methods only. When using the default
(checked), the system uses the expiration time
specified in the session cookie.
With respect to Cookie persistence, this setting
0
applies to the Cookie Hash method only.
With respect to Cookie persistence, this setting
0
applies to the Cookie Hash method only.
This setting applies to the Cookie Hash method 180
only. The setting specifies the duration, in
seconds, of a persistence entry.
Specifies, when enabled (checked), that if the
Disabled (Cleared)
active unit goes into the standby mode, the
system mirrors any persistence records to its
peer. With respect to Cookie profiles, this
setting applies to the Cookie Hash method only.
Specifies that all persistent connections from a
Disabled (Cleared)
client IP address that go to the same virtual IP
address also go to the same node. With respect
to Cookie profiles, this setting applies to the
Cookie Hash method only.
Specifies that all persistent connections from the Disabled (Cleared)
same client IP address go to the same node.
With respect to Cookie profiles, this setting
applies to the Cookie Hash method only.
Specifies that the BIG-IP system can use any
Disabled (Cleared)
pool that contains this persistence entry. With
respect to Cookie profiles, this setting applies to
the Cookie Hash method only.
Specifies, when checked (enabled), that the
Disabled (Cleared)
system allows you to specify that pool member
connection limits are overridden for persisted
clients. Per-virtual connection limits remain hard
limits and are not overridden.
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3.02 - Determine which profiles are appropriate for a given application
Link to Online Topic Content
Profiles
The BIG-IP LTM system can manage application-specific network traffic in a variety of
ways, depending on the protocols and services being used. For example, you can
configure the LTM system to compress HTTP response data, or you can configure the
system to authenticate SSL client certificates before passing requests on to a target
server.
For each type of traffic that you want to manage, the LTM system contains configuration
tools that you can use to intelligently control the behavior of that traffic. These tools
are called profiles. A profile is a system-supplied configuration tool that enhances your
capabilities for managing application-specific traffic. More specifically, a profile is an
object that contains user-configurable settings, with default values, for controlling the
behavior of a particular type of network traffic, such as HTTP connections. Using
profiles enhances your control over managing network traffic, and makes trafficmanagement tasks easier and more efficient.
Appropriate Profiles
You can set up a virtual server to process traffic with simply an unmodified client and
server side Protocol Profile and a pool for the destination. And the biggest decision you
had to make was is the traffic TCP, UDP or SCTP based. But when the application you
are working with needs advanced processing up to the application layer you will need a
profile to make that happen.
As an administrator you will need to understand the type of application traffic with
which you are working. So you can choose the matching protocol profiles that will allow
the traffic to be processed correctly. The settings of those profiles will give you the
ability to understand what may need to be done to the traffic as the BIG-IP LTM is
processing it. The processing of the application level traffic is controlled by the
associated application level profiles applied to the virtual server. Even if the processing
you need to do will be completed with an iRule the events in the iRule may only be
allowed if the correct profiles are applied.
So the short of it is, understand what protocols your applications are using and what
functions your applications need to have done and pick those correlating profiles.
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3.02 - Determine when an iRule is preferred over a profile or vice versa
Link to Online Topic Content
iRule vs Profile
It would seem that manipulating packet contents is so easily accomplished by using an
iRule that it is always the way to go. However, the code for TMM profiles is compiled in
the TMM kernel, and has undergone strenuous testing & optimization to be as fast &
reliable as possible, so if you can use a built-in profile option instead of an iRule, it will
be more efficient.
The functions that are built into most profiles are the necessary or most common
functions. If you need to do more than a profile can do for the traffic processing then an
iRule is the way to go.
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3.02 - Explain how to manipulate the packet contents using profiles
Manipulating Packet Contents Using Profiles
There are a few profiles that can manipulate packet contents for their purposes.
Ref: 1, Other Profiles.
The Stream Profile
The stream profile performs a “search and replace” for all occurrences of the string in
the TCP data string, both requests and responses. If you wish to limit substitution to
certain situations, you must define an iRule with appropriate STREAM commands.
When a virtual server has a stream profile, the search and replace operation can be
performed on both client requests (changing requests on the way to the servers) and
server responses (changing responses on the way to the client). The stream profile
performs search and replace on a packet-by-packet basis. While the TCP profile will
adjust the IP header length, the stream profile will not adjust the HTTP Content-Length
header. Also went an HTTP profile is associated with the virtual server, the stream
profile processes the HTTP data portion of the packet, not HTTP headers
Note that list types are case-sensitive for pattern strings. For example, the system
treats the pattern string www.f5.com differently from the pattern string www.F5.com.
You can override this case sensitivity by using the Linux regexp command.
Link to Online Topic Content
The HTTP Profile
The HTTP profile has a setting that will insert an XForwarded-For header into an HTTP
request, to use with connection pooling. This feature adds the IP address of the client
as the value of the XForwarded-For header.
The setting is used to send the original client IP address to the web server so the server
can populate its event logs with the original client IP address when traffic coming to the
server is SNAT’d.
Link to Online Topic Content
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The Cookie Persistence Profile
If you specify HTTP Cookie Insert method within the profile, the information about the
server to which the client connects is inserted in the header of the HTTP response from
the server as a cookie. The cookie is named BIGipServer<pool_name>, and it includes
the address and port of the server handling the connection. The expiration date for the
cookie is set based on the timeout configured on the BIG-IP system. HTTP Cookie Insert
is the default value for the Cookie Method setting.
Each of these profile’s functions or settings could be done within an iRule, but it is
accomplishable without writing any code on the BIG-IP platform using these profiles.
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Objective - 3.03 Determine the effect of traffic flow on LTM
device performance and/or utilization
3.03 - Describe the effect of priority groups on load balancing
Link to Online Topic Content
Effect of priority groups on load balancing
Priority Groups are designed to dynamically allocate additional pool members to the
pool, as resources drop below the minimum active member setting. With priority group
activation configured load balancing algorithms may not seem to behave as expected.
Pool members that are not activated by the priority group will not receive any traffic
until they become active, due to a higher priority group member failure. And as lower
priority groups are brought online they are added to the pool algorithm as net new
resources.
Depending on the algorithm that you are using for load balancing the load across the
pool this can cause issues when a server is being added. For example: If least
connections was the algorithm for the pool and the priority group “at least” setting was
2. If the pool lost members and was down to one remaining, the priority group would
enable the next lowest group of servers. This could cause the new servers that are now
entering the pool with zero layer 4 connections to receive all new connections until
those incoming servers have caught up to the exiting server’s level of layer 4
connections. This may over whelm a server or make the pool seem as if it is not load
balancing the traffic across the servers.
You can use the setting Slow Ramp Time to alleviate the risk of a server being over
whelmed with all of the new connections in this scenario.
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3.03 - Explain the effects of SNAT settings on pools
Link to Online Topic Content
A SNAT is a configuration object (processing all traffic based on source VLAN and origin
address) or is a setting within the configuration of each virtual server (processing all
traffic passing through the virtual server) or a SNAT can be intelligently applied within an
iRule applied to a virtual server. However there are settings to permit SNAT functions in
other areas of the configuration. Within the settings of a pool configuration
Link to Online Topic Content
SNATs and NATs
When configuring a pool, you can specifically disable any secure network address
translations (SNATs) or network address translations (NATs) for any connections that
use that pool. By default, these settings are enabled. You can change this setting on an
existing pool by displaying the Properties screen for that pool.
One case in which you might want to configure a pool to disable SNAT or NAT
connections is when you want the pool to disable SNAT or NAT connections for a
specific service. In this case, you could create a separate pool to handle all connections
for that service, and then disable the SNAT or NAT for that pool.
Allow SNAT setting
You can configure a pool so that SNATs are automatically enabled or disabled for any
connections using that pool.
This setting’s default value is Yes.
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3.03 - Explain how persistence settings can override connection limits
Link to Online Topic Content
It is understood that persistence will keep a users session on the same pool member
according to the configuration of the type of persistence method that is being used.
And if connection limits were set for that pool member; it would also be understood
that if that pool member reached its limit, no further connections would be allowed.
This behavior would break the users session. To solve this type of problem the Override
Connection Limit setting can be enabled in the persistence profile.
Override Connection Limit setting
This setting can be enabled in the persistence profile.
It specifies, when checked (enabled), that the system allows you to specify that pool
member connection limits are overridden for persisted clients. Per-virtual connection
limits remain hard limits and are not overridden.
This setting is not enabled by default.
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3.03 - Describe the relationship between monitors and state
Link to Online Topic Content
Both Monitors and State settings will determine if a node or pool member is accessible.
A monitor is an important BIG-IP feature that verifies connections to pool members or
nodes. A health monitor is designed to report the status of a pool, pool member, or
node on an ongoing basis, at a set interval. When a health monitor marks a pool, pool
member, or node down, the BIG-IP system stops sending traffic to the device.
A failing or misconfigured health monitor may cause traffic management issues similar,
but not limited, to the following:



Connections to the virtual server are interrupted or fail.
Web pages or applications fail to load or execute.
Certain pool members or nodes receive more connections than others.
The previously mentioned symptoms may indicate that a health monitor is marking a
pool, pool member, or node down indefinitely, or that a monitor is repeatedly marking a
pool member or node down and then back up (often referred to as a bouncing pool
member or node). For example, if a misconfigured health monitor constantly marks
pool members down and then back up, connections to the virtual server may be
interrupted or fail altogether. You will then need to determine whether the monitor is
misconfigured, the device or application is failing, or some other factor is occurring that
is causing the monitor to fail (such as network-related issue). The troubleshooting steps
you take will depend on the monitor type and the observed symptoms.
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3.03 - Describe the functionality of Action On Service Down
Link to Online Topic Content
Action On Service Down
The Action On Service Down feature allows the BIG-IP system to choose another pool
member and rebind the client connection to a new server connection if the target pool
member becomes unavailable.
When a pool member fails to respond, as configured, to a health monitor, the system
marks that pool member down, and continues to monitor it to determine when the
member becomes available again. While a pool member is marked down, the system
does not send any new connections to that pool member.
The Action On Service Down feature specifies how the system should respond to
already-established connections when the target pool member becomes unavailable.
The available settings for this feature as follows:
None:
The BIG-IP system takes no action on existing connections, and removes the connection
table entry based on the associated profile's idle timeout value. The BIG-IP system
sends a TCP Reset (RST) or ICMP Unreachable once idle timeout is reached. This is the
default setting.
This is the best option for most common scenarios, as this allows for endpoints to
resume gracefully on their own. This may be a good choice for clients that transfer large
amounts of data, as the pool member may recover itself before the connection is reset,
allowing the large transfer to continue.
Reject:
The BIG-IP system sends RST or ICMP messages to reset active connections and removes
them from the BIG-IP connection table.
This may be a good choice for clients that need to be notified of pool member state
changes sooner than the configured idle timeout period for that virtual server. Once the
target pool member is deemed unavailable, the BIG-IP system immediately alerts the
client by resetting the connection, causing the client to attempt a new connection.
Drop:
The BIG-IP system silently removes the connection table entry.
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You should carefully consider this option, as the client receives no feedback from the
BIG-IP system regarding the connection state. However, this option works well for
short-lived, connectionless protocols, such as UDP. For example, DNS queries.
Reselect:
The BIG-IP system manages established client connections by moving them to an
alternate pool member without a connection teardown or setup.
This option is only appropriate for:

Virtual servers with address and port translation disabled
Note: This is default for FastL4 type virtual servers, such as network or wildcard
forwarding.

Transparent pool members, such as firewalls, routers, proxy servers, and cache
servers
Note: Transparent devices can forward packets to destinations without regard for the
state of the connection.

UDP virtual servers
Note: When choosing the Reselect option for Action on Service Down, the BIG-IP system
does not reform existing TCP connections, but continues to forward existing connections. If
the back-end pool members are not transparent devices, and the virtual server has address
translation enabled, all existing TCP connections sent to a pool member will likely reset due
to the pool member having no record of these ongoing connections in its connection table.
This is analogous to choosing the Reset action, except the pool members will be resetting
the connections instead of the BIG-IP system. F5 highly recommends choosing a different
Action on Service Down option, if you do not meet the above criteria for the Reselect
option.
Note: Services, such as HTTP require that the system establish a transport layer connection
before transmitting HTTP messages. This is commonly referred to as a 3-way handshake,
and is used by the client or server to establish communication options and to track requests
or responses. When a server receives a request from a client without having established the
transport layer connection, normal behavior is for the server to reject the connection by
sending a TCP response with the RST flag set. For more information, refer to Internet
Engineering Task Force (RFC 793), section Reset Generation. This link takes you to a
resource outside of AskF5. The third party could remove the document without our
knowledge.
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3.03 - Describe the functionality of Priority Group Activation
Link to Online Topic Content
Priority Group Activation
With the Priority Group Activation feature, you can specify the minimum number of
members that must remain available in each priority group in order for traffic to remain
confined to that group. This feature is used in tandem with the Priority Group feature
for individual pool members.
If the number of available members assigned to the highest priority group drops below
the minimum number that you specify, Local Traffic Manager distributes traffic to the
next highest priority group, and so on. As members become available again in the
higher group the Local Traffic Manager will disable the lower priority group as
necessary.
The configuration shown in Figure 3.03a has three priority groups, 3, 2, and 1, with the
Priority Group Activation value (shown as min active members) set to 2.
Figure 3.03a Sample pool configuration for priority load balancing
pool my_pool {
lb_mode fastest
min active members 2
member 10.12.10.7:80 priority 3
member 10.12.10.8:80 priority 3
member 10.12.10.9:80 priority 3
member 10.12.10.4:80 priority 2
member 10.12.10.5:80 priority 2
member 10.12.10.6:80 priority 2
member 10.12.10.1:80 priority 1
member 10.12.10.2:80 priority 1
member 10.12.10.3:80 priority 1
}
Connections are first distributed to all pool members with priority 3 (the highest priority
group). If fewer than two priority 3 members are available, traffic is directed to the
priority 2 members as well. If both the priority 3 group and the priority 2 group have
fewer than two members available, traffic is directed to the priority 1 group. Local
Traffic Manager continuously monitors the priority groups, and each time a higher
priority group once again has the minimum number of available members, Local Traffic
Manager limits traffic to that group.
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3.03 - Describe the persistence across pools and services (e.g., Match
Across Services, Match Across vs Match Across Pools)
Link to Online Topic Content
Match Across To Solve Deeper Persistence Issues
The Match Across options specify that, regardless of the type of persistence you are
implementing, you can specify the criteria that the BIG-IP system uses to send all
requests from a client to the same pool member. The criteria are based on the virtual
servers that are hosting the client connection.
Match Across Services
The Match Across Services option is used in the following two configurations:


Configurations that have multiple virtual servers with the same IP address but have
different services specified.
Configurations that have pool members sharing the same address but have different
services specified.
Important: The Match Across Services option uses only the node IP address to find a
persistence match in pools other than the one for which the persistence record was
written. This deviation from the normal persistence matching behavior is required to
accommodate the intended use cases for the feature to match even when the service
port does not. Because of this lack of granularity, a pool containing multiple members
with the same node address may result in inconsistent load balancing behavior. For this
reason, F5 recommends that pools associated with virtual servers that are configured to
use the Match Across Services option should not contain multiple members using the
same node address.
A typical use of the Match Across Services feature is for combined HTTP/HTTPS support
for the same site. Commerce sites are typically configured to allow customers to view
and select merchandise using HTTP, but then the site switches to HTTPS when the
customer begins the checkout process. The Match Across Services option is useful in
this configuration as it allows the session information to be shared between the virtual
servers and ensures that the client is directed to the same pool member.
The example, the configuration below shows that clients are load balanced to pool
member 172.16.1.2:http, and an entry is created in the persistence table when they first
connect to virtual server 192.168.0.10:http.
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If the same clients connect to virtual server 192.168.0.10:https, the BIG-IP system uses
the persistence session information that was established with the initial connection, and
directs the request to pool member 172.16.1.2:https.
If the same clients connect to virtual server 192.168.0.20:http, the request is load
balanced according to the method specified by the pool, and a new persistence session
is entered in the persistence table for tracking.
Note: This behavior occurs because the third virtual server does not share the same address
as the other two that are configured.
If the client connects to a different virtual server that does not utilize persistence, that
connection will be load balanced according to the load balancing option specified by the
pool for that virtual server.
The following configuration shows how a request is directed with the Match Across
Services option enabled:
HTTP Virtual Server: 192.168.0.10:http
Type of Persistence Used: Source Address Affinity and
Match Across Services enabled
HTTP Pool Name: http_pool
HTTP Pool Members: 172.16.1.1:http
172.16.1.2:http
172.16.1.3:http
HTTPS Virtual Server: 192.168.0.10:https
Type of Persistence Used: Source Address Affinity and
Match Across Services enabled
HTTPS Pool Name: https_pool
HTTPS Pool Members: 172.16.1.1:https
172.16.1.2:https
172.16.1.3:https
HTTP Virtual Server: 192.168.0.20:http
Type of Persistence Used: Source Address Affinity and
Match Across Services enabled
HTTP Pool Name: http2_pool
HTTP Pool Members: 172.16.1.1:8443
172.16.1.2:8443
172.16.1.3:8443
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Match Across Virtual Servers
Match Across Virtual Servers is similar to Match Across Services, but it does not require
the virtual servers to share the same IP address. This configuration allows clients to
access different virtual servers, regardless of their IP address, and still access the same
pool member.
The example configuration below shows that clients are load balanced to pool member
172.16.1.2:http, and an entry is created in the persistence table when they first connect
to virtual server 192.168.0.10:http.
If the same clients connect to virtual server 192.168.0.10:https, the BIG-IP system uses
the persistence session information that was established with the initial connection to
virtual server 192.168.0.10:http, and directs the request to pool member
172.16.1.2:https.
If the same clients connect to virtual server 192.168.0.20:http, the BIG-IP uses the
persistence session information that was established with the initial connection to
virtual server 192.168.0.10:http and directs the request to pool member
172.16.1.2:8443.
Note: This behavior occurs because the pool members used by virtual server
192.168.0.20:http have the same node IP as those specified in the http_pool used by
virtual server 192.168.0.10:http.
If the client connects to a different virtual server that does not use persistence, that
connection will be load balanced according to the load balancing option specified by the
pool for that virtual server.
The following configuration shows how a request is directed when the Match Across
Virtual Servers option is enabled:
HTTP Virtual Server: 192.168.0.10:http
Type of Persistence Used: Source Address Affinity and
Match Across Virtuals enabled
HTTP Pool Name: http_pool
HTTP Pool Members: 172.16.1.1:http
172.16.1.2:http
172.16.1.3:http
HTTPS Virtual Server: 192.168.0.10:https
Type of Persistence Used: Source Address Affinity and
Match Across Virtuals enabled
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HTTPS Pool Name: https_pool
HTTPS Pool Members: 172.16.1.1:https
172.16.1.2:https
172.16.1.3:https
HTTP Virtual Server: 192.168.0.20:http
Type of Persistence Used: Source Address Affinity and
Match Across Virtuals enabled
HTTP Pool Name: http2_pool
HTTP Pool Members: 172.16.1.1:8443
172.16.1.2:8443
172.16.1.3:8443
Match Across Pools
The Match Across Pools option allows the BIG-IP system to use any pool that contains a
persistence record for that specific client. You must proceed cautiously when using this
option, as it can direct a client's request to a pool that is not specified by the virtual
server.
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3.03 - Describe how connection limits are affected by node, pool and
virtual server settings
Link to Online Topic Content
Pool member connection limits can be affected by settings in multiple areas of the
configuration. Connection limits on a pool member can be affected by having
connection limits set on the associated node. If there is connection limits set on the
node and that setting is lower than the connection limit of the associated pool member,
then the pool member can never reach its full limit. Likewise if the node is defined in
multiple pools all connections to the node from the other pools count toward the node
level connection limit which can restrict the number of connections to the pool member
with connection limits set.
Virtual servers can have connection limits and persistence configured where each could
affect connection limit settings at the pool level. The corresponding persistence profile
can be set to allow “Override Connection Limits” described in a previous section.
Connection limits on the virtual server can affect connection levels to the pool member
if the virtual server setting is lower than the setting at the pool member level.
Vice versa, the connection limits at the pool level can affect the connection limits set in
the virtual server configuration. If there are connection limits set on the pool members
of a virtual servers associated pool, and the total of the pool members connection limits
are less than the virtual server’s connection limits then the virtual server can never
reach its full limit.
Connection limits configured on pool members or nodes for a CMP system are enforced
per TMM instance
The BIG-IP system divides the configured connection limit by the number of Traffic
Management Microkernels (TMMs) that are running on the system, and forces the
calculated limit to round down to the nearest whole number, per TMM. For example,
when a pool member or node is configured with a connection limit of 10 on a CMP
system with four running TMMs, the BIG-IP system divides the configured limit of 10 by
four TMMs, and enforces the calculated connection limit of two on each running TMM.
This is expected behavior.
Note: If you use a pool member or node that is configured with very low connection limits,
the system may appear to enforce lower than expected connection limits. In addition, F5
does not recommend that you configure a connection limit to a number lower than the
number of TMM instances supported by the platform; doing so may result in unpredictable
connection counts.
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3.03 - Describe how priority groups are affected by connection limits
Link to Online Topic Content
When a connection limit is set on a pool member, the pool member can receive that
specific count of concurrent connections as a maximum. If the pool member has
reached the connection limit and is temporarily unavailable, it will not count as an
unavailable pool member that could trigger the priority group to activate the next group
of pool members. Thus the pool could run out of available connections and still never
activate an additional priority group in the pool.
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Conclusion
This document is intended as a study guide for the F5 301a – LTM Specialist: Architect,
Set-Up & Deploy exam. This study guide is not an all-inclusive document that will
guarantee a passing grade on the exam. It is intended to be a living doc and any
feedback or material that you feel should be included, to help exam takers better
prepare, can be sent to channeleng@f5.com.
Thank you for using this study guide to prepare the 301a – LTM Specialist exam and
good luck with your certification goals.
Thanks
Eric Mitchell
Channel FSE, East US and Federal
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