null  null
SBA
BORDERLESS
NETWORKS
DEPLOYMENT
GUIDE
LAN Deployment Guide
S M A R T
B USI NE S S
A R C HI TEC TURE
August 2012 Series
Preface
Who Should Read This Guide
How to Read Commands
This Cisco® Smart Business Architecture (SBA) guide is for people who fill a
variety of roles:
Many Cisco SBA guides provide specific details about how to configure
Cisco network devices that run Cisco IOS, Cisco NX-OS, or other operating
systems that you configure at a command-line interface (CLI). This section
describes the conventions used to specify commands that you must enter.
• Systems engineers who need standard procedures for implementing
solutions
• Project managers who create statements of work for Cisco SBA
implementations
Commands to enter at a CLI appear as follows:
• Sales partners who sell new technology or who create implementation
documentation
Commands that specify a value for a variable appear as follows:
• Trainers who need material for classroom instruction or on-the-job
training
Commands with variables that you must define appear as follows:
configure terminal
ntp server 10.10.48.17
class-map [highest class name]
In general, you can also use Cisco SBA guides to improve consistency
among engineers and deployments, as well as to improve scoping and
costing of deployment jobs.
Commands shown in an interactive example, such as a script or when the
command prompt is included, appear as follows:
Release Series
Long commands that line wrap are underlined. Enter them as one command:
Cisco strives to update and enhance SBA guides on a regular basis. As
we develop a series of SBA guides, we test them together, as a complete
system. To ensure the mutual compatibility of designs in Cisco SBA guides,
you should use guides that belong to the same series.
The Release Notes for a series provides a summary of additions and
changes made in the series.
All Cisco SBA guides include the series name on the cover and at the
bottom left of each page. We name the series for the month and year that we
release them, as follows:
month year Series
For example, the series of guides that we released in August 2012 are
the “August 2012 Series”.
Router# enable
wrr-queue random-detect max-threshold 1 100 100 100 100 100
100 100 100
Noteworthy parts of system output or device configuration files appear
highlighted, as follows:
interface Vlan64
ip address 10.5.204.5 255.255.255.0
Comments and Questions
If you would like to comment on a guide or ask questions, please use the
SBA feedback form.
If you would like to be notified when new comments are posted, an RSS feed
is available from the SBA customer and partner pages.
You can find the most recent series of SBA guides at the following sites:
Customer access: http://www.cisco.com/go/sba
Partner access: http://www.cisco.com/go/sbachannel
August 2012 Series
Preface
Table of Contents
What’s In This SBA Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Access Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Cisco SBA Borderless Networks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Business Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Route to Success. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Technology Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
About This Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Access Layer Platforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Related Reading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Design Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Business Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Offer Reliable Access to Organization
Resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Minimize Time Required to Absorb
Technology Investments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Consistent User Experience. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Reduce Operational Costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Deployment Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Configuring the Access Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Distribution Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Business Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Technology Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Distribution Layer Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Deployment Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Configuring the Distribution Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Core Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Business Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Architecture Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Technology Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Hierarchical Design Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Core Layer Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Access Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Deployment Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Distribution Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Configuring the Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Core Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Quality of Service (QoS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Appendix A: Product List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Appendix B: Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
August 2012 Series
Table of Contents
What’s In This SBA Guide
Cisco SBA Borderless Networks
About This Guide
Cisco SBA helps you design and quickly deploy a full-service business
network. A Cisco SBA deployment is prescriptive, out-of-the-box, scalable,
and flexible.
This deployment guide contains one or more deployment chapters, which
each include the following sections:
Cisco SBA incorporates LAN, WAN, wireless, security, data center, application
optimization, and unified communication technologies—tested together as a
complete system. This component-level approach simplifies system integration
of multiple technologies, allowing you to select solutions that solve your
organization’s problems—without worrying about the technical complexity.
Cisco SBA Borderless Networks is a comprehensive network design
targeted at organizations with up to 10,000 connected users. The SBA
Borderless Network architecture incorporates wired and wireless local
area network (LAN) access, wide-area network (WAN) connectivity, WAN
application optimization, and Internet edge security infrastructure.
• Business Overview—Describes the business use case for the design.
Business decision makers may find this section especially useful.
• Technology Overview—Describes the technical design for the
business use case, including an introduction to the Cisco products that
make up the design. Technical decision makers can use this section to
understand how the design works.
• Deployment Details—Provides step-by-step instructions for deploying
and configuring the design. Systems engineers can use this section to
get the design up and running quickly and reliably.
You can find the most recent series of Cisco SBA guides at the following
sites:
Route to Success
Customer access: http://www.cisco.com/go/sba
To ensure your success when implementing the designs in this guide, you
should first read any guides that this guide depends upon—shown to the
left of this guide on the route below. As you read this guide, specific
prerequisites are cited where they are applicable.
Partner access: http://www.cisco.com/go/sbachannel
Prerequisite Guides
You Are Here
Dependent Guides
BORDERLESS
NETWORKS
LAN Design Overview
August 2012 Series
LAN Deployment Guide
Additional Deployment Guides
What’s In This SBA Guide
1
Introduction
The Cisco SBA—Borderless Networks LAN Deployment Guide describes
how to deploy a wired network access with ubiquitous capabilities that scale
from small environments with one to a few LAN switches to a large campussize LAN. Resiliency, security, and scalability are included to provide a
robust communications environment. Quality of service (QoS) is integrated
to ensure that the base architecture can support a multitude of applications
including low latency, drop-sensitive multimedia applications that coexist
with data applications on a single network.
Design Goals
The Cisco SBA LAN architecture is designed to meet the needs of organizations with LAN connectivity requirements that range from a small remotesite LAN to up to 5,000 connected users at a single location.
Organizations with up to 10,000 users are often spread out among different geographical locations, making flexibility and scalability a critical
requirement of the network. This design uses several methods to create and
maintain a scalable network:
Cisco SBA Borderless Networks is a solid network foundation designed to
provide networks with up to 10,000 connected users the flexibility to support new users or network services without re-engineering the network. This
is a prescriptive, out-of-the-box deployment guide that is based on bestpractice design principles and that delivers flexibility and scalability.
Related Reading
The Cisco SBA—Borderless Networks LAN Design Overview orients you
to the overall Cisco SBA design and explains the requirements that were
considered when selecting specific products.
The Cisco SBA—Borderless Networks Wireless LAN Deployment Guide
focuses on deploying Cisco Unified Wireless Network in multiple network
locations and includes multiple scale models to meet the various LAN
deployment sizes. The deployment guide uses a controller-based wireless
design. By centralizing configuration and control on a Cisco wireless LAN
controller (WLC), the wireless LAN can operate as an intelligent information
network and support advanced services. This centralized deployment simplifies operational management by collapsing large numbers of managed
endpoints and autonomous access points into a single managed system.
August 2012 Series
This architecture is based on requirements gathered from customers,
partners, and Cisco field personnel for organizations with up to 10,000
connected users. When designing the architecture, Cisco considered the
gathered requirements and the following design goals.
Ease of Deployment, Flexibility, and Scalability
• By keeping a small number of standard designs for common portions of
the network, support staff is able to design services for, implement, and
support the network more effectively.
• This modular design approach enhances scalability. Beginning with a
set of standard, global building blocks, you can assemble a scalable
network to meet requirements.
• Many of the plug-in modules look identical for several service areas; this
common look provides consistency and scalability so that you can use
the same support methods to maintain multiple areas of the network.
These modules follow standard core-distribution-access network design
models and use layer separation to ensure that interfaces between the
plug-ins are well defined.
Introduction
2
Figure 1 - Scalable architecture to meet multiple requirements
Two-Tier Collapsed LAN Core
Two-Tier Remote-Site LAN
Server
Room
WAN
Wireless LAN
Controller
WAN
Routers
Wireless LAN
Controller
Distribution
Switch Stack
WAN
Modular
Distribution Switch
Firewall
Internet
Client
Access
Switches
Client
Access
Switches
Three-Tier LAN Design
Data
Center
LAN Core
Layer
Remote Building
Aggregation LAN
Distribution Module
High Density LAN
Distribution Module
Client
Access
Switches
Network Services
Distribution Module
Wireless LAN
Controller
Firewall
Client
Access
Switches
WAN
2082
Internet
August 2012 Series
Introduction
3
The modular design of the Cisco SBA LAN architecture provides multiple
scale points to meet your organization’s specific requirements, including:
• A highly resilient and scalable distribution layer with two modular
chassis-based platforms using the Cisco Catalyst 6500 Virtual
Switching System (VSS), that acts as a single logical distribution layer
platform. This design allows for high density aggregation of Gigabit
Ethernet and 10 Gigabit Ethernet connected wiring closets and other
platforms. Cisco Catalyst 6500 VSS provides the most advanced feature
set and the highest resiliency of the available platforms.
• A resilient modular chassis distribution layer design for locations where
there is a mix of Gigabit Ethernet or 10 Gigabit Ethernet connected
wiring closets that need to be aggregated. Cisco Catalyst 4507 with dual
supervisors and dual power supplies provides resiliency with Cisco IOS
In-Service Software Upgrades (ISSU) and sub-second failover.
• A stackable Cisco Catalyst 3750-X distribution layer switch to accommodate locations where there is a small number of gigabit connected wiring
closets and other platforms that need to be aggregated. Cisco Catalyst
3750-X provides a resilient platform with StackWise and StackPower.
• To accommodate the most demanding LAN requirements, a three
tier network design incorporates one or many of the distribution layer
designs connected to a highly-reliable Core layer. As the LAN design
scales, the modules that make up the design remain consistent to
provide a scalable environment.
Ease of Management
While this guide focuses on the deployment of the network foundation, the
design takes next phase management and operation into consideration. The
configurations in the deployment guides are designed to allow the devices
to be managed via normal device management connections, such as SSH
and HTTPS, as well as via the Network Management System (NMS). The
configuration of the NMS is not covered in this guide.
Advanced Technology–Ready
Flexibility, scalability, resiliency, and security all are characteristics of an
advanced technology-ready network. The modular design of the architecture means that technologies can be added when the organization is ready
to deploy them. However, the deployment of advanced technologies, such
as multimedia-based collaboration tools, is eased because the architecture
includes products and configurations that are ready to support collaboration
from day one. For example:
• Access switches provide Power over Ethernet (PoE) up to 60 watts per
port for line-powered phone, camera, and virtual desktop deployments
without the need for a local power outlet.
• The entire network is configured with QoS to support high-quality voice.
• Multicast is configured in the network to support efficient voice and
broadcast-video delivery.
Resiliency and Security
One of the keys to maintaining a highly available network is building the
appropriate resilience into the network links and networking platforms to
guard against single points of failure in the network. The SBA LAN architecture is carefully designed to avoid the complexity inherent in redundant
systems.
With the addition of a significant amount of delay-sensitive and dropsensitive traffic such as voice and video conferencing, Cisco also places a
strong emphasis on recovery times. Choosing designs that reduce the time
between failure detection and recovery is important for ensuring that the
network stays available even in the face of a link or component failure.
Network security is also a strong component of the architecture. In a large
network, there are many entry points and the SBA LAN design ensures that
they are as secure as possible without making the network too difficult to
use. Securing the network not only helps keep the network safe from attacks
but is also a key component to network-wide resiliency.
August 2012 Series
Introduction
4
Business Overview
The LAN Deployment Guide is designed to address four primary requirements shared by organizations, including the need to:
• Offer reliable access to organization resources
• Minimize time required to absorb technology investments
• Provide a productive and consistent user experience
• Reduce operation costs
Offer Reliable Access to Organization
Resources
Data networks are critical to an organization’s viability and productivity.
Online workforce-enablement tools are only beneficial if the data network
provides reliable access to information resources. Collaboration tools and
content distribution rely on high-speed, low-latency network infrastructure
to provide an effective user experience. However, as networks become more
complex, the level of risk increases for network availability loss or poor performance due to inadequate design, configuration errors, maintenance and
upgrade outages, or hardware and software faults. The design and methods
used in this deployment guide were created to minimize these risks.
Minimize Time Required to Absorb
Technology Investments
New technology can impose significant costs, from the perspective of the
investment in the equipment, as well as the time and workforce investment
required to deploy the new technology and establish operational readiness. When new technology is introduced it takes time to understand how
the technology operates, and to ascertain how to effectively integrate the
new technology into the existing infrastructure. Over time the methods and
procedures used to deploy a new technology are refined and become more
efficient and accurate.
August 2012 Series
This deployment guide helps your organization reduce the cost of technology implementation by providing methods and procedures that have
been developed and tested by Cisco. By applying the guidance within this
document, you reduce the time required to assimilate the technology into
the organization’s network, and you can deploy the technology quickly and
accurately, so your organization can achieve a head start in realizing the
return on its investment.
Consistent User Experience
The number of users and locations in an organization can vary dramatically as an organization grows and adapts to changes in business activity.
Providing a consistent user experience when users connect to the network
increases their productivity. Whether users are sitting in an office at headquarters or working from a remote site, they require transparent access to
the applications and files to perform their jobs. When the IT organization can
offer a standardized and template-based LAN design that scales from small
to large locations they can reduce their time to deploy new locations while
maintaining a consistent access experience for their users.
Reduce Operational Costs
Organizations constantly pursue opportunities to reduce network operational costs, while maintaining the network’s effectiveness for end users.
Operational expenses include not only the cost of the physical operation (for
example, power, cooling, etc.), but also the labor cost required to staff an IT
department that monitors and maintains the network. Additionally, network
outages and performance issues impose costs that are more difficult to
quantify, in the form of loss of productivity and interruption of business
continuity.
The network described by this deployment guide offers network resilience
in its ability to tolerate failure or outage of portions of the network, along with
a sufficiently robust-yet-simple design that staff should be able to operate,
troubleshoot, and return to service in the event of a network outage.
Business Overview
5
Architecture Overview
The LAN is the networking infrastructure that provides access to network
communication services and resources for end users and devices spread
over a single floor or building. A campus network occurs when a group of
building-based LANs that are spread over a small geographic area are
interconnected.
The LAN Deployment Guide provides a design that enables communications between devices in a building or group of buildings, as well as interconnection to the WAN and Internet Edge modules at the network core.
Specifically, this document shows you how to deploy the network foundation
and services to enable
A hierarchical design includes the following three layers:
• Access layer—Provides workgroup/user access to the network.
• Distribution layer—Aggregates access layers and provides connectivity
to services.
• Core layer—Provides connection between distribution layers for large
LAN environments.
Figure 2 - LAN hierarchical design
Core
• Tiered LAN connectivity for up to 5,000 connected users
• Wired network access for employees
• IP Multicast for efficient data distribution
• Wired infrastructure ready for multimedia services
Distribution
This architecture uses a hierarchical design model to break the design up
into modular groups or layers. Breaking the design up into layers allows
each layer to focus on specific functions, which simplifies the design and
provides simplified deployment and management.
Modularity in network design allows you to create design elements that can
be replicated throughout the network. Replication provides an easy way to
scale the network as well as a consistent deployment method.
In flat or meshed network architectures, changes tend to affect a large number of systems. Hierarchical design helps constrain operational changes to
a subset of the network, which makes it easy to manage as well as improve
resiliency. Modular structuring of the network into small, easy-to-understand
elements also facilitates resiliency via improved fault isolation.
August 2012 Series
Client
Access
1002
Hierarchical Design Model
The three layers—access, distribution, and core—each provide different
functionality and capability to the network. Depending on the characteristics
of the site where the network is being deployed, you might need one, two, or
all three of the layers. For example, a remote site supporting only 10 users
will only require an access layer. A site that occupies a single building might
only require the access and distribution layers, while a campus of multiple
buildings will most likely require all three layers.
Architecture Overview
6
Regardless of how many layers are implemented at a site, the modularity of
this design ensures that each layer will always provide the same services,
and in this architecture, will use the same deployment methods.
Figure 4 - Access layer connectivity
Handheld
Figure 3 - Scalability by using a modular design
Wireless
Access Point
Access
Switch
Core
LAN, WAN
and Internet
Personal
Telepresence
Distribution
SCALE
Client
Access
2084
Client
Access
User
Access Layer
The access layer is the point at which user-controlled and user-accessible
devices are connected to the network. The access layer provides both wired
and wireless connectivity and contains features and services that ensure
security and resiliency for the entire network.
Device Connectivity
The access layer provides high-speed user-controlled and user-accessible
device connectivity. Once expensive options, high-speed access technologies like Gigabit Ethernet and 802.11n wireless are now standard configurations on end-user devices. While an end-user device in most cases will
not use the full capacity of these connections for long periods of time, the
ability to burst up to these high speeds when performing routine tasks does
help make the network a transparent part of an end-users day-to-day job.
The longer someone has to wait to back up their machine, send an email,
or open a file off an internal web page the harder it is for the network to be
transparent.
August 2012 Series
2085
Core/
Distribution
IP Phone
It is common for many different types of devices to connect at the access
layer. Personal computers, IP phones, wireless access points, and IP video
surveillance cameras all might connect to the same access layer switch.
Since it can be beneficial for performance, management, and security
reasons to segment these different devices, the access layer provides the
capability to support many logical networks on one physical infrastructure.
Resiliency and Security Services
In general, the goal of the resiliency and security services in the infrastructure is to ensure that the network is available for use without impairment
for everyone that needs it. Because the access layer is the connection
point between the network and client devices, it plays a role in ensuring
the network is protected from human error and from malicious attacks. This
protection includes making sure the devices connecting to the network do
not attempt to provide services to any end users that they are not authorized
for, that they do not attempt to take over the role of any other device on the
network, and, when possible, that they verify the device is allowed on the
network.
Enabling these services in the access layer contributes not only to the
overall security of the network, but also to the resiliency and availability of
the network.
Architecture Overview
7
Advanced Technology Capabilities
Reduce Complexity and Increase Resiliency
Finally, the access layer provides a set of network services that support
advanced technologies. Voice and video are commonplace in today’s organizations and the network must provide services that enable these technologies. This includes providing specialized access for these devices, ensuring
the traffic from these devices is not impaired by others, and providing
efficient delivery of traffic that is needed by many devices in the network.
This design uses a simplified distribution layer design, which consists of a
single logical entity that can be implemented using a pair of physically separate switches operating as one device, a physical stack of switches operating as one device, or a single physical device with redundant components.
Distribution Layer
The distribution layer serves many important services for the LAN. The
primary function is to serve as an aggregation point for multiple access layer
switches in a given location or campus. In a network where connectivity
needs to traverse the LAN end-to-end, whether between different access
layer devices or from an access layer device to the WAN, the distribution
layer facilitates this connectivity.
Scalability
In any network where multiple access layer devices exist at a location to
serve end-user connectivity, it becomes impractical to interconnect each
access switch as the access layer grows beyond two or three switches.
The distribution layer provides a logical point to summarize addressing and
to create a boundary for protocols and features necessary for the access
layer operation. Another benefit of the distribution layer boundary is that it
creates fault domains that serve to contain failures or network changes to
those parts of the network directly affected.
The benefit to the organization is the reduced complexity of configuring and
operating the distribution layer as fewer protocols are required and little or
no tuning is needed to provide near-second or sub-second convergence
around failures or disruptions.
The design resiliency is provided by physically redundant components like
power supplies, supervisors, and modules, as well as stateful switchover
to redundant logical control planes. Reduced complexity and consistent
design lower the operational cost of configuring and maintaining the
network.
Flexible Design
The distribution layer provides connectivity to network-based services, to
the WAN, and to the Internet Edge. Network-based services can include and
are not limited to Wide Area Application Services (WAAS), and wireless LAN
controllers. Depending on the size of the LAN, these services and the interconnection to the WAN and Internet Edge may reside on a distribution layer
switch that also aggregates the LAN access layer connectivity. This is also
referred to as a “collapsed Core” design because the distribution serves as
the Layer 3 aggregation layer for all devices.
The end result to the organization is that the distribution layer can lower the
cost of operating the network by making it more efficient, by requiring less
memory, and by processing resources for devices elsewhere in the network.
The distribution layer also increases network availability by containing
failures to smaller domains.
August 2012 Series
Architecture Overview
8
Larger LAN designs require a dedicated distribution layer for network-based
services connectivity versus sharing one with access layer devices. As
the density of WAN routers, WAAS controllers, Internet Edge devices, and
wireless LAN controllers grows, the ability to connect to a single distribution
layer switch becomes hard to manage. There are a number of factors that
drive LAN design with multiple distribution layer modules:
Figure 5 - Two tier design: Distribution layer functioning as a collapsed Core
Servers
Firewall
• The number of ports and port speed that the distribution layer platform
can provide affects network performance and throughput.
Switch
Stack
• Network resilience is a factor when all LAN and network-based services
rely on a single platform, regardless of that platform’s design, it can
present a siingle point of failure or an unacceptably large failure domain.
Cisco ACE
Server
Room
• Change control and frequency affects resilience. When all LAN, WAN,
and other network services are consolidated on a single distribution
layer, operational or configuration errors can affect all network operation.
Wireless
LAN Controller
• Geographic dispersion of the LAN access switches across many buildings in a larger campus facility would require more fiber optic interconnects back to a single collapsed Core.
WAN
Routers
WAN
Distribution
Switch
Collapsed
LAN Core
Figure 6 - Network-services distribution layer
Firewall
LAN
Core
Wireless
LAN Controller
Internet
LAN
Distribution
Layer
Network Services
Distribution Layer
Firewall
Client
Access
Switches
Client
Access
Switches
Internet
August 2012 Series
2086
LAN
Access
2087
WAN
Architecture Overview
9
Like the access layer, the distribution layer also provides QoS for application
flows to guarantee critical applications and multimedia applications perform
as designed.
Figure 8 - LAN topology without a core layer
Core Layer
Another reason to use multiple distribution layer switches is when the
number of access layer switches connecting to a single distribution layer
exceeds the performance goals of the network designer. In a modular and
scalable design, you can collocate distribution layers for data center, WAN
connectivity, or Internet Edge services.
In environments where multiple distribution layer switches exist in close
proximity and where fiber optics provide the ability for high-speed interconnect, a core layer reduces the network complexity, as shown in the following
two figures.
Figure 7 - LAN topology with a core layer
2089
In a large LAN environment there often arises a need to have multiple
distribution layer switches. One reason for this is that when access layer
switches are located in multiple geographically dispersed buildings, you
can save costly fiber-optic runs between buildings by locating a distribution
layer switch in each of those buildings. As networks grow beyond three
distribution layers in a single location, organizations should use a core layer
to optimize the design.
The core layer of the LAN is a critical part of the scalable network, and yet it
is one of the simplest by design. The distribution layer provides the fault and
control domains, and the core represents the 24x7x365 nonstop connectivity between them, which organizations must have in the modern business
environment where connectivity to resources to conduct business is critical.
In this design, the core layer is based on two physically and logically
separate switches. Connectivity to and from the core is Layer 3 only, which
drives increased resiliency and stability. Since the core does not need to
provide the same services or boundaries that the distribution layer does, the
two-box design is not an issue of any significant increase in configuration or
complexity.
2088
Core
August 2012 Series
Architecture Overview
10
Quality of Service (QoS)
Because real-time traffic is very sensitive to delay and drop, organizations
need to provide special handling for it on the network. The network must
ensure that this type of traffic is handled with priority so that the stream of
audio or video is not interrupted.
QoS allows the organization to define different traffic types and to create
more deterministic handling for real-time traffic. QoS is especially useful in
congestion handling, where a full communications channel might prevent
voice or video streams from being intelligible at the receiving side. It is
important to note, however, that QoS does not create bandwidth; rather, it
takes bandwidth from one class (that is, generally the default traffic class) to
give some priority to another class.
Within this design the approach to using QoS capabilities is to keep the QoS
profiles as simple as necessary to meet the goals for supporting applications that need special delivery. The primary goals of implementing QoS
within the network are:
• Support and ensure first out-the-door service for supported, real-time
applications.
• Provide business continuance for business-critical applications.
• Provide fairness between all other applications when congestion occurs.
• Build a trusted edge around the network to guarantee that users cannot
inject their own arbitrary priority values and to allow the organization to
trust marked traffic throughout the network.
To accomplish these goals, the design uses a three-step approach to
implementing QoS across the network as follows:
• Establish a limited number of traffic classes (that is, one to eight classes)
within the network that need special handling (for example, real-time
voice, real-time video, high-priority data, interactive traffic, batch traffic,
and default classes).
• Classify applications into the traffic classes.
• Apply special handling to the traffic classes to achieve intended network
behavior.
In this design, QoS configurations are as simple as possible, and are applied
only to those applications that require special handling.
This approach establishes a solid, scalable, and modular framework to
implement QoS across the entire network.
August 2012 Series
Architecture Overview
11
Access Layer
Business Overview
To conduct business in today’s competitive global economy, organizations
rely on the flow of information. They must provide a dispersed workforce
with access to applications that support informed business decisions and
the ability to check email correspondence from internal and external associates. Therefore, the ability to move information around the organization is
critical. By ensuring that users have the ability to access this information
or push communications regardless of their location using an increasingly
diverse set of communications devices, the organization is able to help the
workforce become more productive. The speed, reliability, and availability of
the transport are critical to success.
Transforming the communication of ideas and information from flat written
text to a multimedia experience by adding audio and video improves the
receivers’ understanding and retention of that information. As organizations evolve their ability to deliver these richer modes of communication,
they face the challenge of controlling the cost of deployment with a single
infrastructure to accommodate what used to require multiple parallel singlepurpose networks.
Technology Overview
The access layer is the point at which user-controlled and user-accessible
devices are connected to the network and it is the one architecture component that is found in every LAN.
Infrastructure Security Features
Because the access layer is the connection point between network-based
services and client devices it plays an important role in protecting other
users, the application resources, and the network itself from human error
and malicious attacks. Network resiliency and security in the access layer is
achieved through the use of Cisco Catalyst Infrastructure Security Features
(CISF) including DHCP snooping, IP Source Guard, port security, and
Dynamic ARP Inspection.
August 2012 Series
MAC flooding attacks are used to force a LAN switch to flood all their
traffic out to all the switch interfaces. Port security limits the number of
MAC addresses that can be active on a single port to protect against such
attacks.
Port security lets you to configure Layer 2 interfaces to allow inbound traffic
from only a restricted set of MAC addresses. The MAC addresses in the
restricted set are called secure MAC addresses. In addition, the device does
not allow traffic from these MAC addresses on another interface within the
same VLAN.
The number of MAC addresses that the device secures on each interface is
configurable. For ease of management, the device can learn the addresses
dynamically. Using the dynamic learning method, the device secures MAC
addresses while ingress traffic passes through the interface. If the address
is not yet secured and the device has not reached any applicable maximum,
it secures the address and allows the traffic. The device ages dynamic
addresses and drops them when the age limit is reached.
DHCP snooping is a DHCP security feature that blocks DHCP replies on an
untrusted interface. An untrusted interface is any interface on the switch not
specifically configured as a known DHCP server or path towards a known
DHCP server.
The DHCP snooping feature helps simplify management and troubleshooting by tracking MAC address, IP address, lease time, binding type, VLAN
number, and interface information that correspond to the local untrusted
interfaces on the switch. DHCP snooping stores that information in the
DHCP binding table.
Dynamic ARP inspection (DAI) mitigates ARP poisoning attacks. An ARP poisoning attack is a method by which an attacker sends false ARP information
to a local segment. This information is designed to poison the ARP cache
of devices on the LAN, allowing the attacker to execute man-in-the-middle
attacks.
Access Layer
12
Figure 9 - DHCP snooping and ARP inspection
AA
DD
10.4.10.10
10.4.10.20
1/24
EE
10.4.200.10
IP:10.4.10.10
MAC:AA
Untrusted
Distribution
Switch
OR
DHCP ACK or Bad Source IP
to Interface Binding
Untrusted
User
IP:10.4.10.20
MAC:DD
Remote
Router
Access
Switch
2091
1/1
1/2
Wireless
Access Point
Trusted Interface
to DHCP Server
(10.4.200.10)
IP Phone
2090
DHCP Snooping Binding Table
Port
MAC
IP
Figure 10 - Access layer overview
DAI uses the data generated by the DHCP snooping feature and intercepts
and validates the IP-to-MAC address relationship of all ARP packets on
untrusted interfaces. ARP packets that are received on trusted interfaces
are not validated and invalid packets on untrusted interfaces are discarded.
Features to Support Voice and Video Deployment
Voice and video are enabled in the access layer via network services such
as Power over Ethernet (PoE), QoS, multicast support, and Cisco Discovery
Protocol with the voice VLAN.
IP Source Guard is a means of preventing a packet from using an incorrect
source IP address to obscure its true source, also known as IP spoofing. IP
Source Guard uses information from DHCP snooping to dynamically configure a port access control list (PACL) on the interface that denies any traffic
from IP addresses that are not in the DHCP binding table.
PoE enables devices such as IP Phones, wireless access points, virtual
desktops, and security cameras to be powered by the access layer device.
This removes the expense of installing or modifying building power to support devices in difficult to reach locations and allows for the consolidation of
back-up power supplies and Universal Power Supplies (UPSs) to the access
closet.
Common Deployment Method to Simplify Installation and
Operation
To support the increasing requirements of devices powered by the network,
all of the access layer devices support the IEEE 802.3at standard, also
known as PoE+. The devices, and or line cards support all the previous
implementations of PoE up to 20 watts per port as well as the new IEEE
802.3at implementation of up to 30 watts per port. For the most demanding
PoE environments, like virtual desktops, the Catalyst 4500 in the access
layer has the ability to provide up to 60 watts of power per port with
Universal Power over Ethernet (UPoE) over the same cable plant as you use
for PoE+.
To provide consistent access capabilities and simplify network deployment
and operation, the design uses a common deployment method for all access
layer devices, whether they are located in the headquarters or at a remote
site. To reduce complexity, the access layer is designed so that you can use
a single interface configuration for a standalone computer, an IP phone, an
IP phone with an attached computer, or a wireless access point.
The LAN access layer provides high-speed connections to devices via
10/100/1000 Ethernet with both Gigabit and 10-Gigabit uplink connectivity
options. The 10 Gigabit uplinks also support Gigabit connectivity to provide
flexibility and help business continuity during a transition to 10 Gigabit
Ethernet. The LAN access layer is configured as a Layer 2 switch, with all
Layer 3 services being provided either by the directly-connected distribution layer or router.
August 2012 Series
Cisco Discovery Protocol supports voice and video device integration
into the access layer. Cisco IP Phones that are plugged into the access
layer communicate bidirectionally with the access layer switch via Cisco
Discovery Protocol. Cisco Discovery Protocol provides the IP Phone with
configuration information and provides the access layer switch with the IP
Phones power requirements and the ability to selectively prioritize traffic
from the IP Phone.
Access Layer
13
Access Layer Platforms
Wiring Closets Requiring up to 48 Ports
Cisco Catalyst 2960-S and 3560-X Series are both economical 10/100/1000
Ethernet fixed-port switches that provide flexibility and common features
required for wiring closets that can be supported by a single fixed port
switch. Cisco Catalyst 2960-S and 3560-X are available in both PoE+ and
non-powered versions.
In addition to the capabilities supported by Catalyst 2960-S (other than
stacking), Catalyst 3560-X supports modular uplinks, an upgradable Cisco
IOS feature set, and enhanced enterprise capabilities like Cisco TrustSec
and Medianet.
Wiring Closets Requiring Greater than 48 Ports
When a wiring closet requires greater interface density than can be provided by a single switch, an intelligent stack of fixed configuration switches
or a modular switch is recommended.
Intelligent stacks or modular Ethernet switches provide the following major
benefits:
• Single point of management—All switches in the stack are managed as
one.
Cisco Catalyst 2960-S Series are fixed-configuration, stackable, 10/10/1000
Ethernet switches, with PoE+ and non-powered versions designed for entrylevel enterprise, midmarket, and remote site networks.
• Cisco FlexStack is implemented by adding a stacking module to the
switch. This enables up to four Catalyst 2960-S series switches to be
stacked together.
• Cisco FlexStack links are full duplex 10 Gigabit Ethernet links with
recovery time between 1–2 seconds.
Cisco Catalyst 3750-X Series are fixed-port, stackable, 10/100/1000
Ethernet switches, with PoE+ and non-powered versions, that provide
enhanced resiliency through StackWise Plus and StackPower technologies.
• Cisco StackWise Plus enables up to nine Cisco Catalyst 3750 switches
to be stacked together using a 64-Gbps stack interconnect with near
subsecond failure recovery.
• Cisco StackPower shares power across the Cisco Catalyst 3750-X
switch stack. This allows the flexible arrangement of power supplies in
the stack, and enables a zero-footprint redundant power supply deployment and intelligent load shedding.
• Cisco 3750-X Series have modular uplinks and support upgrading the
Cisco IOS feature set and enhanced enterprise capabilities like TrustSec
and Medianet, to ensure that the switch functionality grows as the
organization grows.
• Built-in redundancy and high availability—The high-speed dedicated
stack connections provide redundant communication for each stack
member.
• Scalable to fit network needs—As the need for additional access
interfaces grows, adding a new switch to a stack or a module to a modular switch is easy.
The following series of Cisco Catalyst switches are used in this design when
intelligent stacking or a modular deployment is required: Cisco Catalyst
2960-S, 3750-X, and 4500E Series.
August 2012 Series
Access Layer
14
Cisco Catalyst 4500 E-Series are modular switches that support multiple
Ethernet connectivity options including 10/100/1000 Ethernet, 100-MB fiber,
gigabit fiber, and 10-gigabit fiber. The Catalyst 4500 E-Series switches also
have an upgradable supervisor module which enables future functionality
to be added with a supervisor module upgrade while maintaining the initial
investment in the chassis and the modules.
Table 1 - IP addressing for LAN deployment guide
Distribution
Block
VLAN
IP Addressing Usage
LAN Access A
100
10.4.0.x/24
Data-Access Switch 1
101
10.4.1.x/24
Voice-Access Switch 1
102
10.4.2.x/24
Data-Access Switch 2
103
10.4.3.x/24
Voice-Access Switch 2
Continue
through
114
10.4.4 - .14
alternate Data and Voice
115
10.4.15.x/25
Management
164
10.4.64.x/24
Data-Access Switch 1
165
10.4.65.x/24
Voice-Access Switch 1
166
10.4.66.x/24
Data-Access Switch 2
167
10.4.67.x/24
Voice-Access Switch 2
Continue
through
178
10.4.68 - .78
alternate Data and Voice
179
10.4.79.x/25
Management
180
10.4.80.x/24
Data-Access Switch 1
181
10.4.81.x/24
Voice-Access Switch 1
182
10.4.82.x/24
Data-Access Switch 2
183
10.4.83.x/24
Voice-Access Switch 2
Continue
through
195
10.4.84 - .94
alternate Data and Voice
179
10.4.15.x/25
Management
None
10.4.40.x
Core to Dist Links
• All key switching and forwarding components are located on the supervisor module; upgrading the supervisor upgrades the line cards.
• The Catalyst 4500 E-Series Supervisor 7L-E has uplink interfaces that
can be configured as Gigabit Ethernet or 10 Gigabit interfaces, allowing
customers to easily increase bandwidth in the future.
• The Catalyst 4500 E-Series provides maximum PoE flexibility with support of IEEE 802.3af, 802.3at, and now UPoE that supplies up to 60 watts
per port of PoE. UPoE linecards are backward compatible to earlier PoE
and PoE+ connected end points as well.
LAN Access B
• The Catalyst 4507R+E chassis supports redundant supervisor modules
and power supplies, which increases system availability by providing 1:1
redundancy for all critical systems.
• The Catalyst 4507R+E supports stateful switchover which allows a
supervisor switchover to occur with minimum disruption to the network.
• The entire software upgrade process is simplified ISSU. Not only does
ISSU help eliminate errors in the software upgrade process, but additional checks are incorporated that allow the new software version to be
tested and verified before completing the upgrade.
LAN Access C
Deployment Details
As you review the LAN Deployment Guide you may find it useful to
understand the IP addressing and VLAN assignments used. Although your
design requirements may differ, by addressing the various distribution
layers at a location with contiguous IP address space you can summarize
the IP address range to the rest of the network. This design uses VLAN
assignments that reflect the third octet of the IP address range for a given
access layer switch for ease of reference. The LAN Core IP addressing is a
combination of 30 bit subnets for point-to-point Layer 3 links, and 32 bit host
addresses for loopback addresses.
August 2012 Series
Core
Access Layer
15
Figure 11 - Stack master placement in a switch stack
Process
1. Configure the platform
k
U
in
pl
pl
in
U
Configuring the Access Layer
k
Distribution
Switch
Stack Master
2. Configure LAN switch universal settings
4. Configure client connectivity
5. Connect to distribution or WAN router
Procedure 1
Configure the platform
Some platforms require a one-time initial configuration prior to configuring
the features and services of the switch. If you do not have a platform listed in
the following steps, you can skip those steps.
Option 1. Configure the Catalyst 2960-S, 3560-X, and 3750-X
Step 1: Set the stack master switch.
switch [switch number] priority 15
When there are multiple Catalyst 2960-S or 3750-X Series switches configured in a stack, one of the switches controls the operation of the stack and
is called the stack master. When three or more switches are configured as a
stack, configure the stack master switch functionality on a switch that does
not have uplinks configured.
August 2012 Series
2092
3. Configure access switch global settings
Switch Stack
If you configure stack master switch priority on a Cisco Catalyst 2960-S
or Cisco 3750-X switch stack, a single reboot is required to force the stack
master to operate on the switch that you configured with the highest priority.
Reboot the switch stack after all of your configuration is complete for this
entire “Configuring the Access Layer” process.
Step 2: Run the stack-mac persistent timer 0 command to ensure that the
original master MAC address remains the stack MAC address after a failure.
This command does not apply to the Catalyst 3560-X switch.
stack-mac persistent timer 0
The default behavior when the stack master switch fails is for the newly
active stack master switch to assign a new stack MAC address. This new
MAC address assignment can cause the network to reconverge because the
link aggregation control protocol (LACP) and many other protocols rely on
the stack MAC address and must restart.
Access Layer
16
Step 3: To make consistent deployment of QoS easier, each platform
defines two macros that you will use in later procedures to apply the platform specific QoS configuration.
macro name AccessEdgeQoS
auto qos voip cisco-phone
@
!
macro name EgressQoS
mls qos trust dscp
queue-set 1
srr-queue bandwidth share 1 30 35 5
priority-queue out
@
Option 2. Configure the Catalyst 4507R+E platform
Step 1: To make consistent deployment of QoS easier each platform
defines two macros that you will use in later procedures to apply the platform specific QoS configuration.
class-map match-all VOIP_DATA_CLASS
match cos 5
class-map match-all VOIP_SIGNAL_CLASS
match cos 3
!
policy-map CISCOPHONE-POLICY
class VOIP_DATA_CLASS
set dscp ef
police 128k bc 8000
conform-action transmit
exceed-action drop
class VOIP_SIGNAL_CLASS
set dscp cs3
police 32k bc 8000
conform-action transmit
exceed-action drop
class class-default
set dscp default
police 10m bc 8000
August 2012 Series
conform-action transmit
exceed-action set-dscp-transmit cs1
!
class-map match-any PRIORITY-QUEUE
match dscp ef
match dscp cs5
match dscp cs4
class-map match-any CONTROL-MGMT-QUEUE
match dscp cs7
match dscp cs6
match dscp cs3
match dscp cs2
class-map match-any MULTIMEDIA-CONFERENCING-QUEUE
match dscp af41 af42 af43
class-map match-any MULTIMEDIA-STREAMING-QUEUE
match dscp af31 af32 af33
class-map match-any TRANSACTIONAL-DATA-QUEUE
match dscp af21 af22 af23
class-map match-any BULK-DATA-QUEUE
match dscp af11 af12 af13
class-map match-any SCAVENGER-QUEUE
match dscp cs1
!
policy-map 1P7Q1T
class PRIORITY-QUEUE
priority
class CONTROL-MGMT-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-CONFERENCING-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-STREAMING-QUEUE
bandwidth remaining percent 10
class TRANSACTIONAL-DATA-QUEUE
bandwidth remaining percent 10
dbl
class BULK-DATA-QUEUE
bandwidth remaining percent 4
Access Layer
17
dbl
class SCAVENGER-QUEUE
bandwidth remaining percent 1
class class-default
bandwidth remaining percent 25
dbl
!
policy-map 1P7Q1T_Access
class PRIORITY-QUEUE
priority
police cir percent 30
class CONTROL-MGMT-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-CONFERENCING-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-STREAMING-QUEUE
bandwidth remaining percent 10
class TRANSACTIONAL-DATA-QUEUE
bandwidth remaining percent 10
dbl
class BULK-DATA-QUEUE
bandwidth remaining percent 4
dbl
class SCAVENGER-QUEUE
bandwidth remaining percent 1
class class-default
bandwidth remaining percent 25
dbl
!
macro name AccessEdgeQoS
qos trust device cisco-phone
service-policy input CISCOPHONE-POLICY
service-policy output 1P7Q1T_Access
@
!
macro name EgressQoS
service-policy output 1P7Q1T
@
August 2012 Series
Step 2: When a Catalyst 4507R+E is configured with two Supervisor 7L-Es,
configure the switch to use Stateful Switchover (SSO) when moving the
primary supervisor functionality between modules. To enable a fast transparent data plane failover, SSO synchronizes active process information as
well as configuration information between supervisor modules.
redundancy
mode sso
To enable SSO mode you must have a license level of ipbase or entservices
operating on the switch supervisors. You can check the current license level
of operation with a show version command.
Procedure 2
Configure LAN switch universal settings
Within this design, there are features and services that are common across
all LAN switches, regardless of the type of platform or role in the network.
These are system settings that simplify and secure the management of the
solution.
This procedure provides examples for some of those settings. The actual
settings and values will depend on your current network configuration.
Table 2 - Common network services used in the deployment examples
Service
Address
Domain Name:
cisco.local
Active Directory, DNS, DHCP Server:
10.4.48.10
Authentication Control System:
10.4.48.15
Network Time Protocol Server:
10.4.48.17
Step 1: Configure the device hostname to make it easy to identify the
device.
hostname [hostname]
Access Layer
18
Step 2: Configure VTP transparent mode. This deployment uses VTP
transparent mode because the benefits of dynamic propagation of VLAN
information across the network are not worth the potential for unexpected
behavior that is due to operational error.
VLAN Trunking Protocol (VTP) allows network managers to configure a
VLAN in one location of the network and have that configuration dynamically
propagate out to other network devices. However, in most cases, VLANs are
defined once during switch setup with few, if any, additional modifications.
vtp mode transparent
Step 3: Enable Rapid Per-VLAN Spanning-Tree (PVST+). Rapid PVST+
provides an instance of RSTP (802.1w) per VLAN. Rapid PVST+ greatly
improves the detection of indirect failures or linkup restoration events over
classic spanning tree (802.1D).
Although this architecture is built without any Layer 2 loops, you must still
enable spanning tree. By enabling spanning tree, you ensure that if any
physical or logical loops are accidentally configured, no actual layer 2 loops
occur.
spanning-tree mode rapid-pvst
Step 4: Enable Unidirectional Link Detection (UDLD).
UDLD is a Layer 2 protocol that enables devices connected through fiberoptic or twisted-pair Ethernet cables to monitor the physical configuration
of the cables and detect when a unidirectional link exists. When UDLD
detects a unidirectional link, it disables the affected interface and alerts you.
Unidirectional links can cause a variety of problems, including spanning-tree
loops, black holes, and non-deterministic forwarding. In addition, UDLD
enables faster link failure detection and quick reconvergence of interface
trunks, especially with fiber, which can be susceptible to unidirectional
failures.
udld enable
Step 5: Set EtherChannels to use the traffic source and destination IP
address when calculating which link to send the traffic across. This normalizes the method in which traffic is load-shared across the member links
of the EtherChannel. EtherChannels are used extensively in this design
because of their resiliency capabilities.
Step 6: Configure DNS for host lookup.
At the command line of a Cisco IOS device, it is helpful to be able to type a
domain name instead of the IP address for a destination.
ip name-server 10.4.48.10
Step 7: Configure device management protocols.
Secure HTTP (HTTPS) and Secure Shell (SSH) are more secure replacements for the HTTP and Telnet protocols. They use Secure Sockets Layer
(SSL) and Transport Layer Security (TLS) to provide device authentication
and data encryption.
The SSH and HTTPS protocols enable secure management of the LAN
device. Both protocols are encrypted for privacy, and the nonsecure protocols, Telnet and HTTP, are turned off.
Specify the transport preferred none on vty lines to prevent errant connection attempts from the CLI prompt. Without this command, if the ip
name server is unreachable, long timeout delays may occur for mistyped
commands.
ip domain-name cisco.local
ip ssh version 2
no ip http server
ip http secure-server
!
line vty 0 15
transport input ssh
transport preferred none
Step 8: Enable Simple Network Management Protocol (SNMP) in order
to allow the network infrastructure devices to be managed by a Network
Management System (NMS), and then configure SNMPv2c both for a readonly and a read-write community string.
snmp-server community cisco RO
snmp-server community cisco123 RW
port-channel load-balance src-dst-ip
August 2012 Series
Access Layer
19
Step 9: If your network operational support is centralized, you can increase
network security by using an access list to limit the networks that can access
your device. In this example, only devices on the 10.4.48.0/24 network will be
able to access the device via SSH or SNMP.
access-list 55 permit 10.4.48.0 0.0.0.255
line vty 0 15
access-class 55 in
!
snmp-server community cisco RO 55
snmp-server community cisco123 RW 55
Caution
If you configure an access-list on the vty interface you may lose
the ability to use ssh to login from one router to the next for hopby-hop troubleshooting.
Step 10: Configure local login and password.
The local login account and password provides basic device access authentication to view platform operation. The enable password secures access
to the device configuration mode. By enabling password encryption, you
prevent the use of plain text passwords when viewing configuration files.
username admin password c1sco123
enable secret c1sco123
service password-encryption
aaa new-model
By default, https access to the switch will use the enable password for
authentication.
As networks scale in the number of devices to maintain, there is an operational burden to maintain local user accounts on every device. A centralized
Authentication, Authorization and Accounting (AAA) service reduces operational tasks per device and provides an audit log of user access for security
compliance and root cause analysis. When AAA is enabled for access
control, all management access to the network infrastructure devices (SSH
and HTTPS) is controlled by AAA.
TACACS+ is the primary protocol used to authenticate management
logins on the infrastructure devices to the AAA server. A local AAA user
database is also defined on each network infrastructure device to provide
a fallback authentication source in case the centralized TACACS+ server is
unavailable.
tacacs server TACACS-SERVER-1
address ipv4 10.4.48.15
key SecretKey
!
aaa group server tacacs+ TACACS-SERVERS
server name TACACS-SERVER-1
!
aaa authentication login default group TACACS-SERVERS local
aaa authorization exec default group TACACS-SERVERS local
aaa authorization console
ip http authentication aaa
Reader Tip
The AAA server used in this architecture is Cisco Authentication
Control System. Configuration of ACS is discussed in the Cisco
SBA—Borderless Networks Device Management Using ACS
Deployment Guide.
Step 11: If you want to reduce operational tasks per device, configure
centralized user authentication by using the TACACS+ protocol to authenticate management logins on the infrastructure devices to the Authentication,
Authorization and Accounting (AAA) server.
August 2012 Series
Access Layer
20
Step 12: Configure a synchronized clock by programming network devices
to synchronize to a local NTP server in the network. The local NTP server
typically references a more accurate clock feed from an outside source.
Configure console messages, logs, and debug output to provide time
stamps on output, which allows cross-referencing of events in a network.
ntp server 10.4.48.17
ntp update-calendar
!
clock timezone PST -8
clock summer-time PDT recurring
!
service timestamps debug datetime msec localtime
service timestamps log datetime msec localtime
The ntp update-calendar command configures the switch to update the
hardware clock from the ntp time source periodically. Since not all switches
have a hardware clock, this command is not supported by all devices.
Procedure 3
Configure access switch global settings
The access layer devices use VLANs to separate traffic from different
devices into the following logical networks:
• The data VLAN provides access to the network for all attached devices
other than IP Phones.
• The voice VLAN provides access to the network for IP Phones.
Both the data and the voice VLAN are configured on all user-facing
interfaces.
• The management VLAN provides in-band access to the network for the
switches management interface. The management VLAN is not configured on any user-facing interface and the VLAN interface of the switch is
the only member.
Step 1: Configure VLANs on the switch.
Configure the data, voice, and management VLANs on the switch so that
connectivity to clients, IP Phones, and the in-band management interfaces
can be configured.
vlan
name
vlan
name
vlan
name
[data vlan]
Data
[voice vlan]
Voice
[management vlan]
Management
Tech Tip
If the switch is the only switch at the site and is directly connected
to a router or firewall, do not configure a management VLAN.
Instead, configure the in-band management interface on the data
VLAN.
Step 2: Configure the switch with an IP address so that it can be managed
via in-band connectivity.
interface vlan [management vlan]
ip address [ip address] [mask]
no shutdown
ip default-gateway [default router]
Do not use the ip default-gateway command on the Catalyst 4500 because
it has IP routing enabled by default and this command will not have any
affect. Instead use the following command on the Catalyst 4500.
ip route 0.0.0.0 0.0.0.0 [default router]
Step 3: Configure DHCP snooping and enable it on the data and voice
VLANs. The switch intercepts and safeguards DHCP messages within the
VLAN. This ensures that an unauthorized DHCP server cannot serve up
addresses to end-user devices.
ip dhcp snooping vlan [data vlan],[voice vlan]
no ip dhcp snooping information option
ip dhcp snooping
August 2012 Series
Access Layer
21
Step 4: Configure ARP inspection on the data and voice VLANs.
Step 1: Configure switch interfaces to support clients and IP phones.
ip arp inspection vlan [data vlan],[voice vlan]
Step 5: Configure BPDU Guard globally to protect portfast enabled interfaces. This protects PortFast-enabled interfaces by disabling the port if
another switch is plugged into the port.
spanning-tree portfast bpduguard default
BPDU guard protects against a user plugging a switch into an access port,
which could cause a catastrophic undetected spanning-tree loop.
If a portfast configured interface receives a BPDU, an invalid configuration
exists, such as the connection of an unauthorized device. The BPDU guard
feature prevents loops by moving a nontrunking interface into an errdisable
state when a BPDU is received on an interface when portfast is enabled.
Figure 12 - Scenario that BPDU Guard protects against
Loop caused by mis-cabling the switch
2093
Cisco SBA
Access-Layer
Switch
interface range [interface type] [port number]–[port number]
switchport access vlan [data vlan]
switchport voice vlan [voice vlan]
Step 2: Because only end-device connectivity is provided at the access
layer enable PortFast. PortFast shortens the time it takes for the interface to
go into a forwarding state by disabling 802.1q trunking, and channel group
negotiation.
switchport host
Step 3: Enable QoS by applying the access edge QoS macro that was
defined in the platform configuration procedure.
macro apply AccessEdgeQoS
Spanning tree doesn’t detect the
loop because PortFast is enabled
User-Installed
Low-End Switch
The host interface configurations support PCs, phones, or wireless access points.
Inline power is available on switches that support 802.3AF/AT for capable devices.
All client facing interfaces allow for an untrusted PC and/or a trusted Cisco
IP phone to be connected to the switch and automatically set QoS parameters. When a Cisco Phone is connected, trust is extended to the phone,
and any device that connects to the phone will be considered untrusted and
all traffic from that device will be remarked to best-effort or class of service
(CoS) 0.
Next, configure port security on the interface.
Procedure 4
Configure client connectivity
To make configuration easier when the same configuration will be applied
to multiple interfaces on the switch, use the interface range command. This
command allows you to issue a command once and have it apply to many
interfaces at the same time. Since most of the interfaces in the access layer
are configured identically, it can save a lot of time. For example, the following
command allows you to enter commands on all 24 interfaces (Gig 0/1 to Gig
0/24) simultaneously.
interface range Gigabitethernet 0/1-24
Step 4: Configure 11 MAC addresses to be active on the interface at one
time; additional MAC addresses are considered to be in violation, and their
traffic will be dropped.
switchport port-security maximum 11
switchport port-security
The number of MAC addresses allowed on each interface is specific to the
organization. However, the popularity of virtualization applications, IP phones,
and passive hubs on the desktop drives the need for the number to be larger
than one might guess at first glance. This design uses a number that allows
flexibility in the organization while still protecting the network infrastructure.
Step 5: Set an aging time to remove learned MAC addresses from the
secured list after 2 minutes of inactivity.
switchport port-security aging time 2
switchport port-security aging type inactivity
August 2012 Series
Access Layer
22
switchport port-security violation restrict
Step 7: Configure DHCP snooping and ARP inspection on the interface to
process 100 packets per second of traffic on the port.
ip arp inspection limit rate 100
ip dhcp snooping limit rate 100
Step 8: Configure IP Source Guard on the interface. IP Source Guard is a
means of preventing IP spoofing.
ip verify source
The Catalyst 4500 does not support the ip verify source command. Instead,
use the following command:
ip verify source vlan dhcp-snooping
VLAN 100
Data VLAN
VLAN 101
Voice VLAN
IP: 10.4.15.5/25
VLAN 115
Management VLAN
vlan 100
name Data
vlan 101
name Voice
vlan 115
name Management
!
interface vlan 115
description in-band management
ip address 10.4.15.5 255.255.255.128
no shutdown
!
August 2012 Series
LAN
Distribution
Switch
2094
Example: Connected to distribution layer
ip default-gateway 10.4.15.1
!
ip dhcp snooping vlan 100,101
no ip dhcp snooping information option
ip dhcp snooping
ip arp inspection vlan 100,101
!
spanning-tree portfast bpduguard default
!
interface range GigabitEthernet 1/0/1–24
switchport access vlan 100
switchport voice vlan 101
switchport host
macro apply AccessEdgeQoS
switchport port-security maximum 11
switchport port-security
switchport port-security aging time 2
switchport port-security aging type inactivity
switchport port-security violation restrict
ip arp inspection limit rate 100
ip dhcp snooping limit rate 100
ip verify source
Example: Connected to WAN Router
VLAN 64
Wired
Data VLAN
VLAN 69
Wired
Voice VLAN
IP: 10.5.64.5/24
VLAN 64
Management VLAN
Remote Site
WAN Router
vlan 64
name WiredData
vlan 69
name WiredVoice
!
interface vlan 69
description in-band managementto WAN Router
Access Layer
23
2095
Step 6: Configure the restrict option to drop traffic from MAC addresses
that are in violation, but do not shut down the port. This configuration
ensures that an IP phone can still function on this interface when there is a
port security violation.
Procedure 5
Connect to distribution or WAN router
Access layer devices can be one component of a larger LAN and connect to
a distribution switch, or, in the case of a small remote site, might be the only
LAN device and connect directly to a WAN device. Unless the access layer
device is a single fixed configuration switch connecting to a WAN router,
Layer 2 EtherChannels are used to interconnect the devices in the most
resilient method possible.
August 2012 Series
The physical interfaces that are members of a Layer 2 EtherChannel are
configured prior to configuring the logical port-channel Interface. This
allows for minimal configuration because most of the commands entered to
a port-channel interface are copied to its members’ interfaces and do not
require manual replication.
Figure 13 - EtherChannel example
Distribution
Switch
Logical
PortChannel
Interface
2096
r
be e
c
em fa
M ter
In
!
ip default-gateway 10.5.69.1
!
ip dhcp snooping vlan 64,69
no ip dhcp snooping information option
ip dhcp snooping
ip arp inspection vlan 64,69
!
spanning-tree portfast bpduguard default
!
interface range GigabitEthernet 1/0/1–24
switchport access vlan 64
switchport voice vlan 69
switchport host
macro apply AccessEdgeQoS
switchport port-security maximum 11
switchport port-security
switchport port-security aging time 2
switchport port-security aging type inactivity
switchport port-security violation restrict
ip arp inspection limit rate 100
ip dhcp snooping limit rate 100
ip verify source
When using EtherChannel, the member interfaces should be on different
switches in the stack or different modules in the modular switch for the
highest resiliency.
M
In em
te b
rfa e
ce r
ip address 10.5.69.5 255.255.255.0
no shutdown
Switch Stack
Configure two or more physical interfaces to be members of the
EtherChannel. It is recommended that they are added in multiples of two.
This procedure details how to connect any Cisco SBA access layer switch
(Cisco Catalyst 4500, 3750-X, 3560-X, or 2960-S) to a distribution switch or
WAN router. Where there are differences for configuring a specific switch it
will be called out in the step.
Option 1. Configure EtherChannel to distribution switch
Step 1: Configure EtherChannel member interfaces.
When connecting to another switch set Link Aggregation Control Protocol
negotiation to active on both sides to ensure a proper EtherChannel is
formed. Also, apply the egress QoS macro that was defined in the platform
configuration procedure to ensure traffic is prioritized appropriately.
Access Layer
24
An 802.1Q trunk is used for the connection to this upstream device, which
allows the uplink to provide Layer 3 services to all the VLANs defined on
the access layer switch. Prune the VLANs allowed on the trunk to only the
VLANs that are active on the access switch. Set DHCP Snooping and ARP
Inspection to trust. When using EtherChannel the interface type will be portchannel and the number must match channel-group configured in Step 1.
The Catalyst 3750 requires the switchport trunk encapsulation dot1q
command.
interface [interface type] [number]
description EtherChannel link to Distribution Layer
switchport trunk allowed vlan [data vlan],[voice vlan],
[mgmt vlan]
switchport mode trunk
ip arp inspection trust
ip dhcp snooping trust
logging event link-status
logging event trunk-status
no shutdown
If the interface type is not a port-channel, you must configure an additional
command macro apply EgressQoS on the interface.
August 2012 Series
Figure 14 - VLAN hopping attack
Attacker
802.1Q Trunk
VLAN A
VLAN B
Data
802.1Q Trunk with
Native VLAN A
Access
Interface
VLAN B
Host
VLAN B
Data
Data
2097
Step 2: Configure the trunk.
There is a remote possibility that an attacker can create a double 802.1Q
encapsulated packet. If the attacker has specific knowledge of the 802.1Q
native VLAN, a packet could be crafted that when processed, the first or
outermost tag is removed when the packet is switched onto the untagged
native VLAN. When the packet reaches the target switch, the inner or second tag is then processed and the potentially malicious packet is switched
to the target VLAN.
802.1Q Tag
interface [interface type] [port 1]
description Link to Distribution Layer port 1
interface [interface type] [port 2]
description Link to Distribution Layer port 2
!
interface range [interface type] [port 1], [interface type]
[port 2]
switchport
macro apply EgressQoS
channel-protocol lacp
channel-group [number] mode active
logging event link-status
logging event trunk-status
logging event bundle-status
Next, mitigate VLAN hopping on the trunk for switch-to-switch connections.
802.1Q Tags
Cisco Catalyst 2960S does not require the switchport command.
At first glance, this appears to be a serious risk. However, the traffic in this
attack scenario is in a single direction and no return traffic can be switched
by this mechanism. Additionally, this attack cannot work unless the attacker
knows the native VLAN ID.
Step 3: To remove the remote risk of this type of attack,, configure an
unused VLAN on all switch-to-switch 802.1Q trunk links from access layer to
distribution layer. Using a hard to guess, unused VLAN for the native VLAN
reduces the possibility that a double 802.1Q-tagged packet can hop VLANs.
If you are running the recommended EtherChannel uplink to the LAN access
layer switch, configure the switchport trunk native vlan on the port-channel
interface.
vlan 999
!
interface [port-channel] [number]
switchport trunk native vlan 999
Access Layer
25
Step 4: Save the running configuration that you have entered so it will
be used as the startup configuration file when your switch is rebooted or
power-cycled.
copy running-config startup-config
Step 5: If you have configured your access-layer Cisco Catalyst 2960-S or
Cisco Catalyst 3750-X switch stack for an EtherChannel link to the distribution layer switch, reboot your switch stack now to ensure proper operation
of EtherChannel. A single reboot of a newly configured switch is necessary
to ensure that EtherChannel operates with other features configured on the
switch stack.
reboot
Option 2. Configure EtherChannel to WAN router
If your access layer switch is a single fixed configuration switch connecting
to a single remote-site router without using EtherChannel you can skip Step
1. If you have a remote-site with dual routers for resilience, see the Cisco
SBA—Borderless Networks WAN Deployment Guide for configuration
guidance for the access layer uplinks.
Step 1: Configure EtherChannel member interfaces.
When connecting to a network infrastructure device that does not support
LACP, like a router, set the channel-group mode to forced on.
Also, apply the egress QoS macro that was defined in the platform configuration procedure to ensure traffic is prioritized appropriately.
Cisco Catalyst 2960S does not require the switchport command.
interface [interface type] [port 1]
description Link to Router port 1
interface [interface type] [port 2]
description Link to Router port 2
!
interface range [interface type] [port 1], [interface type]
[port 2]
switchport
macro apply EgressQoS
channel-group [number] mode on
logging event link-status
logging event trunk-status
logging event bundle-status
August 2012 Series
Step 2: Configure the trunk.
An 802.1Q trunk is used for the connection to this upstream device, which
allows the router to provide Layer 3 services to all the VLANs defined on
the access layer switch. Prune the VLANs allowed on the trunk to only the
VLANs that are active on the access switch. Set DHCP snooping and ARP
Inspection to trust. When using EtherChannel, the interface type will be
port-channel, and the number must match channel-group configured in
Step 1 in Option 2: of this procedure.
The Catalyst 3750 requires the switchport trunk encapsulation dot1q
command.
interface [interface type] [number]
description EtherChannel link to Router
switchport trunk allowed vlan [data vlan],[voice vlan]
switchport mode trunk
ip arp inspection trust
ip dhcp snooping trust
spanning-tree portfast trunk
logging event link-status
logging event trunk-status
no shutdown
If the interface type is not a port-channel, you must configure additional
commands switchport and macro apply EgressQoS on the interface.
Step 3: Save the running configuration that you have entered so it will
be used as the startup configuration file when your switch is rebooted or
power-cycled.
copy running-config startup-config
Step 4: If you have configured your access layer Cisco Catalyst 2960-S
or Cisco Catalyst 3750-X switch stack for EtherChannel to the WAN router,
reboot your switch stack now to ensure proper operation of EtherChannel.
A single reboot of a newly configured switch is necessary to ensure that
EtherChannel operates with other features configured on the switch stack.
reboot
Access Layer
26
Figure 15 - Configuration Example Procedure 5 Option 1
Figure 16 - Configuration Example Procedure 5 Option 2
802.1Q Trunk
VLANs 100,101,115
Native VLAN 999
VLAN 115
Management
VLAN
LAN
Distribution
Switch
vlan 999
!
interface GigabitEthernet 1/0/25
description Link to Distribution Layer port 1
interface GigabitEthernet 3/0/25
description Link to Distribution Layer port 2
!
interface range GigabitEthernet 1/0/25, GigabitEthernet 3/0/25
macro apply EgressQoS
logging event link-status
logging event trunk-status
logging event bundle-status
channel-protocol lacp
channel-group 1 mode active
!
interface Port-channel 1
description Etherchannel to Distribution Layer
switchport trunk encapsulation dot1q
switchport trunk native vlan 999
switchport trunk allowed vlan 100,101,115
switchport mode trunk
ip arp inspection trust
ip dhcp snooping trust
no shutdown
August 2012 Series
VLAN 69
Wired Voice
VLAN
VLAN 64
Management
Interface
Remote Site
WAN Router
interface GigabitEthernet 1/0/24
description Link to WAN Router
macro apply EgressQoS
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 64,69
switchport mode trunk
ip arp inspection trust
ip dhcp snooping trust
spanning-tree portfast trunk
no shutdown
Access Layer
27
2100
VLAN 101
Voice VLAN
VLAN 64
Wired Data
VLAN
2099
VLAN 100
Data VLAN
802.1Q Trunk
VLANs 64, 69
Figure 17 - Configuration Example Procedure 5 Option 2 with EtherChannel
802.1Q Trunk
VLAN 64
Wired Data
VLAN
VLAN 69
Wired Voice
VLAN
VLAN 64
Management
Interface
Remote Site
WAN Router
2101
VLANs 64, 69
interface GigabitEthernet 1/0/25
description Link to WAN Router port 1
interface GigabitEthernet 3/0/25
description Link to WAN Router port 2
!
interface range GigabitEthernet 1/0/25, GigabitEthernet 3/0/25
macro apply EgressQoS
logging event link-status
logging event trunk-status
logging event bundle-status
channel-group 1 mode on
!
interface Port-channel 1
description EtherChannel to WAN Router
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 64,69
switchport mode trunk
ip arp inspection trust
ip dhcp snooping trust
spanning-tree portfast trunk
no shutdown
August 2012 Series
Access Layer
28
Distribution Layer
Business Overview
Technology Overview
The challenge for an organization to deliver reliable employee access to
business services grows as the number of employees at a given location
expands. As the number of access layer closets at a location grows, it
creates the need to aggregate the connectivity at a common point. One of
the benefits of aggregation is that you can reduce costs by reducing the
number of interconnections from each access layer switch to the rest of the
network, which is used to get to the applications and resources hosted in the
center of the network or across the WAN.
The primary function of the distribution layer is to aggregate access layer
switches in a given building or campus. The distribution layer provides a
boundary between the Layer 2 domain of the access layer and the Layer
3 domain that provides a path to the rest of the network. This boundary
provides two key functions for the LAN. On the Layer 2 side the distribution
layer creates a boundary for Spanning Tree Protocol limiting propagation of
Layer 2 faults. On the Layer 3 side the distribution layer provides a logical
point to summarize IP routing information before it enters the network and
reduce IP route tables for easier troubleshooting and faster recovery from
failures.
Traditional network design used parallel physical networks to transport
different traffic types like voice or data, or to transport traffic with different
security needs. To reduce costs IT organizations must create a single multiuse network infrastructure that can use multiple VLANs on a single physical
infrastructure. The dominant internetwork protocol in use in networks
today is IP, which allows a routed network topology, but some applications
require that network connected endpoints be Layer 2 adjacent. IT must
work to design networks that accommodate the application requirements
without sacrificing the reliability or scalability of the network. The goal of
the network foundation architecture is to provide a design that supports an
ever-increasing number of services required from the LAN and to control
the increasing complexity of delivering those services without eliminating
essential functionality.
August 2012 Series
The Cisco SBA LAN distribution layer uses a simplified distribution layer
design that is easier to operate and troubleshoot than the traditional and
routed access designs.
Distribution Layer
29
Figure 18 - Distribution layer overview
Core
Switches
Distribution
Switches
Building 1
August 2012 Series
Building 2
Building 3
2102
Client Access Switches
Building 4
Distribution Layer
30
Figure 19 - Traditional loop-free design with a VLAN per access switch
Traditional LAN designs deploy a multitier approach with Layer 2 from the
access layer to the distribution layer, where the Layer 3 boundary exists.
The connectivity from the access layer to the distribution layer can result in
either a loop-free or looped design.
Layer-3 Link
30
VLAN 30
VLAN 40
AN
VL
2103
40
Figure 20 - Traditional looped design with VLANs spanning access switches
AN
30
VLAN 30
VLAN 30
AN
VL
30
VLAN 30
All of these redundancy protocols require that you fine tune the default
settings to allow for subsecond network convergence.
Some organizations require the same Layer 2 VLAN be extended to multiple
access layer closets to accommodate an application or service. The looped
design causes spanning tree to block links, which reduces the bandwidth
from the rest of the network and can cause slower network convergence.
AN
To create a resilient IP gateway for VLANs in this design, you must use
first-hop redundancy protocols, which provide hosts with a gateway IP
for a VLAN on a healthy switch. Hot Standby Routing Protocol (HSRP) and
Virtual Router Redundancy Protocol (VRRP) are the most common gateway
redundancy protocols, but they only allow hosts to send data out one of the
access uplinks to the distribution layer. Gateway Load Balancing Protocol
(GLBP) does provide greater uplink utilization for traffic exiting the access
layer by balancing load from hosts across multiple uplinks, but you can only
use it in a non-looped topology.
VL
In the traditional network design, the distribution layer has two standalone
switches for resiliency. It is recommended that you restrict a Layer 2 VLAN
to a single wiring closet or access uplink pair to reduce or eliminate topology
loops that Spanning Tree Protocol must block and that are a common point
of failure in LANs. Restricting a VLAN to a single switch provides a loop-free
design, but it does limit network flexibility.
VL
Traditional Distribution Layer Design
Interface
Blocked
2104
Interface
Blocked
August 2012 Series
Distribution Layer
31
Routed Access Distribution Layer Design
The distribution layer design in the Cisco SBA LAN design uses multiple
physical switches that act as a single logical switch or a single, highlyredundant physical switch. One advantage of this design is that spanning
tree dependence is minimized, and all uplinks from the access layer to the
distribution are active and passing traffic. Even in the distributed VLAN
design, spanning tree blocked links due to looped topologies are eliminated.
You reduce dependence on spanning tree by using EtherChannel to the
access layer with dual-homed uplinks. This is a key characteristic of this
design and you can load balance up to eight links if needed for additional
bandwidth.
AN
2105
VL
0
N4
A
VL
30
Figure 21 - Simplified design with a VLAN per access switch
AN
3
2106
VL
30
Simplified Distribution Layer Design
AN
The challenge with the routed access layer design is that the Layer 2
domains are confined to a single access closet, which limits flexibility for
applications that require Layer 2 connectivity that extends across multiple
access closets.
VL
In another approach to access and distribution layer design, you can use
Layer 3 all the way to the access layer. The benefits of this design are that
you eliminate spanning tree loops and reduce protocols because the IP
gateway is now the access switch. Because there are no spanning tree
blocking links, you can use both uplinks to the access layer and increase
effective bandwidth available to the users.
0
Figure 22 - Simplified design with VLANs spanning access switches
EtherChannel is a logical interface that can use a control plane protocol to
manage the physical members of the bundle. It is better to run a channel
protocol instead of using forced-on mode because a channel protocol
performs consistency checks for interfaces programmed to be in the channel and provides protection to the system from inconsistent configurations.
Cisco Catalyst switches provide both Port Aggregation Protocol (PAgP),
which is a widely deployed Cisco designed protocol, and Link Aggregation
Protocol (LACP) based on IEEE 802.3ad. This design uses LACP for
EtherChannel because it is the only protocol supported in a Catalyst 3750
cross-stack configuration and can be used in all configurations in this
design.
There are several other advantages to the simplified distribution layer
design. You no longer need IP gateway redundancy protocols like HSRP,
VRRP, and GLBP because the default IP gateway is now on a single logical interface and resiliency is provided by the distribution layer switch or
switches. Also, the network will converge faster now that it is not depending on spanning tree to unblock links when a failure occurs because
EtherChannel provides fast subsecond failover between links in an uplink
bundle.
The topology of the network from the distribution layer to the access layer
is logically a hub-and-spoke topology, which reduces complexity of design
and troubleshooting. The hub-and-spoke topology design provides a more
efficient operation for IP Multicast in the distribution layer because there is
now a single logical designated router to forward IP Multicast packets to a
given VLAN in the access layer.
Finally, by using the single logical distribution layer design, there are fewer
boxes to manage, which reduces the amount of time spent on ongoing
provisioning and maintenance.
August 2012 Series
Distribution Layer
32
Distribution Layer Roles
Figure 23 - Two tier Collapsed LAN Core design
Much emphasis has been placed on the distribution layer as the access
layer aggregation point because this is the most common role. The distribution layer serves other roles in the SBA LAN deployments.
In many smaller locations, the WAN head end and Internet Edge terminate at
the headquarters location, along with a server farm or small data center and
the LAN access for user connectivity. In these situations a single distribution
layer or “collapsed Core” design may be appropriate to allow the network to
stay within budget limits while serving a smaller LAN access environment.
Although the port density and configuration complexity may not be an issue,
operational complexity of supporting many functions on one device must be
monitored as the organization grows.
Servers
Firewall
Switch
Stack
Cisco ACE
Server
Room
Wireless
LAN Controller
WAN
Routers
WAN
Distribution
Switch
Collapsed
LAN Core
Firewall
Internet
Client
Access
Switches
August 2012 Series
2086
LAN
Access
Distribution Layer
33
In larger LAN locations where the access layer density along with the number of network-service devices and WAN routers exceeds platform density
or operational complexity additional distribution layer modules can break up
the design.
The addition of a separate “services” distribution layer provides:
• Modular growth for high densities of WAN headend routers and WAN
services like WAAS appliance.
• Wireless LAN controller termination in a central location for larger
campus populations.
• Fault domains separate from the LAN access for a more resilient overall
network.
• IP address summarization from WAN or Internet Edge toward the core of
the network.
Figure 24 - Network services distribution layer
LAN
Core
Wireless
LAN Controller
LAN
Distribution
Layer
Network Services
Distribution Layer
Firewall
Client
Access
Switches
You can use multiple platforms to deploy the simplified distribution layer
design. Physically, the distribution layer can be a Cisco Catalyst 6500 Virtual
Switching System (VSS) 4T, a highly available Cisco Catalyst 4507R+E
switch, or a stack of Cisco Catalyst 3750-X switches. It is important to note
that although each switch has different physical characteristics, each
appears to the rest of the network as a single node and provides a fully
resilient design.
Cisco Catalyst 6500 VSS 4T
• Cisco Catalyst 6500 VSS 4T uses Cisco Catalyst 6500 Supervisor
Engine 2T, which increases the per slot switching capacity to 80 Gbps,
delivers better scalability, and provides enhanced hardware-enabled
features. The increased performance enables the system to provide
40-gigabit Ethernet uplinks for core layer connectivity.
• Cisco 6500 Supervisor 2T supports the line cards enabled for Policy
Feature Card 4 (PFC4), including the WS-X6816-10G WS-X6908-10G
and WS-X6904-40G-2T, which provide enhanced capabilities. The
WS-X6908-10G provides eight 10Gb Ethernet ports with 1:1 oversubscription. The WS-X6904-40G-2T provides up to four 40Gb Ethernet
ports or up to sixteen 10Gb Ethernet ports using modular adapters for
10Gb or 40Gb Ethernet applications and can be programmed to run in
2:1 or 1:1 oversubscription mode. The existing WS-X6724 and WS-X6748
based gigabit Ethernet fiber optic cards are supported in CFC mode or
the newer WS-X6824 and WS-X6848 PFC4-based cards.
• The Supervisor 2T-based switch enhances support for Cisco TrustSec
(CTS) by providing MacSec encryption and role-based access control
(RBAC) lists, and delivers improved control plane policing to address
denial-of-service attacks.
Internet
2087
WAN
Whether the distribution layer role in your network design is serving as
purely LAN access aggregation, a collapsed Core, or network-services
aggregation, the Cisco SBA distribution layer configuration provides the processes and procedures to prepare this layer of the LAN for your application.
August 2012 Series
Distribution Layer Platforms
• Effectively allows the clustering of two physical chassis into a logical
entity that can be operated as a single device. This configuration provides redundant chassis, supervisors, line cards, and power supplies
and can provide the highest density of the product options for Gigabit
Ethernet, 10 Gigabit Ethernet, and now 40 Gigabit Ethernet EtherChannel
uplinks using Cisco Multi-chassis EtherChannel.
• Provides stateful switchover between supervisors in each chassis for
Nonstop Forwarding in the event of a failure and provides Enhanced Fast
Software Upgrades for minimizing downtime for upgrades.
Distribution Layer
34
• The premier distribution layer platform in this design. It allows for high
density aggregation of Gigabit Ethernet and 10 Gigabit Ethernet connected wiring closets, while providing an advanced feature set and the
highest resiliency of the available platforms.
Cisco Catalyst 4507R+E Switch
• Cisco Catalyst 4507R+E switch has redundant supervisors, line cards,
and power supplies. In this design, Cisco uses a single 4507R+E chassis
configured with resilient components as a distribution layer platform.
The Supervisor 7E has the ability to provide a medium density of Gigabit
Ethernet and even 10 Gigabit Ethernet EtherChannel links to the access
layer.
• Provides stateful switchover which is critical to Nonstop Forwarding in the
event of a failure and allows in-service software upgrades for the system.
• Use it at locations where there is only a small number of Gigabit
Ethernet or 10 Gigabit Ethernet connected wiring closets that need to be
aggregated.
Cisco Catalyst 3750-X Stack
• Configured as a single unit, but has independent load-sharing power
supplies and processor for each switch in the StackWise Plus stack.
The Cisco SBA LAN architecture uses a pair of stacked 3750X-12S-E
switches that provide Layer 2 and Layer 3 switching. The switches use
Small Form-Factor Pluggable (SFP) transceivers for a port-by-port
option of copper or fiber optic Gigabit Ethernet EtherChannel uplinks to
access closets.
• Cisco StackWise Plus enables up to nine Cisco Catalyst 3750-X
switches to be stacked together using a 64-Gbps stack interconnect
with near subsecond failure recovery.
• Cisco StackPower shares power across the Cisco Catalyst 3750-X
switch stack. This allows the flexible arrangement of power supplies in
the stack, and enables a zero-footprint redundant power supply deployment and intelligent load shedding.
• Cisco 3750-X Series have modular uplinks for connectivity to the core
layer at Gigabit or 10 Gigabit Ethernet speeds, and support upgrading
the IOS feature set and enhanced enterprise capabilities like TrustSec
and Medianet, to ensure that the switch functionality grows as the
organization grows.
• Use it at locations where there is only a small number of gigabit connected wiring closets that need to be aggregated.
August 2012 Series
Deployment Details
The single, logical, resilient, distribution-layer design simplifies the distribution switch configuration over traditional dual system designs.
Process
Configuring the Distribution Layer
1. Configure the platform
2. Configure LAN switch universal settings
3. Configure distribution global settings
4. Configure IP unicast routing
5. Configure IP Multicast routing
6. Configure IP Multicast RP
7. Connect to access layer
8. Connect to LAN core or WAN router
Procedure 1
Configure the platform
Some platforms require a one-time initial configuration prior to configuring
the features and services of the switch. If you do not have a platform listed in
the following steps, you can skip those steps.
Option 1. Configure Cisco Catalyst 6500 Virtual Switching System 4T
Cisco Catalyst 6500 Virtual Switching System 4T clusters two physical 6500
switches with a single Supervisor 2T in each switch together as a single logical switch. One of the supervisors acts as the active control plane for both
chassis by controlling protocols such as EIGRP, Spanning Tree, CDP, and so
forth, while both supervisors actively switch packets in each chassis.
The following configuration example shows you how to convert two standalone Cisco Catalyst 6500 switches to a Virtual Switching System (VSS). If
you are migrating your switches from an existing in-service dual chassis role
Distribution Layer
35
to a VSS system, go to www.cisco.com and search on “Migrate Standalone
Cisco Catalyst 6500 Switch to Cisco Catalyst 6500 Virtual Switching
System” for information that describes how to do this migration. For an
in-depth VSS configuration guide and configuration options, go to www.
cisco.com and search for the Campus 3.0 Virtual Switching System Design
Guide.
When you set up the Cisco Catalyst 6500 Virtual Switching System 4T, connect two 10 Gigabit Ethernet links between the chassis to provide the Virtual
Switch Link (VSL). Use at least two links. However, there are restrictions on
which 10 Gigabit Ethernet interfaces you can use for the VSL. This design
uses the two 10 Gigabit Ethernet interfaces on each supervisor. You must
cable the interfaces together before you can configure the VSS.
This design uses IOS 15.0(1)SY1 with the IP Services Feature Set for all
configuration examples.
Step 1: Convert standalone 6500s to VSS.
Configure a hostname on each switch so you can keep track of your programming steps.
On the Catalyst 6500 standalone switch #1:
Router#config t
Router#(config)#hostname VSS-Sw1
On the Catalyst 6500 standalone switch #2:
Router#config t
Router#(config)#hostname VSS-Sw2
On the standalone switch #1:
VSS-Sw1(config)#switch virtual domain 100
VSS-Sw1(config-vs-domain)# switch 1
On the standalone switch #2:
VSS-Sw2(config)#switch virtual domain 100
VSS-Sw2(config-vs-domain)# switch 2
Step 2: Configure the Virtual Switch Link (VSL).
The VSL is a critical component of the Virtual Switching System. Use unique
port-channel numbers on each switch even though they connect to each
other because both switches will soon become a single logical switch.
This example uses port-channel number 101 on switch 1 and port-channel
number 102 on switch 2. You must configure channel-group mode on for
the VSL port channel. For the physical interfaces of the VSL EtherChannel,
this example uses the 10 Gigabit Ethernet interfaces on the supervisor.
On standalone switch #1:
VSS-Sw1(config)#interface port-channel 101
VSS-Sw1(config-if)#switch virtual link 1
VSS-Sw1(config-if)#no shutdown
VSS-Sw1(config)#interface range tengigabit 5/4-5
VSS-Sw1(config-if)#channel-group 101 mode on
VSS-Sw1(config-if)#no shutdown
On standalone switch #2:
Each VSS switch pair must have a unique domain assigned that the pair
shares. In this example, the domain number is 100. Each switch is also given
a unique number in the domain, switch 1 or switch 2.
Figure 25 - VSS domain
Virtual Switch Domain 100
VSS-Sw2(config)#interface port-channel 102
VSS-Sw2(config-if)#switch virtual link 2
VSS-Sw2(config-if)#no shutdown
VSS-Sw2(config)#interface range tengigabit 5/4-5
VSS-Sw2(config-if)#channel-group 102 mode on
VSS-Sw2(config-if)#no shutdown
Switch #1
August 2012 Series
Switch #2
2107
VSL 10GbE
EtherChannel
Distribution Layer
36
At this point you should be able to see that port-channel 101 and 102 are up,
and both links are active on standalone switch #1 and standalone switch #2
respectively. The switches are not in VSS mode yet.
VSS-Sw1# show etherchannel 101 port
VSS-Sw2# show etherchannel 102 port
Ports in the group:
------------------Port: Te5/4
-----------Port state = Up Mstr In-Bndl
Port: Te5/5
-----------Port state = Up Mstr In-Bndl
Step 3: Enable virtual mode operation.
Now that a port-channel has been established between the switches,
convert each switch to virtual mode operation. At the enable prompt (that is,
not in configuration mode) on each switch, enter the following commands for
each switch.
On standalone switch #1:
VSS-Sw1# switch convert mode virtual
On standalone switch #2:
VSS-Sw2# switch convert mode virtual
When asked if you want to proceed, answer yes.
Each switch now renumbers its interfaces from interface y/z (where y is
the slot number and z is the interface number) to interface x/y/z (where x
is the switch number, y is the module number in that switch, and z is the
interface on that module). This numbering scheme allows the two chassis to
be addressed and configured as a single system from a single supervisor,
which is the supervisor with the active control plane.
Once the configuration changes, it prompts you to save the configuration
to bootflash. Press Return <CR> or Enter to accept the destination filename
and location on each switch.
Both switches reload and become a VSS and one of the switches is resolved
as the ACTIVE supervisor for the VSS cluster. All configuration commands
now must be entered on the single active switch console; the standby switch
console displays the Standby prompt.
August 2012 Series
Use the following command to verify that both switches can see each other,
that they are in SSO mode, and that the second supervisor is in standby hot
status.
VSS-Sw1#show switch virtual redundancy
To recognize that the two Catalyst 6500 switches are now operating as a
single VSS system, rename the switch hostname.
VSS-Sw1(config)#hostname 6500VSS
6500VSS(config)#
Step 4: Configure dual-active detection mechanism.
A critical aspect of the Cisco Catalyst 6500 VSS 4T is the control plane
and data plane operating models. From a control plane standpoint the VSS
uses an active-standby operating model. This means that one supervisor
becomes the active control plane for the entire VSS while the other supervisor becomes the standby. The control plane handles protocol operations
like EIGRP peering, route table updates, and spanning tree BPDUs. On the
dataplane side, both supervisors are actively forwarding traffic in an activeactive operating model. The VSL allows the supervisors to communicate
and stay in synchronization. The VSS uses the Stateful Switchover (SSO)
redundancy facility to keep the controlplane synchronized between the two
supervisors.
In the event that the VSL is severed (that is, all links), or for any other reason
communication is lost over the VSL, both supervisors would assume the
active control plane role is creating a dual-active condition which can result
in network instability.
To prevent the dual-active scenario from causing an outage in the network,
VSS supports multiple different dual-active detection mechanisms. The
dual-active detection mechanisms are used to trigger a VSS recovery
mode. In the VSS recovery mode only one supervisor is allowed to remain
active, the other supervisor which is in recovery mode, shuts down all of
its’ interfaces except the VSL interfaces, thereby preventing instability in
the network. Once the VSL is repaired, and communication over the VSL
is reestablished, then the VSS would reboot the supervisor that was in the
recovery mode and return the VSS to a normal operating state.
You can use the following methods to detect this dual-active condition:
• Ethernet Fast-Hello (VSLP) packet mode link
• Enhanced Port Aggregation Protocol (PAgP) hellos between an adjacent
switch to the VSS
Distribution Layer
37
This design uses the Fast-Hello (VSLP) packet mode link for dual-active
detection. To configure the link, use a Gigabit Ethernet interface on each
VSS switch chassis and cable them together (similar to a VSL link) in a backto-back fashion. This link does not require high bandwidth because it is only
a detection link with control plane hellos on it.
Figure 26 - VSLP
Hot
Standby
6500-VSS(config)# switch virtual domain 100
6500-VSS(config-vs-domain)#dual-active detection fast-hello
6500-VSS(config)#interface range gigabit1/1/8, gigabit2/1/8
6500-VSS(config-if-range)#dual-active fast-hello
6500-VSS(config-if-range)#no shutdown
*Feb 25 14:28:39.294: %VSDA-SW2_SPSTBY-5-LINK_UP: Interface
Gi2/1/8 is now dual-active detection capable
*Feb 25 14:28:39.323: %VSDA-SW1_SP-5-LINK_UP: Interface
Gi1/1/8 is now dual-active detection capable
Step 5: Configure the system virtual MAC address.
By default, the VSS system uses the default chassis-based MAC-address
pool assigned to the switch that is resolved to be the active switch when
the switches initialize. Set a virtual MAC address for the VSS system so that
either active supervisor will use the same MAC address pool, regardless of
which supervisor is active, even across a system reboot.
6500-VSS(config)# switch virtual domain 100
6500-VSS(config-vs-domain)# mac-address use-virtual
Configured Router mac address is different from operational
value. Change will take effect after config is saved and
the entire Virtual Switching System (Active and Standby) is
reloaded.
August 2012 Series
copy running-config startup-config
reload
Step 7: Configure QoS.
2108
VSLP Dual-Active
Detect Link
Save the running configuration and then reload the entire system (both
chassis).
When the switches initialize after this final reload, the VSS programming is
complete.
VSL 10GbE
EtherChannel
Active
Step 6: Save and reload the switch.
On the Catalyst 6500 Supervisor 2T based switches, QoS is enabled
by default and policies for interface queuing are defined by attached
service policies. The QoS policies are now defined using Cisco Common
Classification Policy Language (C3PL) which is similar to Modular QoS CLI
to reduce operational complexity.
All interface connections in the distribution and core are set to trust differentiated services code point (DSCP). Even though this design is configured to
trust DSCP markings, it is a best practice to ensure proper mapping of CoS
to DSCP for VoIP. This mapping is accomplished by overriding the default
mapping of CoS 5 “voice bearer traffic” to DSCP 40, with DSCP 46, which is
the EF per-hop behavior for voice.
Two separate egress QoS policies are configured for the Catalyst 6500 to
accommodate the 10-Gigabit Ethernet cards which use a 1P7Q4T queuing
architecture, and the Gigabit Ethernet cards which use a 1P3Q8T queuing
architecture.
! Enable port-based QoS
auto qos default
! Class maps for 1P7Q4T 10Gb ports service policy
class-map type lan-queuing match-any PRIORITY-QUEUE
match dscp ef
match dscp cs5
match dscp cs4
match cos 5
class-map type lan-queuing match-any CONTROL-MGMT-QUEUE
match dscp cs7
match dscp cs6
match dscp cs3
match dscp cs2
match cos 3 6 7
Distribution Layer
38
class-map type lan-queuing match-any MULTIMEDIA-CONFERENCINGQUEUE
match dscp af41 af42 af43
match cos 4
class-map type lan-queuing match-any MULTIMEDIA-STREAMINGQUEUE
match dscp af31 af32 af33
class-map type lan-queuing match-any TRANSACTIONAL-DATA-QUEUE
match dscp af21 af22 af23
match cos 2
class-map type lan-queuing match-any BULK-DATA-QUEUE
match dscp af11 af12 af13
class-map type lan-queuing match-any SCAVENGER-QUEUE
match dscp cs1
match cos 1
!
policy-map type lan-queuing 1P7Q4T
class PRIORITY-QUEUE
priority
class CONTROL-MGMT-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 16 percent 60 70
random-detect dscp-based
random-detect dscp 24 percent 70 80
random-detect dscp-based
random-detect dscp 48 percent 80 90
random-detect dscp-based
random-detect dscp 56 percent 90 100
class MULTIMEDIA-CONFERENCING-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 38 percent 70 80
random-detect dscp-based
random-detect dscp 36 percent 80 90
August 2012 Series
random-detect dscp-based
random-detect dscp 34 percent 90 100
class MULTIMEDIA-STREAMING-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 30 percent 70 80
random-detect dscp-based
random-detect dscp 28 percent 80 90
random-detect dscp-based
random-detect dscp 26 percent 90 100
class TRANSACTIONAL-DATA-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 22 percent 70 80
random-detect dscp-based
random-detect dscp 20 percent 80 90
random-detect dscp-based
random-detect dscp 18 percent 90 100
class BULK-DATA-QUEUE
bandwidth remaining percent 6
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 14 percent 70 80
random-detect dscp-based
random-detect dscp 12 percent 80 90
random-detect dscp-based
random-detect dscp 10 percent 90 100
class SCAVENGER-QUEUE
bandwidth remaining percent 2
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 8 percent 80 100
class class-default
queue-buffers ratio 25
random-detect dscp-based aggregate
Distribution Layer
39
random-detect dscp values 0 1 2 3 4 5 6 7 percent 80 100
random-detect dscp values 9 11 13 15 17 19 21 23 percent 80
100
random-detect dscp values 25 27 29 31 33 35 37 39 percent 80
100
random-detect dscp values 41 42 43 44 45 47 49 50 percent 80
100
random-detect dscp values 51 52 53 54 55 57 58 59 percent 80
100
random-detect dscp values 60 61 62 63 percent 80 100
!
table-map cos-discard-class-map
map from 0 to 0
map from 1 to 8
map from 2 to 16
map from 3 to 24
map from 4 to 32
map from 5 to 46
map from 6 to 48
map from 7 to 56
!
! Class maps for 1P3Q8T 1Gb ports service policy
class-map type lan-queuing match-any PRIORITY-QUEUE-GIG
match cos 5 4
class-map type lan-queuing match-any CONTROL-AND-STREAM-MEDIA
match cos 7 6 3 2
class-map type lan-queuing match-any BULK-DATA-SCAVENGER
match cos 1
!
policy-map type lan-queuing 1P3Q8T
class PRIORITY-QUEUE-GIG
priority
queue-buffers ratio 15
class CONTROL-AND-STREAM-MEDIA
bandwidth remaining percent 55
queue-buffers ratio 40
random-detect cos-based
August 2012 Series
random-detect cos 2 percent 60 70
random-detect cos-based
random-detect cos 3 percent 70 80
random-detect cos-based
random-detect cos 6 percent 80 90
random-detect cos-based
random-detect cos 7 percent 90 100
class BULK-DATA-SCAVENGER
bandwidth remaining percent 10
queue-buffers ratio 20
random-detect cos-based
random-detect cos 1 percent 80 100
class class-default
queue-buffers ratio 25
random-detect cos-based
random-detect cos 0 percent 80 100
!
!
macro name EgressQoSTenGig
service-policy type lan-queuing output 1P7Q4T
@
!
macro name EgressQoS
service-policy type lan-queuing output 1P3Q8T
@
Option 2. Configure the Catalyst 4507R+E platform
Step 1: To make consistent deployment of QoS easier, each platform
defines two macros that you use in later procedures to apply the platformspecific QoS configuration.
class-map match-all VOIP_DATA_CLASS
match cos 5
class-map match-all VOIP_SIGNAL_CLASS
match cos 3
!
policy-map CISCOPHONE-POLICY
class VOIP_DATA_CLASS
Distribution Layer
40
set dscp ef
police 128k bc 8000
conform-action transmit
exceed-action drop
class VOIP_SIGNAL_CLASS
set dscp cs3
police 32k bc 8000
conform-action transmit
exceed-action drop
class class-default
set dscp default
police 10m bc 8000
conform-action transmit
exceed-action set-dscp-transmit cs1
!
class-map match-any PRIORITY-QUEUE
match dscp ef
match dscp cs5
match dscp cs4
class-map match-any CONTROL-MGMT-QUEUE
match dscp cs7
match dscp cs6
match dscp cs3
match dscp cs2
class-map match-any MULTIMEDIA-CONFERENCING-QUEUE
match dscp af41 af42 af43
class-map match-any MULTIMEDIA-STREAMING-QUEUE
match dscp af31 af32 af33
class-map match-any TRANSACTIONAL-DATA-QUEUE
match dscp af21 af22 af23
class-map match-any BULK-DATA-QUEUE
match dscp af11 af12 af13
class-map match-any SCAVENGER-QUEUE
match dscp cs1
!
policy-map 1P7Q1T
class PRIORITY-QUEUE
August 2012 Series
priority
class CONTROL-MGMT-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-CONFERENCING-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-STREAMING-QUEUE
bandwidth remaining percent 10
class TRANSACTIONAL-DATA-QUEUE
bandwidth remaining percent 10
dbl
class BULK-DATA-QUEUE
bandwidth remaining percent 4
dbl
class SCAVENGER-QUEUE
bandwidth remaining percent 1
class class-default
bandwidth remaining percent 25
dbl
!
policy-map 1P7Q1T_Access
class PRIORITY-QUEUE
priority
police cir percent 30
class CONTROL-MGMT-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-CONFERENCING-QUEUE
bandwidth remaining percent 10
class MULTIMEDIA-STREAMING-QUEUE
bandwidth remaining percent 10
class TRANSACTIONAL-DATA-QUEUE
bandwidth remaining percent 10
dbl
class BULK-DATA-QUEUE
bandwidth remaining percent 4
dbl
class SCAVENGER-QUEUE
bandwidth remaining percent 1
Distribution Layer
41
class class-default
bandwidth remaining percent 25
dbl
!
macro name AccessEdgeQoS
qos trust device cisco-phone
service-policy input CISCOPHONE-POLICY
service-policy output 1P7Q1T_Access
@
!
macro name EgressQoS
service-policy output 1P7Q1T
@
Step 2: When you configure a Catalyst 4507R+E with two Supervisor Engine
7-Es, configure the switch to use Stateful Switchover (SSO) when moving the
primary supervisor functionality between modules. To enable a fast transparent data plane failover, SSO synchronizes active process information as
well as configuration information between supervisor modules.
redundancy
mode sso
To enable SSO mode you must have a license level of ipbase or entservices
operating on the switch supervisors. You can check the current license level
of operation with a show version command.
Option 3. Configure the Catalyst 3750-X platform
Step 1: When there are multiple switches configured in a stack, one of the
switches controls the operation of the stack. This switch is called the stack
master.
When three or more switches are configured as a stack, configure the
stack master switch functionality on a switch that does not have uplinks
configured.
switch [switch number] priority 15
If you configure stack master switch priority on Cisco 3750-X switch stack, a
single reboot is required to force the stack master to operate on the switch
that you configured with the highest priority. Reboot the switch stack after all
of your configuration is complete for this entire “Configuring the Distribution
Layer” process.
August 2012 Series
Step 2: By default, the newly active stack master switch assigns a new stack
MAC address when the stack master switch fails. This new MAC address
assignment can cause the network to reconverge because LACP and many
other protocols rely on the stack MAC address and must restart. As such,
you should use the stack-mac persistent timer 0 command to ensure that
the original master MAC address remains the stack MAC address after a
failure.
stack-mac persistent timer 0
Step 3: To make consistent deployment of QoS easier, each platform
defines two macros that will be used in later procedures to apply the platform specific QoS configuration. Since AutoQoS might not be configured
on this device, manually configure the global QoS settings by running the
following commands:
mls qos map policed-dscp 0 10 18 to 8
mls qos map cos-dscp 0 8 16 24 32 46 48 56
mls qos srr-queue input bandwidth 70 30
mls qos srr-queue input threshold 1 80 90
mls qos srr-queue input priority-queue 2 bandwidth 30
mls qos srr-queue input cos-map queue 1 threshold 2 3
mls qos srr-queue input cos-map queue 1 threshold 3 6 7
mls qos srr-queue input cos-map queue 2 threshold 1 4
mls qos srr-queue input dscp-map queue 1 threshold 2 24
mls qos srr-queue input dscp-map queue 1 threshold 3 48 49 50
51 52 53 54 55
mls qos srr-queue input dscp-map queue 1 threshold 3 56 57 58
59 60 61 62 63
mls qos srr-queue input dscp-map queue 2 threshold 3 32 33 40
41 42 43 44 45
mls qos srr-queue input dscp-map queue 2 threshold 3 46 47
mls qos srr-queue output cos-map queue 1 threshold 3 4 5
mls qos srr-queue output cos-map queue 2 threshold 1 2
mls qos srr-queue output cos-map queue 2 threshold 2 3
mls qos srr-queue output cos-map queue 2 threshold 3 6 7
mls qos srr-queue output cos-map queue 3 threshold 3 0
mls qos srr-queue output cos-map queue 4 threshold 3 1
mls qos srr-queue output dscp-map queue 1 threshold 3 32 33 40
41 42 43 44 45
mls qos srr-queue output dscp-map queue 1 threshold 3 46 47
Distribution Layer
42
mls qos srr-queue output dscp-map queue 2 threshold 1 16 17 18
19 20 21 22 23
mls qos srr-queue output dscp-map queue 2 threshold 1 26 27 28
29 30 31 34 35
mls qos srr-queue output dscp-map queue 2 threshold 1 36 37 38
39
mls qos srr-queue output dscp-map queue 2 threshold 2 24
mls qos srr-queue output dscp-map queue 2 threshold 3 48 49 50
51 52 53 54 55
mls qos srr-queue output dscp-map queue 2 threshold 3 56 57 58
59 60 61 62 63
mls qos srr-queue output dscp-map queue 3 threshold 3 0 1 2 3
4 5 6 7
mls qos srr-queue output dscp-map queue 4 threshold 1 8 9 11
13 15
mls qos srr-queue output dscp-map queue 4 threshold 2 10 12 14
mls qos queue-set output 1 threshold 1 100 100 50 200
mls qos queue-set output 1 threshold 2 125 125 100 400
mls qos queue-set output 1 threshold 3 100 100 100 3200
mls qos queue-set output 1 threshold 4 60 150 50 200
mls qos queue-set output 1 buffers 15 25 40 20
mls qos
!
macro name EgressQoS
mls qos trust dscp
queue-set 1
srr-queue bandwidth share 1 30 35 5
priority-queue out
@
!
Procedure 2
Configure LAN switch universal settings
In this design, there are features and services that are common across all LAN
switches, regardless of the type of platform or role in the network. These are
system settings that simplify and secure the management of the solution.
August 2012 Series
This procedure provides examples for some of those settings. The actual
settings and values will depend on your current network configuration.
Table 3 - Common network services used in the deployment examples
Service
Address
Domain Name:
cisco.local
Active Directory, DNS, DHCP Server:
10.4.48.10
Authentication Control System:
10.4.48.15
Network Time Protocol Server:
10.4.48.17
EIGRP AS
100
Multicast Range
239.1.0.0/16
Step 1: Configure the device hostname to make it easy to identify the
device.
hostname [hostname]
Step 2: Configure VTP transparent mode. This deployment uses VTP
transparent mode because the benefits of dynamic propagation of VLAN
information across the network are not worth the potential for unexpected
behavior that is due to operational error.
VLAN Trunking Protocol (VTP) allows network managers to configure a
VLAN in one location of the network and have that configuration dynamically
propagate out to other network devices. However, in most cases, VLANs are
defined once during switch setup with few, if any, additional modifications.
vtp mode transparent
Step 3: Enable Rapid Per-VLAN Spanning-Tree (PVST+). Rapid PVST+
provides an instance of RSTP (802.1w) per VLAN. Rapid PVST+ greatly
improves the detection of indirect failures or linkup restoration events over
classic spanning tree (802.1D).
Although this architecture is built without any Layer 2 loops, you must still
enable spanning tree. By enabling spanning tree, you ensure that if any
physical or logical loops are accidentally configured, no actual layer 2 loops
occur.
spanning-tree mode rapid-pvst
Distribution Layer
43
Step 4: Set the distribution layer switch to be the spanning-tree root for all
VLANs on access layer switches or appliances that you are connecting to
the distribution switch.
spanning-tree vlan 1-4094 root primary
Step 5: Enable Unidirectional Link Detection (UDLD).
UDLD is a Layer 2 protocol that enables devices connected through fiberoptic or twisted-pair Ethernet cables to monitor the physical configuration
of the cables and detect when a unidirectional link exists. When UDLD
detects a unidirectional link, it disables the affected interface and alerts you.
Unidirectional links can cause a variety of problems, including spanning-tree
loops, black holes, and non-deterministic forwarding. In addition, UDLD
enables faster link failure detection and quick reconvergence of interface
trunks, especially with fiber, which can be susceptible to unidirectional
failures.
udld enable
Step 6: Set EtherChannels to use the traffic source and destination IP
address when calculating which link to send the traffic across. This normalizes the method in which traffic is load-shared across the member links
of the EtherChannel. EtherChannels are used extensively in this design
because of their resiliency capabilities.
port-channel load-balance src-dst-ip
Step 7: Configure DNS for host lookup.
At the command line of a Cisco IOS device, it is helpful to be able to type a
domain name instead of the IP address for a destination.
ip name-server 10.4.48.10
Step 8: Configure device management protocols.
Secure HTTP (HTTPS) and Secure Shell (SSH) are more secure replacements for the HTTP and Telnet protocols. They use Secure Sockets Layer
(SSL) and Transport Layer Security (TLS) to provide device authentication
and data encryption.
The SSH and HTTPS protocols enable secure management of the LAN
device. Both protocols are encrypted for privacy, and the nonsecure protocols, Telnet and HTTP, are turned off.
August 2012 Series
Specify the transport preferred none on vty lines to prevent errant connection attempts from the CLI prompt. Without this command, if the ip
name server is unreachable, long timeout delays may occur for mistyped
commands.
ip domain-name cisco.local
ip ssh version 2
no ip http server
ip http secure-server
!
line vty 0 15
transport input ssh
transport preferred none
Step 9: Enable Simple Network Management Protocol (SNMP) in order
to allow the network infrastructure devices to be managed by a Network
Management System (NMS), and then configure SNMPv2c both for a readonly and a read-write community string.
snmp-server community cisco RO
snmp-server community cisco123 RW
Step 10: If your network operational support is centralized, you can
increase network security by using an access list to limit the networks that
can access your device. In this example, only devices on the 10.4.48.0/24
network will be able to access the device via SSH or SNMP.
access-list 55 permit 10.4.48.0 0.0.0.255
line vty 0 15
access-class 55 in
!
snmp-server community cisco RO 55
snmp-server community cisco123 RW 55
Caution
If you configure an access-list on the vty interface you may lose
the ability to use ssh to login from one router to the next for hopby-hop troubleshooting.
Distribution Layer
44
Step 11: Configure local login and password
The local login account and password provides basic device access authentication to view platform operation. The enable password secures access
to the device configuration mode. By enabling password encryption, you
prevent the use of plain text passwords when viewing configuration files.
username admin password c1sco123
enable secret c1sco123
service password-encryption
aaa new-model
By default, https access to the switch will use the enable password for
authentication.
Step 12: If you want to reduce operational tasks per device, configure
centralized user authentication by using the TACACS+ protocol to authenticate management logins on the infrastructure devices to the Authentication,
Authorization and Accounting (AAA) server.
As networks scale in the number of devices to maintain, there is an operational burden to maintain local user accounts on every device. A centralized
Authentication, Authorization and Accounting (AAA) service reduces operational tasks per device and provides an audit log of user access for security
compliance and root cause analysis. When AAA is enabled for access
control, all management access to the network infrastructure devices (SSH
and HTTPS) is controlled by AAA.
TACACS+ is the primary protocol used to authenticate management
logins on the infrastructure devices to the AAA server. A local AAA user
database is also defined on each network infrastructure device to provide
a fallback authentication source in case the centralized TACACS+ server is
unavailable.
tacacs server TACACS-SERVER-1
address ipv4 10.4.48.15
key SecretKey
!
aaa group server tacacs+ TACACS-SERVERS
server name TACACS-SERVER-1
!
aaa authentication login default group TACACS-SERVERS local
aaa authorization exec default group TACACS-SERVERS local
aaa authorization console
ip http authentication aaa
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For Catalyst 6500 use the following set of commands to enable the same
AAA functionality.
aaa authentication login default group tacacs+ local
aaa authorization exec default group tacacs+ local
aaa authorization console
ip http authentication aaa
tacacs-server host 10.4.48.15 key SecretKey
Reader Tip
The AAA server used in this architecture is Cisco Authentication
Control System. Configuration of ACS is discussed in the Device
Management Using ACS Deployment Guide.
Step 13: Configure a synchronized clock by programming network devices
to synchronize to a local NTP server in the network. The local NTP server
typically references a more accurate clock feed from an outside source.
Configure console messages, logs, and debug output to provide time
stamps on output, which allows cross-referencing of events in a network.
ntp server 10.4.48.17
ntp update-calendar
!
clock timezone PST -8
clock summer-time PDT recurring
!
service timestamps debug datetime msec localtime
service timestamps log datetime msec localtime
The ntp update-calendar command configures the switch to update the
hardware clock from the ntp time source periodically. Since not all switches
have a hardware clock, this command is not supported by all devices.
Distribution Layer
45
Procedure 3
Configure distribution global settings
Step 1: Configure BPDU Guard globally to protect portfast enabled
interfaces.
In some scenarios a service appliance that requires spanning-tree portfast
may be connected to the distribution layer. When an interface is set for
portfast, BPDU guard protects against an accidental connection of another
switch into a portfast enabled interface, which could cause a catastrophic
undetected spanning-tree loop.
If a portfast configured interface receives a BPDU, an invalid configuration
exists, such as the connection of an unauthorized device. The BPDU guard
feature prevents loops by moving a nontrunking interface into an errdisable
state when a BPDU is received on an interface when portfast is enabled.
Disable the interface if another switch is plugged into the portfast enabled
interface.
spanning-tree portfast bpduguard default
On the Catalyst 6500 the global BPDU Guard command is slightly different.
spanning-tree portfast edge bpduguard default
Step 2: Configure an in-band management interface.
The loopback interface is a logical interface that is always reachable as long
as the device is powered on and any IP interface is reachable to the network.
Because of this capability, the loopback address is the best way to manage
the switch in-band. Layer 3 process and features are also bound to the
loopback interface to ensure process resiliency.
The loopback address is commonly a host address with a 32-bit address
mask. Allocate the loopback address from the IP address block that the
distribution switch summarizes to the rest of the network.
interface Loopback0
ip address [ip address] 255.255.255.255
ip pim sparse-mode
The need for the ip pim sparse-mode command will be explained further in
Step 3 of Procedure 5 “Configure IP Multicast routing”.
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Step 3: Configure the SNMP and SSH processes to use the loopback
interface address for optimal resiliency:
snmp-server trap-source Loopback 0
ip ssh source-interface Loopback 0
ip pim register-source Loopback 0
ip tacacs source-interface Loopback 0
ntp source Loopback 0
Procedure 4
Configure IP unicast routing
Enhanced IGRP (EIGRP) is the IP unicast routing protocol used in this design
because it is easy to configure, does not require a large amount of planning,
has flexible summarization and filtering, and can scale to large networks.
The single logical distribution layer design uses stateful switchover and nonstop forwarding to provide subsecond failover in the event of a supervisor
data or control plane failure. This ability reduces packet loss in switchover to
redundant logic and keeps packets flowing when the data plane is still intact
to adjacent nodes. In the stack-based distribution layer approach, a single
logical control point still exists and the master control plane in a stack can
fail over to another member in the stack providing near-second or subsecond resiliency.
When the supervisor or master switch of a distribution platform switches
over from the active to the hot-standby supervisor, it will continue switching
IP data traffic flows in hardware. However, the supervisor requires time to
reestablish control plane two-way peering with EIGRP routing neighbors and
avoid the peer router from tearing down adjacencies due to missed hellos
that would cause a reroute and disruption of traffic. To allow this time for the
supervisor to recover, there is a Nonstop Forwarding (NSF) setting for the
routing protocol to wait for the dual supervisor peer switch to recover. The
neighboring router is said to be NSF-aware if it has a newer release of IOS
that recognizes an NSF peer. All of the platforms used in this design are
NSF-aware for the routing protocols in use.
The distribution layer switch must be configured to enable NSF for the protocol in use so that it can signal a peer when it switches over to a hot-standby
supervisor for the peering neighbor to allow it time to reestablish the EIGRP
protocol to that node. No tuning of the default NSF timers is needed in this
network. Nothing has to be configured for an NSF-aware peer router.
Distribution Layer
46
Step 1: Enable EIGRP for the IP address space that the network will be
using. If needed for your network, you can enter multiple network statements. Disable auto summarization of the IP networks and enable all routed
links to be passive by default. The Loopback 0 IP address is used for the
EIGRP router ID to ensure maximum resiliency.
ip routing
!
router eigrp 100
network 10.4.0.0 0.1.255.255
no auto-summary
passive-interface default
eigrp router-id [ip address of loopback 0]
nsf
The RP is a control plane operation that should be placed in the core of the
network or close to the IP Multicast sources on a pair of Layer 3 switches
or routers. IP Multicast routing begins at the distribution layer if the access
layer is Layer 2 and provides connectivity to the IP Multicast RP. In designs
without a core layer, the distribution layer will perform the RP function.
Figure 27 - Rendezvous point placement in the network
Rendezvous Point
WAN
Multicast Source
in the Data Center
2109
Cisco Catalyst 6500 does not require the ip routing command because it is
enabled by default on that platform.
Tech Tip
Verify that eigrp stub connected summary is not configured
in your EIGRP routing instance. This command may have been
automatically configured if you have changed platform licensing
from an ip base capable image.
In this design, which is based on sparse mode multicast operation, Cisco
uses Anycast RP to provide a simple yet scalable way to provide a highly
resilient RP environment.
Step 1: Configure IP Multicast routing on the platforms in the global configuration mode.
ip multicast-routing
Procedure 5
Configure IP Multicast routing
IP Multicast allows a single IP data stream to be replicated by the infrastructure (that is, routers and switches) and sent from a single source to multiple
receivers. Using IP Multicast is much more efficient than multiple individual
unicast streams or a broadcast stream that would propagate everywhere.
IP Telephony Music on Hold and IP Video Broadcast Streaming are two
examples of IP Multicast applications.
To receive a particular IP Multicast data stream, end hosts must join a multicast
group by sending an Internet Group Management Protocol (IGMP) message to
their local multicast router. In a traditional IP Multicast design, the local router
consults another router in the network that is acting as a Rendezvous Point
(RP) to map the receivers to active sources so they can join their streams.
August 2012 Series
Cisco Catalyst 3750 Series switches instead require the ip multicastrouting distributed command.
Step 2: Configure the switch to discover the IP Multicast RP.
Every Layer 3 switch and router must be configured to discover the IP
Multicast RP with autorp. Use the ip pim autorp listener command to allow
for discovery across sparse mode links. This configuration provides for
future scaling and control of the IP Multicast environment and can change
based on network needs and design.
ip pim autorp listener
Step 3: Configure ip pim sparse-mode. All Layer 3 interfaces in the network
must be enabled for sparse mode multicast operation.
ip pim sparse-mode
Distribution Layer
47
Example
Step 1: Configure loopback interface for RP.
spanning-tree portfast bpduguard default
!
interface Loopback 0
ip address 10.4.15.254 255.255.255.255
ip pim sparse-mode
!
snmp-server trap-source Loopback 0
ip ssh source-interface Loopback 0
ip pim register-source Loopback 0
ip tacacs source-interface Loopback 0
ntp source Loopback 0
!
ip routing
!
router eigrp 100
network 10.4.0.0 0.1.255.255
no auto-summary
passive-interface default
eigrp router-id 10.4.15.254
nsf
!
ip multicast-routing
ip pim autorp listener
!
Procedure 6
Configure IP Multicast RP
(Optional)
In networks without a core layer, the RP function can be placed on the
distribution layer. If a core layer does exist follow the IP Multicast Procedure
4 in the core layer section to configure the RP function.
Every Layer 3 switch and router must know the address of the IP Multicast
RP, including the core switches that are serving as the RP. This design uses
AutoRP to announce candidate RPs, which are the core switches, to the rest
of the network.
August 2012 Series
Configure a second loopback interface to be used as the RP interface. The
interface uses a host address mask (32 bits). All routers then point to this
common IP address on loopback 1 for the RP.
interface Loopback 1
ip address 10.4.15.253 255.255.255.255
ip pim sparse-mode
Step 2: Configure AutoRP candidate RP.
The send-rp-announce command in conjunction with the group-list option
advertises the RP address, with the multicast range the device is willing to
serve, as a candidate RP to the AutoRP mapping agents.
access-list 10 permit 239.1.0.0 0.0.255.255
ip pim send-rp-announce Loopback 1 scope 32 group-list 10
Step 3: Configure AutoRP mapping agent.
The AutoRP mapping agent listens for candidate RPs and then advertises
to the rest of the network the list of available RPs. The send-rp-discovery
command enables this switch to act as an AutoRP mapping agent.
ip pim send-rp-discovery Loopback0 scope 32
In the event you add a core layer to your existing network and the RP is
currently configured on a distribution layer, you may want to move the RP
to the core. You can do this by following the IP Multicast section in the core
layer IP Multicast procedure and program the RP address on the loopback 1
interfaces at the new location with the same ip address used on loopback 1
in this procedure, then enable and establish IP Multicast and MSDP peering.
All remote routers should still point to the same RP address, which simplifies
the move and reduces disruption to the IP Multicast environment.
Procedure 7
Connect to access layer
The resilient, single, logical, distribution layer switch design is based on a
hub-and-spoke or star design. The links to access layer switches and connected routers are Layer 2 EtherChannels. Links to other distribution layers,
and the optional core are Layer 3 links or Layer 3 EtherChannels.
When using EtherChannel, the member interfaces should be on different
switches in the stack or different modules in the modular switch for the
highest resiliency.
Distribution Layer
48
The physical interfaces that are members of a Layer 2 EtherChannel are
configured prior to configuring the logical port-channel Interface. This
allows for minimal configuration because most of the commands entered to
a port-channel interface are copied to its members’ interfaces and do not
require manual replication.
Configure two or more physical interfaces to be members of the
EtherChannel. It is recommended that they are added in multiples of two.
If this distribution layer will be used as a network-services aggregation
block, you likely will not have an access layer to connect.
Step 1: Configure VLANs.
Configure all VLANs for the access layer switches that you are connecting to
the distribution switch.
vlan
name
vlan
name
vlan
name
[data vlan]
Data
[voice vlan]
Voice
[management vlan]
Management
Step 2: If there is no external central site DHCP server in the network, you
can provide DHCP service in IOS by configuring the IOS DHCP server. This
function can also be useful at a remote-site where you want to provide local
DHCP service and not depend on the WAN link to an external central site
DHCP server.
ip dhcp excluded-address 10.4.100.1 10.4.100.10
ip dhcp pool access
network 10.4.100.0 255.255.255.0
default-router 10.4.100.1
domain-name cisco.local
dns-server 10.4.48.10
The example configuration provides IP addresses via the IOS based DHCP
service for the subnet 10.4.100.0/24 and prevents the server from assigning
reserved addresses .1-.10.
Step 3: Configure EtherChannel member interfaces.
Cisco uses Layer 2 EtherChannels to connect all access layer switches to
the distribution layer and thereby create the hub-and-spoke resilient design
that eliminates spanning-tree loops.
August 2012 Series
Connect the access layer EtherChannel uplinks to separate switches in
the distribution layer switches or stack, and in the case of Cisco Catalyst
4507R+E distribution layer, to separate redundant modules for additional
resiliency.
Also, apply the egress QoS macro that was defined in the platform configuration procedure to ensure traffic is prioritized appropriately.
interface [interface type] [port 1]
description Link to {your device here} port 1
interface [interface type] [port 2]
description Link to {your device here} port 2
!
interface range [interface type] [port 1], [interface type]
[port 2]
switchport
macro apply EgressQoS
channel-protocol lacp
channel-group [number] mode active
logging event link-status
logging event trunk-status
logging event bundle-status
Tech Tip
The Catalyst 6500 has two egress QoS macros, EgressQoS which
is used for Gigabit Ethernet ports, and EgressQoSTenGig which is
used for Ten Gigabit Ethernet ports. All other Cisco SBA distribution layer platforms have a single egress QoS macro that applies
to Gigabit and Ten Gigabit Ethernet ports.
Step 4: Configure a trunk.
An 802.1Q trunk is used for the connection to the access layer, which allows
the distribution switch to provide Layer 3 services to all the VLANs defined
on the access layer switch. Prune the VLANs on the trunk to only the VLANs
that are active on the access switch. When using EtherChannel the interface
type will be port-channel and the number must match the channel group
configured in Step 3 .
Distribution Layer
49
interface [port-channel] [number]
description EtherChannel link to {your device here}
switchport trunk allowed vlan [data vlan],[voice vlan],
[mgmt vlan]
switchport mode trunk
logging event link-status
no shutdown
If the interface type is not portchannel, then the additional command macro
apply EgressQoS must also be configured on the interface.
Next, mitigate VLAN hopping on the trunk for switch-to-switch connections.
There is a remote possibility that an attacker can create a double 802.1Q
encapsulated packet. If the attacker has specific knowledge of the 802.1Q
native VLAN, they could create a packet that when processed, removes the
first or outermost tag when the packet is switched onto the untagged native
VLAN. When the packet reaches the target switch, the inner or second tag
is then processed and the potentially malicious packet is switched to the
target VLAN.
At first glance, this appears to be a serious risk. However, the traffic in this
attack scenario is in a single direction and no return traffic can be switched
by this mechanism. Additionally, this attack cannot work unless the attacker
knows the native VLAN ID.
Step 5: To remove the remote risk of this type of attack is to configure an
unused VLAN on all switch-to-switch 802.1Q trunk links from access layer
to distribution layer. By using a hard to guess, unused VLAN for the native
VLAN you reduce the possibility that a double 802.1Q-tagged packet can
hop VLANs.
vlan 999
!
interface [port-channel] [number]
switchport trunk native vlan 999
Step 6: Configure Layer 3.
Configure a VLAN interface (SVI) for every access layer VLAN so devices in
the VLAN can communicate with the rest of the network.
Use the ip helper-address command to allow remote DHCP servers to provide IP addresses for this network. The address that the helper command
August 2012 Series
points to is the central DHCP server. If you have more than one DHCP server,
you can list multiple helper commands on an interface.
interface vlan [number]
ip address [ip address] [mask]
ip helper-address [dhcp server ip]
ip pim sparse-mode
no shutdown
If you configured the IOS DHCP server function on this distribution layer
switch in Step 2 of this procedure, the ip helper-address is not needed on
the VLAN interface.
Example
802.1Q Trunk
VLANs 100,101,115
Native VLAN 999
VLAN 100
Data VLAN
VLAN 101
Voice VLAN
VLAN 115
Management
VLAN
LAN
Distribution
Switch
2099
The Catalyst 3750 requires the switchport trunk encapsulation dot1q
command.
vlan 100
name Data
vlan 101
name Voice
vlan 115
name Management
spanning-tree vlan 1-4094 root primary
!
interface GigabitEthernet 1/1/1
description Link to Access Switch port 1
interface GigabitEthernet 2/1/1
description Link to Access Switch port 2
!
interface range GigabitEthernet 1/1/1, GigabitEthernet 2/1/1
switchport
macro apply EgressQoS
channel-protocol lacp
Distribution Layer
50
channel-group
logging event
logging event
logging event
no shutdown
10 mode active
link-status
trunk-status
bundle-status
!
interface Port-channel 10
description EtherChannel link to Access Switch
switchport trunk native vlan 999
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 100,101,115
switchport mode trunk
no shutdown
!
interface vlan 100
ip address 10.4.0.1 255.255.255.0
ip helper-address 10.4.48.10
ip pim sparse-mode
!
interface vlan 101
ip address 10.4.1.1 255.255.255.0
ip helper-address 10.4.48.10
ip pim sparse-mode
!
interface vlan 115
ip address 10.4.15.1 255.255.255.128
ip helper-address 10.4.48.10
ip pim sparse-mode
Procedure 8
Connect to LAN core or WAN router
Any links to connected WAN routers or a LAN core layer should be Layer 3
links or Layer 3 EtherChannels. The SBA LAN design does not extend Layer
2 VLANs beyond the distribution layer.
Option 1. Connect distribution layer switch to WAN router
When the LAN distribution layer connects to a WAN router this may present
a number of scenarios:
• The distribution layer switch is a collapsed core HQ location connecting
to one or more WAN headend routers.
• The distribution layer switch is collapsed core for a larger remote site
with multiple WAN routers for survivability.
• The distribution layer switch is a WAN aggregation switch with a number
of WAN headend routers connected to it for a modular block connecting
to a LAN Core switch.
Because of the number of combinations, it is better to consult the Cisco
SBA—Borderless Networks WAN deployment guides for the LAN connectivity that matches your deployment scenario.
Option 2. Connect distribution layer switch to LAN core
switch
Step 1: Configure the Layer 3 interface.
If you are using an EtherChannel to connect to the LAN core, the interface
type will be port-channel and the number must match the channelgroup number you will configure in Step 3. When configuring a Layer 3
EtherChannel the logical port-channel interface is configured prior to
configuring the physical interfaces associated with the EtherChannel.
interface [interface type] [number]
description Link to {your device here}
no switchport
ip address [ip address] [mask]
ip pim sparse-mode
logging event link-status
carrier-delay msec 0
no shutdown
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Distribution Layer
51
If the interface type is not a port-channel, then an additional command
macro apply EgressQoS must also be configured on the interface.
Tech Tip
Step 2: Configure IP address summarization on the links to the core.
As networks grow, the number of IP subnets or routes in the routing tables
grows as well. To reduce the amount of bandwidth, processor speed, and
memory necessary to carry large route tables and to reduce convergence
time around a link failure, configure IP summarization on links where logical
boundaries exist. If the connected device provides connectivity to another
piece of the network (for example, the WAN, Internet, or LAN core), configure
EIGRP summarization.
ip summary-address eigrp 100 [network] [mask]
Step 3: If you want to run EtherChannel links to the core layer, now configure EtherChannel member interfaces.
Configure the physical interfaces to tie to the logical port-channel using the
channel-group command. The number for the port-channel and channelgroup must match.
Also, apply the egress QoS macro that was defined in the platform configuration procedure to ensure that traffic is prioritized appropriately.
interface [interface type] [port 1]
description Link to {your device here} port 1
interface [interface type] [port 2]
description Link to {your device here} port 2
!
interface range [interface type] [port 1], [interface type]
[port 2]
no switchport
macro apply EgressQoS
carrier-delay msec 0
channel-protocol lacp
channel-group [number] mode active
logging event link-status
logging event trunk-status
logging event bundle-status
no shutdown
August 2012 Series
The Catalyst 6500 has two egress QoS macros, EgressQoS which
is used for Gigabit Ethernet ports, and EgressQoSTenGig which is
used for Ten Gigabit Ethernet ports. All other Cisco SBA distribution layer platforms have a single egress QoS macro that applies
to Gigabit and Ten Gigabit Ethernet ports.
Step 4: Configure the EIGRP interface.
After you have configured the Layer 3 interfaces and Layer 3 port-channels
connecting to other Layer 3 devices, allow EIGRP to form neighbor relationships across these interfaces to establish peering adjacencies and
exchange route tables.
router eigrp 100
no passive-interface [interface type] [number]
Step 5: Save the running configuration that you have entered so it will
be used as the startup configuration file when your switch is rebooted or
power-cycled.
copy running-config startup-config
Distribution Layer
52
Example
Ten 2/4/5
2110
Ten 1/4/5
PortChannel 20
10.4.40.18/30
interface Port-channel 20
description EtherChannel link to Core Switch
no switchport
ip address 10.4.40.18 255.255.255.252
ip pim sparse-mode
ip summary-address eigrp 100 10.4.0.0 255.255.240.0
no shutdown
!
interface range TenGigabitEthernet 1/4/5, TenGigabitEthernet
2/4/5
description EtherChannel link to Core Switch
no switchport
macro apply EgressQoSTenGig
carrier-delay msec 0
channel-group 20 mode on
logging event link-status
logging event trunk-status
logging event bundle-status
no shutdown
!
router eigrp 100
no passive-interface Port-channel 20
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Distribution Layer
53
Core Layer
Business Overview
Technology Overview
Modern organizations require non-stop connectivity and uninterrupted
access to the resources essential for conducting business. The risk of a
single link outage or device failure cascading throughout the facility and
disrupting communications for a large number of users increases as networks grow in size and scale at a given location. IT departments tasked with
providing reliable access to resources require a network architecture that
can provide a highly available service.
The core layer of the LAN is a critical part of the scalable network, yet
by design, is one of the simplest. Like the distribution layer aggregates
connectivity for multiple access layer switches, the core layer aggregates
connectivity when there are multiple distribution blocks. As networks grow
beyond three distribution blocks in a single location, a core layer should be
used to optimize the design.
As the LAN environment at a larger facility grows it often creates the need to
use multiple LAN distribution layer blocks. The physical layout of the site or
the density of access layer switches connecting to a single distribution layer
may necessitate the creation of multiple distribution layer blocks. As the
number of required distribution layer blocks in a facility grows beyond two
or three, a solution is required to reduce the need and cost of fully meshing all interconnectivity while maintaining a design that provides a reliable
infrastructure.
Beyond the simple aggregation of connectivity, the core layer serves to
reduce the number of paths between distribution layers, which in turn lowers
the time required to converge the network after a failure. By upgrading
bandwidth between a distribution layer and the core, multiple distribution
layer blocks can benefit from the increase versus the need to upgrade the
bandwidth to every other device in a design without a core. The core layer
is especially relevant to designs where the data center resources might be
collocated with the LAN.
An important consideration when investing in new technology and services
that drive business productivity is the time required to implement the
technology in a usable fashion. Organizations must design an architecture
of compute, storage, application, and network foundation that allows them to
reduce the time required to use new technology investments by exploiting a
flexible and scalable infrastructure.
August 2012 Series
Core Layer
54
Figure 28 - Core layer overview
Core
Switches
Distribution
Switches
Building 1
August 2012 Series
Building 2
Building 3
2111
Client Access Switches
Building 4
Core Layer
55
In large modular and scalable LAN designs, a core layer is used to aggregate
multiple user connectivity distribution layer blocks and network-services distribution layer blocks. In designs with a collocated data center, the core provides high
speed fan-out connectivity to the rest of the network. The core layer also serves
as the connection between the Wide Area Network (WAN) and Internet Edge
distribution layer blocks. Because of this central point of connectivity for all data
flows, the core is part of the backbone IP routing address space and is designed
to be highly resilient to protect from component-, power-, or operational-induced
outages. The core layer should not contain highly complex or high touch services
that require constant care and tuning, to avoid downtime required by complex
configuration changes, increased software upgrades for new services, or links
that toggle up/down as part of normal operations like user endpoint connectivity.
The core layer in the SBA design is based on two physically and logically
separate switches. Connectivity to and from the core should be Layer 3 only.
No VLANs should span the core to drive increased resiliency and stability.
Since the core does not need to provide the same services or boundaries
that the distribution layer does, the two-box design does not significantly
increase the complexity of the solution. Because the Layer 3 core has no
need to provide access layer services or Layer 2 connectivity, the single
logical device approach used in the distribution layer to prevent spanning
tree and reduce IP gateway protocols is not as beneficial.
The core is built on dual switches to provide a completely separate control
plane housed on each switch, which provides redundant logic, line cards,
hardware, and power for the backbone operation. Each distribution layer
block, router, or other appliance connecting to the core should be dual
homed with an EtherChannel or link to each core switch. This dual-homed
approach provides Equal Cost Multiple Path (ECMP) load sharing of IP traffic
across links for traffic traversing the core, and fast failover based on either
EtherChannel or ECMP alternate routes without waiting for routing protocol
topology changes to propagate the network.
The core is designed to be high speed and provides for connectivity ranging from Gigabit Ethernet, Gigabit EtherChannel, 10 Gigabit Ethernet, and up
to 10 Gigabit EtherChannel. The core can provide non-blocking bandwidth
based on design and configuration. EtherChannel links homed to a switch
should be spread across line cards when possible.
The core switches can be provisioned with dual supervisors for Stateful
Switchover (SSO) operation to protect the core bandwidth in the event that
a control plane hardware or software failure occurs. The core switches are
Nonstop Forwarding (NSF) aware to provide enhanced resilience for any
dual supervisor connected devices and NSF capable if provisioned with
dual supervisors per switch.
August 2012 Series
Core Layer Platforms
Cisco Catalyst 6500 Series switch, powered by the Supervisor 2T, is the
premier LAN core platform. It delivers scalable performance, intelligence,
and a broad set of features to address the needs of the most demanding
enterprise deployments requirements for building a modular, resilient, scalable, and secure Layer 3 backbone solution.
• Uses Cisco Catalyst 6500 Supervisor Engine 2T, which increases the
per slot switching capacity to 80 Gbps, and delivers better scalability
and enhanced hardware-enabled features. The increased performance
enables the system to provide 40 Gigabit Ethernet uplinks to satisfy the
most demanding Distribution to Core Layer connectivity.
• Cisco 6500 Supervisor 2T supports the line cards enabled for Policy
Feature Card 4 (PFC4), including the WS-X6816-10G WS-X6908-10G
and WS-X6904-40G-2T, which provide enhanced QoS and security
capabilities. The WS-X6908-10G provides eight 10Gb Ethernet ports
with 1:1 oversubscription. The WS-X6904-40G-2T provides up to
four 40Gb Ethernet ports or up to sixteen 10Gb Ethernet ports using
modular adapters for 10Gb or 40Gb Ethernet applications and can be
programmed to run in 2:1 or 1:1 oversubscription mode.
• The Supervisor 2T based switch enhances support for Cisco TrustSec
(CTS) by providing MacSec encryption and role-based access control
(RBAC) lists, and delivers improved control plane policing to address
denial-of-service attacks.
• Supports high-density connectivity for Gigabit and 10 Gigabit Ethernet
connectivity using copper or fiber optic media to provide the scale and
versatility for the core of any network.
The Catalyst 6500 used in the core layer design can use the same supervisor engine, chassis, and power supplies as the Catalyst 6500 VSS 4T
systems used for the distribution layer, which helps for sparing of parts and
reduction of platforms to support.
The Cisco SBA—Borderless Networks LAN and Data Center Collapsed
Core Using Cisco Nexus 7000 Deployment Guide discusses the use of
Cisco Nexus 7000 Series Switch as the core layer platform when the LAN
and data center core functionality are combined on one set of devices.
Core Layer
56
Deployment Details
The core layer uses a dual switch design for resiliency.
Process
Configuring the Core
1. Configure the platform
2. Configure LAN switch universal settings
3. Configure the core switch global settings
4. Configure IP Multicast routing
5. Connect to distribution layer
Procedure 1
Configure the platform
On the Catalyst 6500 Supervisor 2T-based switches, QoS is enabled
by default and policies for interface queuing are defined by attached
service policies. The QoS policies are now defined using Cisco Common
Classification Policy (C3PL) which is similar to Modular QoS CLI to reduce
operational complexity.
All interface connections in the distribution and core are set to trust DSCP.
Even though this design is configured to trust DSCP markings, it is a best
practice to ensure proper mapping of class of service (CoS) to DSCP for
VoIP. This mapping is accomplished by overriding the default mapping of
CoS 5 “voice bearer traffic” to DSCP 40, with DSCP 46, which is the EF perhop behavior for voice.
Two separate egress QoS policies are configured for the Catalyst 6500 to
accommodate the 10-Gigabit Ethernet cards which use a 1P7Q4T queuing
architecture, and the Gigabit Ethernet cards which use a 1P3Q8T queuing
architecture.
August 2012 Series
! Enable port-based QoS
auto qos default
! Class maps for 1P7Q4T 10Gb ports service policy
class-map type lan-queuing match-any PRIORITY-QUEUE
match dscp ef
match dscp cs5
match dscp cs4
match cos 5
class-map type lan-queuing match-any CONTROL-MGMT-QUEUE
match dscp cs7
match dscp cs6
match dscp cs3
match dscp cs2
match cos 3 6 7
class-map type lan-queuing match-any MULTIMEDIA-CONFERENCINGQUEUE
match dscp af41 af42 af43
match cos 4
class-map type lan-queuing match-any MULTIMEDIA-STREAMINGQUEUE
match dscp af31 af32 af33
class-map type lan-queuing match-any TRANSACTIONAL-DATA-QUEUE
match dscp af21 af22 af23
match cos 2
class-map type lan-queuing match-any BULK-DATA-QUEUE
match dscp af11 af12 af13
class-map type lan-queuing match-any SCAVENGER-QUEUE
match dscp cs1
match cos 1
!
policy-map type lan-queuing 1P7Q4T
class PRIORITY-QUEUE
priority
class CONTROL-MGMT-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
Core Layer
57
random-detect dscp 16 percent 60 70
random-detect dscp-based
random-detect dscp 24 percent 70 80
random-detect dscp-based
random-detect dscp 48 percent 80 90
random-detect dscp-based
random-detect dscp 56 percent 90 100
class MULTIMEDIA-CONFERENCING-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 38 percent 70 80
random-detect dscp-based
random-detect dscp 36 percent 80 90
random-detect dscp-based
random-detect dscp 34 percent 90 100
class MULTIMEDIA-STREAMING-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 30 percent 70 80
random-detect dscp-based
random-detect dscp 28 percent 80 90
random-detect dscp-based
random-detect dscp 26 percent 90 100
class TRANSACTIONAL-DATA-QUEUE
bandwidth remaining percent 14
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 22 percent 70 80
random-detect dscp-based
random-detect dscp 20 percent 80 90
random-detect dscp-based
random-detect dscp 18 percent 90 100
class BULK-DATA-QUEUE
bandwidth remaining percent 6
queue-buffers ratio 10
August 2012 Series
random-detect dscp-based
random-detect dscp 14 percent 70 80
random-detect dscp-based
random-detect dscp 12 percent 80 90
random-detect dscp-based
random-detect dscp 10 percent 90 100
class SCAVENGER-QUEUE
bandwidth remaining percent 2
queue-buffers ratio 10
random-detect dscp-based
random-detect dscp 8 percent 80 100
class class-default
queue-buffers ratio 25
random-detect dscp-based aggregate
random-detect dscp values 0 1 2 3 4 5 6 7 percent 80 100
random-detect dscp values 9 11 13 15 17 19 21 23 percent 80
100
random-detect dscp values 25 27 29 31 33 35 37 39 percent 80
100
random-detect dscp values 41 42 43 44 45 47 49 50 percent 80
100
random-detect dscp values 51 52 53 54 55 57 58 59 percent 80
100
random-detect dscp values 60 61 62 63 percent 80 100
!
table-map cos-discard-class-map
map from 0 to 0
map from 1 to 8
map from 2 to 16
map from 3 to 24
map from 4 to 32
map from 5 to 46
map from 6 to 48
map from 7 to 56
!
! Class maps for 1P3Q8T 1Gb ports service policy
class-map type lan-queuing match-any PRIORITY-QUEUE-GIG
Core Layer
58
match cos 5 4
class-map type lan-queuing match-any CONTROL-AND-STREAM-MEDIA
match cos 7 6 3 2
class-map type lan-queuing match-any BULK-DATA-SCAVENGER
match cos 1
!
policy-map type lan-queuing 1P3Q8T
class PRIORITY-QUEUE-GIG
priority
queue-buffers ratio 15
class CONTROL-AND-STREAM-MEDIA
bandwidth remaining percent 55
queue-buffers ratio 40
random-detect cos-based
random-detect cos 2 percent 60 70
random-detect cos-based
random-detect cos 3 percent 70 80
random-detect cos-based
random-detect cos 6 percent 80 90
random-detect cos-based
random-detect cos 7 percent 90 100
class BULK-DATA-SCAVENGER
bandwidth remaining percent 10
queue-buffers ratio 20
random-detect cos-based
random-detect cos 1 percent 80 100
class class-default
queue-buffers ratio 25
random-detect cos-based
random-detect cos 0 percent 80 100
!
macro name EgressQoSTenGig
service-policy type lan-queuing output 1P7Q4T
@
!
macro name EgressQoS
service-policy type lan-queuing output 1P3Q8T
@
August 2012 Series
Procedure 2
Configure LAN switch universal settings
In this design, there are features and services that are common across all
LAN switches, regardless of the type of platform or role in the network.
These are system settings that simplify and secure the management of the
solution.
This procedure provides examples for some of these settings. The actual
settings and values depend on your current network configuration.
Table 4 - Common network services used in the deployment examples
Service
Address
Domain Name:
cisco.local
Active Directory, DNS, DHCP Server:
10.4.48.10
Authentication Control System:
10.4.48.15
Network Time Protocol Server:
10.4.48.17
EIGRP AS
100
Multicast Range
239.1.0.0/16
Step 1: Configure the device hostname to make it easy to identify the
device.
hostname [hostname]
Step 2: Configure VTP transparent mode. This deployment uses VTP
transparent mode because the benefits of dynamic propagation of VLAN
information across the network are not worth the potential for unexpected
behavior that is due to operational error.
VLAN Trunking Protocol (VTP) allows network managers to configure a
VLAN in one location of the network and have that configuration dynamically
propagate out to other network devices. However, in most cases, VLANs are
defined once during switch setup with few, if any, additional modifications.
vtp mode transparent
Step 3: Enable Rapid Per-VLAN Spanning-Tree (PVST+). Rapid PVST+
provides an instance of RSTP (802.1w) per VLAN. Rapid PVST+ greatly
improves the detection of indirect failures or linkup restoration events over
classic spanning tree (802.1D).
Core Layer
59
Although this architecture is built without any Layer 2 loops, you must still
enable spanning tree. By enabling spanning tree, you ensure that if any
physical or logical loops are accidentally configured, no actual layer 2 loops
occur.
spanning-tree mode rapid-pvst
Step 4: Enable Unidirectional Link Detection (UDLD).
UDLD is a Layer 2 protocol that enables devices connected through fiberoptic or twisted-pair Ethernet cables to monitor the physical configuration
of the cables and detect when a unidirectional link exists. When UDLD
detects a unidirectional link, it disables the affected interface and alerts you.
Unidirectional links can cause a variety of problems, including spanning-tree
loops, black holes, and non-deterministic forwarding. In addition, UDLD
enables faster link failure detection and quick reconvergence of interface
trunks, especially with fiber, which can be susceptible to unidirectional
failures.
udld enable
Step 5: Set EtherChannels to use the traffic source and destination IP
address when calculating which link to send the traffic across. This normalizes the method in which traffic is load-shared across the member links
of the EtherChannel. EtherChannels are used extensively in this design
because of their resiliency capabilities.
port-channel load-balance src-dst-ip
Step 6: Configure DNS for host lookup.
At the command line of a Cisco IOS device, it is helpful to be able to type a
domain name instead of the IP address for a destination.
ip name-server 10.4.48.10
Step 7: Configure device management protocols.
Secure HTTP (HTTPS) and Secure Shell (SSH) are more secure replacements for the HTTP and Telnet protocols. They use Secure Sockets Layer
(SSL) and Transport Layer Security (TLS) to provide device authentication
and data encryption.
The SSH and HTTPS protocols enable secure management of the LAN
device. Both protocols are encrypted for privacy, and the nonsecure protocols, Telnet and HTTP, are turned off.
August 2012 Series
Specify the transport preferred none on vty lines to prevent errant connection attempts from the CLI prompt. Without this command, if the ip
name server is unreachable, long timeout delays may occur for mistyped
commands.
ip domain-name cisco.local
ip ssh version 2
no ip http server
ip http secure-server
!
line vty 0 15
transport input ssh
transport preferred none
Step 8: Enable Simple Network Management Protocol (SNMP) in order
to allow the network infrastructure devices to be managed by a Network
Management System (NMS), and then configure SNMPv2c both for a readonly and a read-write community string.
snmp-server community cisco RO
snmp-server community cisco123 RW
Step 9: If your network operational support is centralized, you can increase
network security by using an access list to limit the networks that can access
your device. In this example, only devices on the 10.4.48.0/24 network will be
able to access the device via SSH or SNMP.
access-list 55 permit 10.4.48.0 0.0.0.255
line vty 0 15
access-class 55 in
!
snmp-server community cisco RO 55
snmp-server community cisco123 RW 55
Caution
If you configure an access-list on the vty interface you may lose
the ability to use ssh to login from one router to the next for hopby-hop troubleshooting.
Core Layer
60
Step 10: Configure local login and password.
The local login account and password provides basic device access authentication to view platform operation. The enable password secures access
to the device configuration mode. By enabling password encryption, you
prevent the use of plain text passwords when viewing configuration files.
username admin password c1sco123
enable secret c1sco123
service password-encryption
aaa new-model
By default, https access to the switch will use the enable password for
authentication.
Step 11: If you want to reduce operational tasks per device, configure
centralized user authentication by using the TACACS+ protocol to authenticate management logins on the infrastructure devices to the Authentication,
Authorization and Accounting (AAA) server.
As networks scale in the number of devices to maintain, there is an operational burden to maintain local user accounts on every device. A centralized
Authentication, Authorization and Accounting (AAA) service reduces operational tasks per device and provides an audit log of user access for security
compliance and root cause analysis. When AAA is enabled for access
control, all management access to the network infrastructure devices (SSH
and HTTPS) is controlled by AAA.
TACACS+ is the primary protocol used to authenticate management
logins on the infrastructure devices to the AAA server. A local AAA user
database is also defined on each network infrastructure device to provide
a fallback authentication source in case the centralized TACACS+ server is
unavailable.
aaa authentication login default group tacacs+ local
aaa authorization exec default group tacacs+ local
aaa authorization console
ip http authentication aaa
tacacs-server host 10.4.48.15 key SecretKey
Reader Tip
The AAA server used in this architecture is Cisco Authentication
Control System. Configuration of ACS is discussed in the Device
Management Using ACS Deployment Guide.
Step 12: Configure a synchronized clock by programming network devices
to synchronize to a local NTP server in the network. The local NTP server
typically references a more accurate clock feed from an outside source.
Configure console messages, logs, and debug output to provide time
stamps on output, which allows cross-referencing of events in a network..
ntp server 10.4.48.17
ntp update-calendar
!
clock timezone PST -8
clock summer-time PDT recurring
!
service timestamps debug datetime msec localtime
service timestamps log datetime msec localtime
Procedure 3
Configure the core switch global settings
Step 1: Configure the in-band management interface.
The loopback interface for Cisco Layer 3 devices is a logical interface
that is always reachable as long as the device is powered on and any IP
interface is reachable to the network. Layer 3 process and features are also
bound to the loopback interface to ensure resiliency of the processes. The
loopback address is commonly a host address with a 32-bit address mask
and has been allocated out of the core network address range. This example
includes the ip pim sparse-mode command that will be explained further in
Procedure 4.
interface loopback 0
ip address [ip address] 255.255.255.255
ip pim sparse-mode
August 2012 Series
Core Layer
61
snmp-server trap-source Loopback 0
ip ssh source-interface Loopback 0
ip pim register-source Loopback0
ip tacacs source-interface Loopback0
ntp source Loopback0
Step 3: Configure IP unicast routing
Enable EIGRP for the IP address space that the network will be using and
disable auto summarization of the IP networks. If needed for your network,
you can enter multiple network statements. The Loopback 0 IP address is
used for the EIGRP router ID to ensure maximum resiliency.
router eigrp 100
network 10.4.0.0 0.1.255.255
no auto-summary
eigrp router-id [ip address of loopback 0]
Procedure 4
Configure IP Multicast routing
IP Multicast allows a single IP data stream to be sent from a single source
to multiple receivers and be replicated by the infrastructure (that is, routers and switches). Using IP Multicast is much more efficient than multiple
unicast streams or a broadcast stream that would propagate everywhere.
IP Telephony Music on Hold and IP Video Broadcast Streaming are two
examples of IP Multicast applications.
To receive a particular IP Multicast data stream, end hosts must join a
multicast group by sending an Internet Group Management Protocol (IGMP)
message to their local multicast router. In a traditional IP Multicast design,
the local router consults another router in the network that is acting as an RP
to map receivers to active sources so they can join their streams.
The RP is a control-plane operation that should be placed in the core of the
network or close to the IP Multicast sources on a pair of Layer 3 switches or
routers. In this design, which is based on pim sparse mode multicast operation, Cisco uses Anycast RP to provide a simple yet scalable way to provide a
highly resilient RP environment when two separate devices are used as RPs.
August 2012 Series
Step 1: Enable PIM.
Enable IP Multicast routing on the platforms in the global configuration
mode.
ip multicast-routing
Step 2: Configure loopback interface for RP.
To enable Anycast RP operation, the first step is to configure a second
loopback interface on each of the core switches. The key is that this second
loopback interface has the same IP address on both core switches and
uses a host address mask (32 bits). All routers then point to this common IP
address on loopback 1 for the RP. You configure the RP address from the
core IP address space.
interface Loopback 1
ip address 10.4.40.252 255.255.255.255
ip pim sparse-mode
Step 3: Configure Multicast Source Discovery Protocol (MSDP).
The final step for the Anycast RP configuration is to enable Multicast Source
Discovery Protocol (MSDP) to run between the two core RP switches.
Figure 29 - MSDP overview
Source 1
Source 2
RP 1
RP 2
MSDP
SA Message
10.4.40.253
SA Message
10.4.40.254
2112
Step 2: Configure the SNMP and SSH processes to use the loopback
interface address for optimal resiliency:
To enable MSDP, you must use unique addresses at each end of the link.
Therefore, you will use the loopback 0 addresses of each core router to
configure the MSDP session.
On core switch #1:
ip msdp peer 10.4.40.253 connect-source Loopback0
ip msdp originator-id Loopback0
! The IP address listed above is the core switch #2 loopback
Core Layer
62
On core switch #2:
ip msdp peer 10.4.40.254 connect-source Loopback0
ip msdp originator-id Loopback0
! The IP address listed above is the core switch #1 loopback
The MSDP configuration is complete and convergence around a failed RP
is now as fast as the unicast routing protocol (EIGRP) convergence. You will
see the MSDP protocol session activate later on as you enable the routing
links between the core switches and the distribution layer blocks establishing Layer 3 connectivity.
%MSDP-5-PEER_UPDOWN: Session to peer 10.4.40.253 going up
Every Layer 3 switch and router must know the address of the IP Multicast
RP, including the core switches that are serving as the RP. This design uses
AutoRP to announce candidate RPs, which are the core switches, to the rest
of the network.
Step 4: Configure AutoRP candidate RPs.
The send-rp-announce command in conjunction with the group-list option
advertises the RP address, with the multicast range the device is willing to
serve, as a candidate RP to the AutoRP mapping agents.
access-list 10 permit 239.1.0.0 0.0.255.255
ip pim send-rp-announce Loopback1 scope 32 group-list 10
Step 5: Configure AutoRP mapping agent.
The AutoRP mapping agent listens for candidate RPs and then advertises
to the rest of the network the list of available RPs. The send-rp-discovery
command enables the core switches to act as AutoRP mapping agents.
ip pim send-rp-discovery Loopback0 scope 32
Step 6: Configure devices to listen to AutoRP announcements.
All Layer 3 switches and routers in the organization, including the RPs, must
be configured to listen to the AutoRP announcements from the mapping
agents.
ip pim auto-rp listener
Cisco Catalyst 6500 uses the command ip pim autorp listener.
In the event you add a core layer to your existing network and the RP is
currently configured on a distribution layer, you may want to move the RP to
the core.
With AnyCast RP, you can move the RP to a new location by programming
August 2012 Series
the RP address on the loopback 1 interfaces at the new location, and enable
and establish IP Multicast and MSDP peering.
All remote routers should still point to the same RP address, which simplifies
the move and reduces disruption to the IP Multicast environment.
All Layer 3 interfaces in the network must be enabled for sparse mode
multicast operation.
ip pim sparse-mode
Procedure 5
Connect to distribution layer
In this design, links in the core layer are configured as point-to-point Layer 3
routed links or Layer 3 routed EtherChannels. If you are using Cisco Catalyst
6500 VSS 4T system in the distribution layer, Cisco recommends that all
peer-connected links are EtherChannel links. EtherChannel to the Catalyst
6500 VSS provides for optimal forwarding because a packet that is received
on the switch will be forwarded out a link on that same switch in normal
operation instead of traversing the VSL link.
Other benefits of EtherChannel to any single physical or logical device are that
it makes it easier for you to grow bandwidth without changing the topology and
that a single link failure uses EtherChannel recovery versus using ECMP or a
routing topology change to reroute the data flows for fastest recovery.
Since the core links are point-to-point routed links, use 30-bit IP address
subnets and masks and do not use Switched Virtual Interfaces (SVI).
Step 1: Configure the Layer 3 interface.
If you are using an EtherChannel to connect to a distribution layer platform,
the interface type will be portchannel and the number must match the
channel-group number you will configure in Step 2. When configuring a
Layer 3 EtherChannel the logical port-channel interface is configured prior
to configuring the physical interfaces associated with the EtherChannel.
interface [interface type] [number]
description Link to {your device here}
no switchport
ip address [ip address] [mask]
ip pim sparse-mode
logging event link-status
carrier-delay msec 0
no shutdown
Core Layer
63
Step 2: If you are connecting to the same distribution layer switch with
multiple links, you can use a portchannel for added bandwidth over a single
logical link. Configure the physical interfaces to tie to the logical port channel by using the channel-group command. The number for the port channel
and channel group will match.
Also, apply the egress QoS macro that was defined in the platform configuration procedure to ensure traffic is prioritized appropriately.
Tech Tip
The Catalyst 6500 has two egress QoS macros, EgressQoS which
is used for Gigabit Ethernet ports, and EgressQoSTenGig which is
used for Ten Gigabit Ethernet ports. All other Cisco SBA distribution layer platforms have a single egress QoS macro that applies
to Gigabit and Ten Gigabit Ethernet ports.
interface [interface type] [port 1]
description Link to {your device here} port 1
interface [interface type] [port 2]
description Link to {your device here} port 2
!
interface range [interface type] [port 1], [interface type]
[port 2]
no switchport
macro apply EgressQoS
channel-protocol lacp
channel-group [number] mode active
logging event link-status
logging event trunk-status
logging event bundle-status
August 2012 Series
Step 3: Save the running configuration that you have entered so it will
be used as the startup configuration file when your switch is rebooted or
power-cycled.
copy running-config startup-config
Example
PortChannel 20
10.4.40.17/30
Ten 4/1
Ten 5/1
2113
If the interface type is not a port-channel, then an additional command
macro apply EgressQoS must also be configured on the interface.
interface Port-channel 20
description EtherChannel link to Distribution Switch
no switchport
ip address 10.4.40.17 255.255.255.252
ip pim sparse-mode
no shutdown
!
interface range TenGigabitEthernet 4/1, TenGigabitEthernet 5/1
description EtherChannel link to Distribution Switch
no switchport
macro apply EgressQoSTenGig
carrier-delay msec 0
channel-group 20 mode on
logging event link-status
logging event trunk-status
logging event bundle-status
no shutdown
!
Core Layer
64
Appendix A: Product List
LAN Access Layer
Functional Area
Product Description
Part Numbers
Software
Modular Access Layer
Switch
Cisco Catalyst 4507R+E 7-slot Chassis with 48Gbps per slot
WS-C4507R+E
3.3.0.SG(15.1-1SG)
Cisco Catalyst 4500 E-Series Supervisor Engine 7L-E
WS-X45-SUP7L-E
Cisco Catalyst 4500 E-Series 48 Ethernet 10/100/1000 (RJ45) PoE+ ports
WS-X4648-RJ45V+E
IP Base
Cisco Catalyst 4500 E-Series 48 Ethernet 10/100/1000 (RJ45) PoE+,UPoE
ports
WS-X4748-UPOE+E
Cisco Catalyst 3750-X Series Stackable 48 Ethernet 10/100/1000 PoE+ ports
WS-C3750X-48PF-S
15.0(1)SE2
Cisco Catalyst 3750-X Series Stackable 24 Ethernet 10/100/1000 PoE+ ports
WS-C3750X-24P-S
Cisco Catalyst 3750-X Series Two 10GbE SFP+ and Two GbE SFP ports
network module
C3KX-NM-10G
IP Base
Cisco Catalyst 3750-X Series Four GbE SFP ports network module
C3KX-NM-1G
Cisco Catalyst 3560-X Series Standalone 48 Ethernet 10/100/1000 PoE+
ports
WS-C3560X-48PF-S
Cisco Catalyst 3560-X Series Standalone 24 Ethernet 10/100/1000 PoE+
ports
WS-C3560X-24P-S
Cisco Catalyst 3750-X Series Two 10GbE SFP+ and Two GbE SFP ports
network module
C3KX-NM-10G
Cisco Catalyst 3750-X Series Four GbE SFP ports network module
C3KX-NM-1G
Cisco Catalyst 2960-S Series 48 Ethernet 10/100/1000 PoE+ ports and Two
10GbE SFP+ Uplink ports
WS-C2960S-48FPD-L
Cisco Catalyst 2960-S Series 48 Ethernet 10/100/1000 PoE+ ports and Four
GbE SFP Uplink ports
WS-C2960S-48FPS-L
Cisco Catalyst 2960-S Series 24 Ethernet 10/100/1000 PoE+ ports and Two
10GbE SFP+ Uplink ports
WS-C2960S-24PD-L
Cisco Catalyst 2960-S Series 24 Ethernet 10/100/1000 PoE+ ports and Four
GbE SFP Uplink ports
WS-C2960S-24PS-L
Cisco Catalyst 2960-S Series Flexstack Stack Module
C2960S-STACK
Stackable Access Layer
Switch
Standalone Access Layer
Switch
Stackable Access Layer
Switch
August 2012 Series
15.0(1)SE2
IP Base
15.0(1)SE2
LAN Base
Appendix A: Product List
65
LAN Distribution Layer
Functional Area
Product Description
Part Numbers
Software
Modular Distribution Layer
Virtual Switch Pair
Cisco Catalyst 6500 E-Series 6-Slot Chassis
WS-C6506-E
15.0(1)SY1
Cisco Catalyst 6500 VSS Supervisor 2T with 2 ports 10GbE and PFC4
VS-S2T-10G
Cisco Catalyst 6500 16-port 10GbE Fiber Module w/DFC4
WS-X6816-10G-2T
IP services
Cisco Catalyst 6500 24-port GbE SFP Fiber Module w/DFC4
WS-X6824-SFP
Cisco Catalyst 6500 4-port 40GbE/16-port 10GbE Fiber Module w/DFC4
WS-X6904-40G-2T
Cisco Catalyst 6500 4-port 10GbE SFP+ adapter for WX-X6904-40G module
CVR-CFP-4SFP10G
Cisco Catalyst 4507R+E 7-slot Chassis with 48Gbps per slot
WS-C4507R+E
3.3.0.SG(15.1-1SG)
Cisco Catalyst 4500 E-Series Supervisor Engine 7-E, 848Gbps
WS-X45-SUP7-E
Cisco Catalyst 4500 E-Series 24-port GbE SFP Fiber Module
WS-X4624-SFP-E
Enterprise Services
Cisco Catalyst 4500 E-Series 12-port 10GbE SFP+ Fiber Module
WS-X4712-SFP+E
Modular Distribution Layer
Switch
Stackable Distribution Layer Cisco Catalyst 3750-X Series Stackable 12 GbE SFP ports
Switch
Cisco Catalyst 3750-X Series Two 10GbE SFP+ and Two GbE SFP ports
network module
WS-C3750X-12S-E
15.0(1)SE2
C3KX-NM-10G
IP Services
Cisco Catalyst 3750-X Series Four GbE SFP ports network module
C3KX-NM-1G
Functional Area
Product Description
Part Numbers
Software
Modular Core Layer Switch
Cisco Catalyst 6500 E-Series 6-Slot Chassis
WS-C6506-E
15.0(1)SY1
Cisco Catalyst 6500 VSS Supervisor 2T with 2 ports 10GbE and PFC4
VS-S2T-10G
Cisco Catalyst 6500 24-port GbE SFP Fiber Module w/DFC4
WS-X6824-SFP
IP services
Cisco Catalyst 6500 8-port 10GbE Fiber Module w/ DFC4
WS-X6908-10G-2T
LAN Core Layer
August 2012 Series
Appendix A: Product List
66
Appendix B: Changes
This appendix summarizes the changes to this guide since the previous
Cisco SBA series.
• We combined into this guide the LAN deployment guidance formerly
published in the following guides:
◦◦
Cisco SBA for Midsize Organizations—Borderless Networks
Foundation Deployment Guide
◦◦
Cisco SBA for Enterprise Organizations—Borderless Networks LAN
Deployment Guide
• We moved wireless LAN to a separate guide, the Wireless LAN
Deployment Guide.
• For the Cisco Catalyst 6500 Series Switch, we did the following:
◦◦
Updated QoS configurations for Catalyst 6500 to comply with newer
IOS code versions.
◦◦
Changed the QoS macro for Ten Gigabit Ethernet to
EgressQoSTenGig.
◦◦
Changed the QoS macro for Gigabit Ethernet to EgressQoS.
◦◦
We tested the WS-X6904-40G-2T 40Gb/10Gb Ethernet module in
the distribution layer for 10-Gb Ethernet access layer aggregation.
• For the Cisco Catalyst 4500 Series Switch, we updated QoS policy for
access edge QoS policy to accommodate speeds from 10Mb, 100Mb,
and Gigabit Ethernet connected devices.
• For the Cisco Catalyst 3750-X, 3560-X, and 2960-S Series Switches, we
updated QoS policy for the Egress QoS macro to reference queue-set 1
to correct a configuration error.
• We updated centralized user authentication template to the newer
method which allows IPv4 and IPv6 TACACS+ server definition. The older
method will be deprecated from Cisco IOS overtime.
• In the distribution layer, we changed the spanning-tree root primary
command to include all VLANs—for simplicity and reduced operational
errors. You can do this because the design never passes Layer 2 VLANs
beyond the distribution layer and the distribution layer should be the root
for all connected access layer switches.
• Added more configuration examples and improved readability.
August 2012 Series
Appendix B: Changes
67
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Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content
is unintentional and coincidental.
© 2012 Cisco Systems, Inc. All rights reserved.
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