Getting Started Connected and Non

Getting Started Connected and Non
Getting Started
From TCP/IP functions to configurations
First step: planning
q For each host
•
•
•
•
q
Default gateway address
Name server address
Domain Name
Subnet mask
For new network, will the new network connect to
Internet?
m
m
Connected network – accessible to other networks
Non-connected network – not directly attached to the
Internet.
Getting Started
1-1
Connected and Non-connected
Networks
q
Not-connected networks
m
m
m
q
Private networks
Enterprise networks – interconnect various part of an
organization
Intranets – internal service application, such as web
servers, browsers
Why not connected networks
m
m
Security
Cost
• For example, Only for email Exceed the benefit
q
Mixed both types:
m
m
A non-connected enterprise network before firewall
A small connected network providing customer services
and proxy service
Getting Started
1-2
1
Basic Info
q Obtaining a IP
m Public IP, unique on Internet
m RPC 1918, private network numbers
• 10/8
• 172.16/12
• 192.168/16
q Can you access Internet if you are using
the private network numbers?
m
m
Network address translation (NAT)
Proxy server
Getting Started
1-3
NAT
q http://computer.howstuffworks.com/nat1.htm
Getting Started
1-4
2
NAT
q Static NAT - Mapping an unregistered IP
address to a registered IP address on a oneto-one basis. Particularly useful when a
device needs to be accessible from outside
the network.
In static NAT, the computer with the IP
address of 192.168.32.10 will always
translate to 213.18.123.110.
Getting Started
1-5
NAT
q
Dynamic NAT - Maps an unregistered IP address to
a registered IP address from a group of registered IP
addresses.
q
In dynamic NAT, the computer with the IP address
192.168.32.10 will translate to the first available
address in the range from 213.18.123.100 to
213.18.123.150.
Getting Started
1-6
3
NAT
q
Overloading - A form of dynamic NAT that maps
multiple unregistered IP addresses to a single
registered IP address by using different ports. This is
known also as PAT (Port Address Translation), single
address NAT or port-level multiplexed NAT.
q
In overloading, each computer on the private
network is translated to the same IP address
(213.18.123.100), but with a different port number
assignment.
q
Getting Started
1-7
How overloading works
Source
Computer
Source
Computer's
IP Address
Source
Computer's
Port
NAT Router's
IP Address
NAT Router's
Assigned
Port Number
A
192.168.32.10
400
215.37.32.203
1
B
192.168.32.13
50
215.37.32.203
2
C
192.168.32.15
3750
215.37.32.203
3
D
192.168.32.18
206
215.37.32.203
4
Getting Started
1-8
4
NAT
q Overlapping - When the IP addresses used
on your internal network are registered IP
addresses in use on another network, the
router must maintain a lookup table of these
addresses so that it can intercept them and
replace them with registered unique IP
addresses.
Getting Started
1-9
NAT
q
NAT is transparent
m
Proxy, end users have to configure it.
• Application based
q
Advantages:
m
m
m
q
Conserves IP
Reduce address spoofing
Eliminate the reconfigure when connecting to Internet
Disadvantages
m
m
m
m
Cost
Performance
Reliability
Security
Getting Started
1-10
5
Get a public address
q
How many do you need? RFC 2901.
m
m
m
m
q
Internet end user
High-volume end user
Internet Service Provider
Local Internet Registry
Work your way out from bottom :Local ISP ->
ISP’s upstream provider -> Internet registry,
which will need:
m
m
m
m
m
Detailed network topology
Routing plan
Subnetting plan
Formal commitment of resources – who to be blamed.
……
Getting Started
1-11
Getting Started
1-12
Get a public address
q Three-level Internet registry
m IANA http://www.iana.org/
m Regional Internet Registry
• APNIC www.apnic.net
• ARIN www.arin.net
• RIPE www.ripe.net
m
Local Internet Registry
q Get an IN-ADDR.ARPA domain
m Reverse domain – map IP to name
6
q Assign host addresses
m One address at a time
m Groups of addresses
m
m
Statically
Dynamically
• Many remote dial-in clients to PPP server
• Mobile systems
• Desktops
q Defining a Subnet Mask
m Topological reasons for subnetting:
• Overcoming distance limitations
• Interconnecting dissimilar physical networks
• Filtering traffic between networks
m
Organizational purpose
Getting Started
1-13
Planning Routing
q Two ways:
m Static routing table
m Dynamic routing table
q Guidelines for
m A network with no gateways to other TCP/IP
network
m A network with a single gateway
m A network with internal gateways to other
subnet and a single gateway to the world
m A network with multiple gateways to the world.
Getting Started
1-14
7
q
Getting Started
1-15
Routing Plan
q an autonomous system number (ASN)
m BGP requires ASN
q Could be
m ASN of your ISP
m Private one 64512-65535
m Get official ASN from Regional Internet
Registry
• you are ISP
• Multi-homed site
q Registering in a Routing Database
m Validate routing
Getting Started
1-16
8
Naming Service
q
Basic request for name service
m
m
m
q
Obtaining a Domain Name
m
m
m
q
Domain name
System’s hostname
Name server’s IP address.
Get one from your ISP
Apply for a domain name yourself
Check out http://www.icann.org http:/www.internic.net
for official registrars.
Before you register,
m
Names and IP addresses of two servers
•
master and slave
Getting Started
1-17
Getting Started
1-18
Choosing a hostname
q Unique within your domain.
q RFC 1178 guidelines:
m Use real words
m Use theme names
m Avoid using
•
•
•
•
•
project names,
personal names,
Acronyms
Numeric names
Technical jargon
9
Other Service
q File servers
m Provide clients hostnames of the NFS and
location, contents.
m showmount –e host
m showmount –a host
q Print Servers
m lp, lpd, samba, etc.
m IP, hostname and the name of printer
q Mail System
m Mail server
Getting Started
1-19
Communicate with Users
q All the info has to be passed to end
users/system administrators
q Configuration instructions
Getting Started
1-20
10
Summary
q Internet connection
q Base info for network
q Routing
q Network services
Next:
Action!
Getting Started
1-21
11
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