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Data Forwarding

Basic Router Configuration

Overview

In this session, we sill be looking at Review : router backplane

Ethernet, console and serial interfaces Configuring router interfaces

Ethernet and serial interface Viewing router configurations

Using show commands Testing network connectivity

Using ping command

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Addressing - Review

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What is Routing?

Routing - Selecting the correct path towards destination Build Routing table for

path selection Two methods

Static Dynamic

Router

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0111

value in arrivingpacket’s header

routing algorithm

local forwarding table

header value output link

0100010101111001

3221

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Routers –Interfaces

Routers have LAN interfaces

Ethernet interfaces: Have MAC Addresses IP addresses

WAN interfaces Serial interfaces Have IP addresses

Serial 0192.168.10.1 255.255.255.252

Ethernet 1 172.16.2.1/ 255.255.255.0 MAC: 0abbccddeeff

Ethernet 0172.16.1.1/ 255.255.255.0

MAC: 0cddeeffaabb

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Review: Cisco Router backplane Identify the different interfaces on router

Interface 1 Interface 2 Interface 3 Interface 4

Serial interface

console interfaceEthernet interface

Interface 1 Interface 2

Interface 3

Interface 4

Router Components

RAM – holds packet buffers, routing table, running-config is stored in RAM,

ROM – starts and maintains the router Flash memory – holds the IOS;

is not erased when the router is reloaded; is an EEPROM [Electrically Erasable Programmable Read-Only Memory]

NVRAM – Non-Volatile RAM - holds router configuration; is not erased when router is reloaded

Where Is The Configuration?

Can also be stored in more permanent places: External hosts, using TFTP (Trivial File Transfer Protocol) In flash memory in the router

Copy command is used to move it around

copy run start copy run tftp copy start tftp copy tftp start copy flash start copy start flash

Identify network boundaries

128.143.100.32/24 255.255.255.0

128.143.102.32/24 255.255.255.0

128.143.101.32/24 255.255.255.0

128.143.10.33/24 255.255.255.0

R R

•Can you identify different networks and network addresses ?•Identify network class •What is the maximum number of hosts that can be hosts can be connected on each of these networks?

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Review: Establishing a Hyper-terminal Session

• All Cisco routers include an EIA/TIA-232 asynchronous serial console port (RJ-45).

• How do you connect to router to configure?

• Router configured from PC connected to router console port using a rollover cable

• Rollover cable has•Serial interface adapter on one side and •RJ45 adapter on the other

PC

Serial adapter

RJ45 adapter

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Routing Types

Example: Static Routing

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Connections to the Router- cables

Connections of a Router for Ethernet 2 types of cables can be used:

Straight through and Cross-over Straight through used to connect

dissimilar devices Switch-to-Router, Switch-to-PC,

Cross-over used to connect

similar devices: Switch-to-Switch, Router to PC (Host) PC-to-PC, Switch-to-Hub, Hub-to-Hub, Router-to-Router

Cross-over Straight-thru

Straight-thru

Logging Into The Router Connect router to console port or telnet to router

– router>– router>enable– password– router#– router#?

Configuring the router– Terminal (entering the commands directly)– router# configure terminal– router(config)#

USER MODE PROMPT

PRIVILEDGED MODE PROMPT

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Configuring router Interfaces

-By default all interfaces are down Ethernet Serial

Interface configured with IP address and subnet mask

No Shutdown command used to enable the interface

Ethernet interface

New Router Configuration Process

Load configuration parameters into RAM Router#configure terminal

Personalize router identification Router#(config)hostname RouterA

Assign access passwords RouterA#(config)line console 0 RouterA#(config-line)password cisco RouterA#(config-line)login

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To configure an Ethernet interface -Enter interface configuration mode (config) -Enter IP address and subnet mask -Enter no shutdown command Example:

-R2(config)#interface fastethernet 0/0 -R2(config-if)#ip address 172.16.1.1 255.255.255.0 -R2(config-if)#no shutdown

Configuring Interfaces –Ethernet Interface

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Configuring Interfaces – Serial Interface

Configuring a Serial interface -Enter interface configuration mode -Enter in the ip address and subnet mask -Enter in the no shutdown command

Example: -R1(config)#interface serial 0/0 -R1(config-if)#ip address 172.16.2.1 255.255.255.0 -R1(config-if)#no shutdown

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Configuring serial links in a lab environment Serial Interfaces require a clock signal to control the timing of

the communications One end of serial interface is DCE end and other end is DTE

end configure timing on the DCE end of serial interface.

R1# show interface serial 0/0

If it is DCE interface then configure clock rate -R1(config)#interface serial 0/0 -R1(config-if)#clock rate 64000

Serial Interface – setting clock rate

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Verify configuration Use show commands

-Show interfaces fastEthernet 0/0 -Show ip interface brief -Show running-config

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Testing the network connectivity

To check the connectivity Run ‘ping’ command

Between Host 1 and Host 3 Host 1 and router Host 2 and router Host 3 and router

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Review: Default Gateway

When a LAN is connected to a Router, Default Gateway is the address of router interface connected to that LAN.

The IP address and subnet mask is on the same network as the hosts on that network

Router

LAN

Router

Default Gateway

Global Configuration

Static route creation:

IP route <n.n.n.n> <m.m.m.m> <g.g.g.g> n.n.n.n = network block m.m.m.m = network mask denoting block size g.g.g.g = next hop gateway destination packets

are sent to

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Static Routes

The NO Command

Used to reverse or disable commands e.g

ip domain-lookup no ip domain-lookup router ospf 1 no router ospf 1 ip address 1.1.1.1 255.255.255.0 no ip address

Looking At The Configuration

Use “show running-configuration” to see the current configuration

Use “show startup-configuration” to see the configuration in NVRAM, that will be loaded the next time the router is rebooted or reloaded

Getting Online Help IOS has a built-in help facility; use “?” to get a list of

possible configuration statements

“?” after the prompt lists all possible commands: router#?

“<partial command> ?” lists all possible subcommands, e.g.: router#show ? router#show ip ?

Getting Online Help

This also works in configuration mode: router(config)#ip a? accounting-list accounting-threshold

accounting-transits address-pool alias as-path

router(config)#int e0/0 router(config-if)#ip a? access-group accounting address

Getting Lazy Help TAB character will complete a partial word

hostel-rtr(config)#int<TAB> hostel-rtr(config)#interface et<TAB> hostel-rtr(config)#interface ethernet 0 hostel-rtr(config-if)#ip add<TAB> hostel-rtr(config-if)#ip address ...

n.n.n.n m.m.m.m Not really necessary; partial commands can be used:

router#conf t router(config)#int e0/0 router(config-if)#ip addr n.n.n.n

Deleting Your Router’s Configuration

To delete your router’s configuration Router#erase startup-config Router#reload

Router will startup again, but in setup mode, since startup-config file does not exists

How many Static Routes?

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Conclusion

Today we learnt to Configure router interfaces

Ethernet and Serial Set clock rate on serial interface Set up and tested the testbed network

Design IP addressing Configure ethernet interfaces Verified configurations used ping to test network

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