1

2 Router

Basic Configuration Lab

s0

s1

172.16.10.1/16

172.16.10.2/16

e0

172.16.12.1/16

172.16.12.0/16

e0

172.16.11.1/16

172.16.11.0

RouterB

*

DCE

*

RouterA

/16

Objective:

In this lab you will configure a simple network to allow two routers to route packets between to
remote networks.

Requirements:

• Two Cisco routers with one Ethernet port and one serial port.

• Cisco IOS 10.0 or higher
• One PC for consoling into routers with terminal emulation software

• One serial cable

• One Cisco rollover cable

Setup:

Step 1: Physical Connections

Connect the following interfaces:

• Console: Connect your PC/terminal to the console port using a rollover cable and

HyperTerminal (9600-8-N-1-no flow)

• Ethernet: Connect Ethernet ports to a hub or a switch using a straight-through cable.

Use a cross-over cable if going directly from the PC’s NIC to the Ethernet (AUI) port on
the router using a transceiver.

• Serial: If going directly between two routers, don’t forget to connect one port via the

DTE cable and the other via the DCE cable.

Step 2: Boot up the routers

Just say “no” to use the setup mode (setup dialogue). The setup mode will only allow you to
configure the router with the basic features and not with any advanced features.

If asked if you would like to terminate the auto configuration; say “yes”.

Let the routers finish booting.

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Step 3: Host Name and Passwords

Begin your configuration with the hostname and passwords. This is to remind you of what
router you are configuring and now's the time to start thinking about router security.

RouterA

router>en
router#
router#config t
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#hostname RouterA (sets the router's name)
RouterA(config)#enable secret cisco (Sets the secret password
for the router)
RouterA(config)#line vty 0 4 (there are five concurrent
connections for the telnet ports coming into a Cisco 2500
router. We are setting the login password on all five of them)
RouterA(config-line)#login (This enables the router to require a
login password for a telnet session to the router)
RouterA(config-line)#password cisco (this sets the login
password for all 5 telnet sessions coming into the router as
cisco)
RouterA(config-line)#exit
RouterA(config)#^Z (This is the key combination of control+z
which takes you back to the privileged executive mode)
RouterA#

RouterB

router>en
router#
router#config t
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#hostname RouterB (sets the router's name)
RouterB(config)#enable secret cisco (Sets the secret password
for the router)
RouterB(config)#line vty 0 4 (there are five concurrent
connections for the telnet ports coming into a Cisco 2500
router. We are setting the login password on all five of them)
RouterB(config-line)#login (This enables the router to require a
login password for a telnet session to the router)
RouterB(config-line)#password cisco (this sets the login
password for all 5 telnet sessions coming into the router as
cisco)
RouterB(config-line)#exit

3

RouterB(config)#^Z (This is the key combination of control+z
which takes you back to the privileged executive mode)

FYI: Anytime you make a configuration change to a router and you come back to the
privileged exec mode you need to save your changes to NVRAM. This ensures that if the
router reboots, you won’t loose your changes which are in the running-config which is
volatile RAM. The following command(s) saves your changes to the startup-config.

RouterA#copy running-config startup-config
Or
RouterA# copy run start
Or
RouterA#wr me (short for write memory)

Step 4: Adding IP Addresses

Adding IP addresses, is a basic function of configuring routers. Below is an example of
configuring both an Ethernet and serial interface. For serial interface with the DCE cable you
will need to also add the clocking with the clockrate command. Get the IP addresses from the
network diagram.

RouterA

RouterA#config t
Enter configuration commands, one per line. End with CNTL/Z.
RouterA(config)#int e0
RouterA(config-if)#ip address 172.16.12.1 255.255.255.0
RouterA(config-if)# description LAN Network for RouterA
RouterA(config-if)# no shutdown
RouterA(config-if)#int s0
RouterA(config-if)#ip address 172.16.10.1 255.255.255.0
(RouterA will have the serial 0 with the DCE end of the serial
cable. The other partner will have serial1 with the DTE end of
the serial cable. Check the network diagram to confirm to see
who has what interface)
RouterA(config-if)#clockrate 250000 (DCE interface only which is
the s0 on RouterA)
RouterA(config-if)#no shutdown
RouterA(config-if)#description Network connection to RouterB

RouterB

RouterB#config t
Enter configuration commands, one per line. End with CNTL/Z.
RouterB(config)#int e0
RouterB(config-if)#ip address 172.16.11.1 255.255.255.0
RouterB(config-if)# description LAN Network for RouterB
RouterB(config-if)# no shutdown

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RouterB(config-if)#int s1
RouterB(config-if)#ip address 172.16.10.2 255.255.255.0
RouterB(config-if)#no shutdown
RouterB(config-if)#description Network connection to RouterA

Once both routers are configured properly, you should be able to use the
ping command and ping the interface e0 on each of the routers from the
neighboring router.

If you do a show ip route on both routers and do not see the directly
connected interfaces in the routing table, they are either not
configured or they never came up.

Confirm that the IP addressing took and the interfaces came up by using
the show ip int and looking at the interfaces' status and ip address
configuration.

RouterA# show ip route
RouterA# show ip int

Do this on both routers.

Step 5a: Adding Dynamic Routing: RIP

For this router to participate in a dynamic routing using a dynamic routing protocol like RIP or
IGRP, you'll need to enable a routing protocol and advertise the directly connected networks that
want advertised.. We only advertise the classful network address, not the subnet mask of the
network.

RouterA

RouterA>en
RouterA#config t
Enter configuration commands, one per line. End with CNTL/Z.
RouterA(config)#router RIP
RouterA(config-router)#network 172.16.12.0

RouterB

RouterB>en
RouterB#config t
Enter configuration commands, one per line. End with CNTL/Z.
RouterB(config)#router RIP
RouterB(config-router)#network 172.16.11.0

FYI: We need to advertise the network, not any particular host. An example of that would
be enabling RIP on RouterB. We want the other router (RouterA) to know that any packet
destined for the network 172.16.11.0 can be sent to RouterB which has a directly connected

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entry in it’s routing table showing what interface to send the packet to; in this case its e0. If
you route to 172.16.11.1, all your every going to route to, is the e0 on RouterB and nothing
else.

Test your configuration to ensure that it is configured properly by pinging from router to
router. Check your routing table for entries that are preceded by a capital letter "R" to
ensure that you are receiving routing updates using RIP. Ensure that your partner has
finished configuring his router so that you can receive his updates. No updates, no ping.

Do a show ip protocol to see what routing protocol is configured on the routers.

Step 5b: Adding Dynamic Routing: IGRP

IGRP uses an autonomous system (AS) number or process id. This number must be the same on
all routers wanting to share IGRP routing updates or they don’t share. Turn RIP off before you
turn on IGRP. For this lab we'll be using an AS number of 100.

RouterA

RouterA>en
RouterA#config t
RouterA(config)#no router rip
RouterA(config)#router igrp 100
RouterA(config-router)#network 172.16.12.0 (again, just the
network portion of the IP for your Ethernet network, NO subnet
mask)

RouterB

RouterB>en
RouterB#config t
Enter configuration commands, one per line. End with CNTL/Z.
RouterB(config)#no router rip
RouterB(config)#router igrp 100
RouterB(config-router)#network 172.16.11.0 (again, your
Ethernet network IP NO Subnet Address)

Step 6: Adding Default Routes

Good candidates for default routes are routers which are known as the boundary router. This is a
router which is normally part of a stub network. Inside the stub network, the routers may be
participating in a dynamic routing using a protocol like RIP, but only a static default route is
needed to connect the stub network to the Internet.

6

RouterA

RouterA>en
RouterA#config t
RouterA(config)#ip route 0.0.0.0 0.0.0.0 172.16.10.2

RouterB

RouterB>en
RouterB#config t
RouterB(config)#ip route 0.0.0.0 0.0.0.0 172.16.10.1

Step 7: Adding Static Routes

A static route can be used for different reasons. One reason may be for a router to connect to
another router in a lab. You'll need to turn off all routing protocols before you configure the
router for static routing.

RouterA

RouterA>en
RouterA#config t
RouterA(config)#no router igrp 100
RouterA(config)#ip route 172.16.11.0 255.255.255.0 172.16.10.2

What we are saying here is: For RouterA to route to the network 172.16.11.0, go to the next hop
interface which is the serial1 (172.16.10.2) attached to RouterB. Since RouterB knows about the
directed connected Ethernet network of 172.16.11.0, it will have route for it in its routing table
proceeded by the letter "C". (See next example)

RouterB#sh ip route
(Output omitted)
172.16.0.0/24 is subnetted, 1 subnets
C 172.16.0.0 is directly connected, Ethernet0
RouterB#

RouterB

RouterB>en
RouterB#
RouterB#config t
RouterB(config)#no router igrp 100
RouterB(config)#ip route 172.16.12.0 255.255.255.0 172.16.10.1

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Step 8: Testing and Monitoring

At this point it is a good idea to start testing your network using various commands.
Perform the following on both routers.

RouterA# show ip route
RouterA# show ip interface brief (This command shows the IP and
status of all interface)
RouterA# show controller s0 (Shows whether or not the serial
cable is DCE or DTE.)
RouterA# ping ip-address
RouterA# trace ip-address
RouterA# debug ip rip (Remember to turn debug off when done, use
undebug all, no debug all or un all)
RouterA# terminal monitor (for using debug from a telnet
session, otherwise debug output will go to the console. Caution:
This will cause the debug output to go to all telnet sessions on
the router.)

Show commands
RouterA# terminal no monitor(To turn off monitoring during a
telnet session.)
RouterA# show cdp neighbors
RouterA# show ip protocols
RouterA# #show version
RouterA# #show flash
RouterA# show ip route (shows the routing table)
RouterA# show memory
RouterA# show stacks
RouterA# show buffers
RouterA# show arp
RouterA# show processes
RouterA# show processes cpu
RouterA# show tech-support

Step 9: Finishing up

Once you have your routers up and working you may wish to run some commands to make
working on Cisco routers easier and to stop some of the default annoying behavior of Cisco
routers.

RouterA(config)# ip host RouterB 172.16.10.2 (This configures
a host table entry for the name RouterB. So instead of having to
remember the IP of RouterB to ping it, you can now ping it using
its name, RouterB. It's the same as using a hosts file on a
computer. If you just type in RouterB and hit enter, the router
will assume you’re wanting to telnet into RouterB using port 23)

8

RouterA(config)# no ip domain-lookup (When there is no DNS
server and you miss spell a single word command, it will try to
do a DNS lookup using a broadcast address of 255.255.255.255. To
stop this lookup of a non-existent DNS server, we can turn off
the DNS lookup capability using this command.)

RouterA(config)# banner motd #!!!!Warning! Authorized Access
Only!!!!# (This message will be seen by anyone trying to logon
to your router. The # sign is known as a delimiting character
and is used to identify the text portion of the MOTD. Notice
that the actual message starts and ends with the delimiting
character)

RouterA(config)# no service-config (When you reboot a Cisco
router, the default behavior is to try and find a configuration
file on the network using a number of methods over a broadcast
address of 255.255.255.255. To stop this annoying behavior, Use
this command.)

RouterA(config)#no logging console (Each time you leave one
level of the router and return to the previous level or bring an
interface up, you get a read out on the console screen. If you
get busy typing and configuring the router this can be
distracting and annoying. Use this command to stop the logging
of messages to the console screen.)

And don’t forget to…
RouterA# show running-config
RouterA# copy running-config startup-config

Miscellaneous

RouterA#? (the question mark can be used by itself or follow at the end of any partial command
line to get the next part of the command syntax)

To have the router CLI finish typing a command for you, just type out a partial command and hit
the TAB key. An example would be typing out copy ru and hitting the TAB key. The router CLI
with finish the command as copy running-configuration. Now if you add st to that and hit the
tab key again, the CLI will add to your last command startup-configuration, making your entire
command copy running-configuration startup-configuration. This works because there is only
one command the begins with copy ru.

Editing Commands
Control-A: Moves to the beginning of the command line.
Control-E: Moves to the end of the command line.
Esc-B: Moves back one word.
Control F: Moves forward one character.
Control-B: Move back one character.

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Esc F: Moves forward one word.

History Commands
Control P or up arrow key - Recalls last (previous command.)
Control N or down arrow key - Recalls most recent command
Tab key: completes the entry.
RouterA# show history
RouterA# terminal history
RouterA# terminal editing
RouterA# no terminal editing

FYI: This lab was designed to show you how to configure basic routing between two
routers. If you would like to ping from one PC on one network (RouterA) to another PC on
the other network (RouterB), you would need to configure the PC on each network with a
host IP that belonged to the Ethernet network IP of each router. An example of that would
be that the first available IP for a PC on the Ethernet network of RouterB would be
172.16.11.2. We know that the ".1" is already in use for the e0 interface on

RouterB. The

subnet mask for the PC would have to be the same as the rest of the network; 255.255.0.0 and the
default gateway for the PC would be the e0 that connects the LAN to RouterB.

So if a PC needs to find something that is not local or located on its LAN, the DFGW will take the
request to the router by way of the Ethernet Interface that connects the LAN to the Router. An
example of that would be, if you ping a PC located on the Ethernet network of RouterB from
RouterA’s LAN, the return echo from the PC has to know how to get back to the network on
RouterA from which it came. Since the Ethernet network path on RouterA is known to RouterB
through a routing table entry, the DFGW on the PC will take the unknown request for the return
trip of the packet from the PC and send it to RouterB which will know what to do with it. No
default Gateway in the TCP/IP properties of the PC and the packet will just time out and the ping
attempt will be unsuccessful. Chances are the ping did reach the PC but the return echo did not
know how to find a way back.

10

End of Lab

11

Basic Router Configuration Lab

NoAnswers

s0

s1

172.16.10.1/16

172.16.10.2/16

e0

172.16.12.1/16

172.16.12.0/16

e0

172.16.11.1/16

172.16.11.0

RouterB

*

DCE

*

RouterA

/16

Objective:

In this lab you will configure a simple network to allow two routers to route packets between to
remote networks.

Requirements:

• Two Cisco routers with one Ethernet port and one serial port.

• Cisco IOS 10.0 or higher

• One PC for consoling into routers with terminal emulation software
• One serial cable

• One Cisco rollover cable

Setup:

Step 1: Physical Connections

Configure a console session to your router(s) from your PC.

Step 2: Boot up the routers

Do not use the setup mode (setup dialogue) or auto configuration to configure the router.

Let the routers finish booting.

Step 3: Host Name and Passwords

Begin your configuration with the hostnames and passwords for both routers.

Configure RouterA and RouterB with their correct hostnames.
Configure all telnet sessions on both routers with the password of cisco
Exit back to the privileged mode and save your current configuration

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Step 4: Adding IP Addresses

Configure the interfaces on both routers with the IPs as per the network diagram.
Set a description on all interface.
Set the clockrate on the DCE end of the serial cable with a clockrate of 250000.
Ensure the interfaces come up.

Step 5a: Adding Dynamic Routing: RIP

Configure both routers for dynamic routing using the routing protocol RIP.
Advertise the appropriate networks on both routers.

Check both routers to see if they are receiving RIP routing updates from each other.
Ensure connectivity between the routers by using the ping command.
Remove RIP before starting step 5b.

Step 5b: Adding Dynamic Routing: IGRP

Configure both routers to use the routing protocol IGRP.
Configure both routers to use the same AS number.
Advertise the appropriate networks on both routers.

Check both routers to see if they are receiving IGRP routing updates from each other.
Check to see what routing protocol the routers are using.
Ensure connectivity between the routers by using the ping command.
Remove IGRP before starting step 6.

Step 6: Adding Default Routes

Configure both routers with a default route to each other. Use the neighboring router as a smart
gateway of last resort.

Check to ensure that the routers have a default route.

Ensure connectivity between the routers by using the ping command and pinging the interface e0
on each router.

Step 7: Adding Static Routes

Configure both routers with static routes to each routers remote network. Tell the routers how to
find the path to each others Ethernet network.

Check to ensure that the routers have a static route.

Ensure connectivity between the routers by using the ping command and pinging the interface e0
on each router.

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Step 8: Optimize the router performance.

Create a host table entry on each router to be able to ping the name of the router in lieu of the IP
address.

Configure both routers to turn off ip domain-lookup so they do not try and use a DNS server.

Configure a MOTD on each router that warns of authorized access only.

Configure both router not to look for a network configuration when they startup.

Disable logging to the console screen on both routers.

Step 9:

Configure your PC(s) for connectivity on the network.

Ping from the PC connected on RouterA's Ethernet 0 network to the PC on the Ethernet 0 of
RouterB. If you only have one PC, ping the interface Ethernet 0 on the either router.

End of Lab