Configuring a loopback interface on a Cisco router

Question

I have Router 1 with the following interfaces:

• FA0/1: 192.168.9.193 255.255.255.224
• S0/0/0: 192.168.9.129 255.255.255.224
• S0/0/1: 192.168.9.161 255.255.255.224

This is for my assignment at university, there should be a computer connected to the FA0/1 interface of this router, the computer should have these details:

• IP: 192.168.9.222
• Subnet: 255.255.255.224
• Default Gateway:192.168.9.193.

As I don't have a computer available to connect to the router I was told to use a loopback interface to virtualise this.

Please help me on setting up this loopback.

Solution 1

Just do as you would do with a regular interface:

enable 
conf t 
int loopback 1
ip address 192.168.9.193 255.255.255.224 
no shut

Now enable routing for that subnet on your router and you are all set.

Solution 2

Another solution would be to disable the keepalive on the FastEthernet to artificially bring it up :

Router(config)# interface FastEthernet0/1
Router(config)# no keepalive

The interface will now show up/up even if there is no cable plugged on the interface. Therefore your router will be reachable from the wan on his Fa0/1 (192.168.9.193) IP address.

Comments

[Bill Weiss]

A loopback interface and an attached computer aren't the same kind of thing. What is the actual goal?

[Jack Brown]

THE Ip used for FA0/1 is 192.168.9.193 255.255.255.224 says the loopback overlaps it....

[Lucas Kauffman]

Updated, sorry it's getting late, is it working ?