Loopback Interfaces

[Ally0000]

Hi there

I am looking for some information on loopback interfaces on Cisco routers. I have checked cisco.com (I have full access) and quite extensively on google with no real results. I know that they are used by certain dynamic routing protocols as the loopback interface never goes down, but I can't find any good information on where, when and why to really use them.

Any links would be fantastic.

Thanks
Ally

 

[computerhighguy]

Heres a link talking about using a loopback adapter for access servers to summarize routes to the backbone.

http://www.cisco.com/en/US/partner/...s_configuration_example09186a0080094a49.shtml

It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)

 

[akonwar]

cannot see the information link it requires user authentication

 

[computerhighguy]

http://www.cisco.com/en/US/products...s_configuration_example09186a0080094a49.shtml

It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)

 

[pmesjar]

OSPF and BGP use loopback interfaces extensively. I have also seen "NAT on the stick" feature to use loopbacks.

NAT on the stick:

http://www.cisco.com/warp/public/556/nat-on-stick.html

For BGP:

http://www.cisco.com/warp/public/459/23.html

For OSPF:
Here you need to go a little deeper into theory of OSPF operation. I just say that every router has OSPF Router ID, that identifies it to OSPF area. This router ID is 32bits and is taken from highest loopback configured on router.

Peter Mesjar
CCNP, A+ certified
pmesjar@centrum.sk

"The only true wisdom is in knowing you know nothing.

 

[Ally0000]

Thanks very much for all your comments and links, I had to go on-site yesterday so I'm sorry for not replying sooner. I'll get this all figured out.

Ally