OSPF loopback Advertisment

[msbharadwaja]

Hi Everyone,

Please let me know that when we advertise loopback in OSPF why it will advertise as /32 in the ospf routing table.

Thanks,

Krishna.

[Deepak Kumar]

Hi, 

Please add a command to lookback interface

ip ospf network point-to-point

Regards,

Deepak Kumar 

[msbharadwaja]

Hi Deepak,

Thanks for you reply !!

I understood, But why only OSPF will advertise as /32 but not any other protocols like Eigrp ?

[Deepak Kumar]

Hi,

I read RFC2328 and found some useful information on this:

If the state of the interface is Loopback, add a Type 3
                link (stub network) as long as this is not an interface
                to an unnumbered point-to-point network.  The Link ID
                should be set to the IP interface address, the Link Data
                set to the mask 0xffffffff (indicating a host route),
                and the cost set to 0.

The /32 advertisement limitation of loopback interfaces can be overcome by either changing OSPF network type to point-to-point or creating the summary route with the desired mask.

Regards,

Deepak Kumar