[c-nsp] OSPF for loopback interfaces - /32 instead of /29

Phil Mayers p.mayers at imperial.ac.uk
Tue Mar 6 06:51:43 EST 2007


Vincent De Keyzer wrote:
> Hello,
> 
>  
> 
> I am surprised of what I see: 
> 
>  
> 
> 1)     When I configure X.Y.Z.9/29 as IP for lo1 interface; I don't see the
> expected X.Y.Z.9/29 on a OSPF neighbouring router: I only see X.Y.Z.9/32.

That's pointless. Don't do it. The IP on a loopback should be a /32

> 
> 2)     If instead I put this address as *secondary* IP of lo0, then it works
> as expected (I see the /29 route on the neighbour).

If you want to pull up the /29 route, use a static to null0 or similar, 
which is both more robust and more clear in intent.

> Does that make sense to you? Is this the way loopback interfaces are
> supposed to work?

yes


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