[c-nsp] Loopback Advertise in OSPF

[David Barak]

Hi,

I believe the initial poster was talking about normal loopbacks- ther kind you'd use for network management, ibgp peering, or perhaps anycast.  In that case, you needn't be worried about spf churn, because they're yours, and not going down, and you would want the routes generated to be internal routes (so that the metrics and SPF can do their job).  In that case, nothing beats a network statement + passive-interface.

I prefer to use passive default, and then only enable the correct interfaces.

-David

Christian Meutes wrote: 
> Hi,
> --On Mittwoch, 27. Februar 2008 10:56 +0000 Phil Mayers 
> <p.mayers at imperial.ac.uk> wrote:
>>   * the routes generates are OSPF E2 which since they are at the leaves
>> of the tree, churn in them does not require an SPF recompute - provided
>> "ispf" is specified on the OSPF process.
> Not exactly, external LSAs never trigger SPF, therefore iSPF only smallers
> SPF computation-time when a 'topology'-LSA(1/2) would have caused a full 
> SPF run, e.g. when prefix/metric changes on an OSPF-enabled interface on a
> stub-node, and not when a redistributed prefix changes.
>> The major disadvantages that I can see are:
>>
>>   * because the routes are E2s it increases the number of LSAs - which
>> obviously went away with the move to MPLS/BGP
> The only disadvantage I can see in using external-LSAs.
> Christian
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