[c-nsp] Loopback Advertise in OSPF

[Christian Meutes]

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