[c-nsp] HSRp and OSPF metrics
Ray Burkholder
ray at oneunified.net
Tue Nov 14 15:46:37 EST 2006
>
> Phil Mayers wrote:
> >>>
> >>> redistribute connected subnets
> >>>
> >>> Is that what you call "sourcing"?
> >>>
> >>
> >> No. That's redistributing and results in OSPF externals. I'm
> >> talking about using network statements to include the networks for
> >> interfaces that match the network/mask statements.
> >
> > If you don't have any OSPF peers on that network, why would
> you want
> > to do that?
> >
> > Bearing in mind that changes in externs do not cause an SPF
> recompute
> > because they are always at the leaves of the tree.
>
> Because if you source them, they can be included as stubs in
> the Router LSA. Redistributing results in multiple Type 4
> (Summary ASBR) and Type 5
> (External) LSAs. Further, SPF is cheap in terms of CPU
> cycles. LSA generation and flooding is expensive and is a
> network wide issue for all routers.
>
> I'd recommend reading "Optimal Routing Design" by Russ White,
> Don Slice, and Alvaro Retana. http://safari.ciscopress.com/1587051877
>
Also there are a number of documents at http://www.cisco.com/go/srnd that
provide good background on how to deal with this layer2/3 segmentation and
synchronization and timing.
Suggested document names include:
Campus Network Multilayer Architecture and Design Guidelines
High Availability Campus Network Design-Routed Access Layer using EIGRP or
OSPF
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