[c-nsp] HSRp and OSPF metrics

[Ray Burkholder]

> 
> 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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