[c-nsp] HSRp and OSPF metrics

[Bruce Pinsky]

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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

- --
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bep

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