[c-nsp] IS-IS Multiarea on 12.2 SR

Oliver Boehmer (oboehmer) oboehmer at cisco.com
Fri Nov 6 04:54:39 EST 2009


Mikael,

> > to have only the default-route in the RIB. Not sure if this helps,
not
> > sure which problem you are trying to solve :)
> 
> This is probably the biggest problem, the few people doing L1-L2
> separation are those into academia/theoretics (passing a test/exam),
when
> you go into the real world it's no longer in major use.
>
> I've never bothered to learn about ISIS L1, never needed to, see no
use
> for it in real life. L2-only is the way to go.

Well, there are L1L2 networks in production, and when you think about
scaling Layer 3 into the (MetroE) access layer, you start to deal with
>10000 of routers in an ISIS domain, something which can't be handled in
a single area. 
 
> I'd also recommend against it from a sw standpoint. Sure, the sw
supports
> it, but it hasn't been exposed to real life as much as L2 only because
of
> above reasons.

see above, L1L2 is deployed, I personally know of two carriers'
networks. So there is definitly exposure...

	oli


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