[j-nsp] ISIS L1 and L2 adjacency

Mark Tinka mark.tinka at seacom.mu
Thu Jul 27 08:46:25 EDT 2017

On 18/Jul/17 14:20, Saku Ytti wrote:

> To OP. I hope this is to brush up towards exam or something. I don't
> think there is use case for areas in ISIS or multi-level ISIS. If you
> need scale, have separate L2 segments, combine them with BGP for
> seamless MPLS.


When I first deployed IS-IS, I used my OSPF tendencies and deployed L1
within PoP's, and L2 between PoP's. Once I figured out that Route
Leaking between levels for all /32 + /128 IP addresses was necessary, it
made the case for just a single L2 IS-IS domain.

IS-IS scales very well (probably just as good as OSPFv3). And besides,
routers are way faster now than when Link State IGP's first hit the scene.


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