[c-nsp] vs isis routing levels

[Saku Ytti]

On (2013-12-20 18:14 +0100), Patrick M. Hausen wrote:

> Am 20.12.2013 um 14:58 schrieb Arne Larsen / Region Nordjylland <arla at rn.dk>:
> > We are planning to resign our enterprise environment.
> > It's based on Cisco boxes running isis level1-2 routes
> > Would you keep this or would you make all level-2 routes.
> 
> If your network is small enough to call for a single area, go all level-2.

I think this is backwards. If it's small enough to be single area, it does not
matter what it is.
If maybe sometime in future you might need more areas, make your network
level-2, i.e. core, to which you can attach say metro areas.

level-2 is always correct answer when you start ISIS network, because you
don't lose anything, and you gain ability to add areas later on, if you need
to.

We're right now rocking about 1500 nodes flat l2 core. But we are in situation
where we're going to replace L2/LAN metro networks with MPLS, and this is good
situation to look into our alternatives

a) keep flat L2
b) make each metro L1, and metro<->core border routers L1L2
c) make metro L2 and core L2, but don't connect IGP domains. Capitalize BGP-LS
and Segment Routing for end-to-end MPLS with MPLS-TE capabilities, without
combining IGP.

-- 
  ++ytti