[nsp] L1/2 ISIS Design

From: Pegg Damon (Damon.Pegg@carrier1.com)
Date: Wed May 09 2001 - 07:53:52 EDT


Hi. Tricky this one. I Have a nasty bug in 12.0.X code on my 72xx and GSR
Core in that the ISIS 'advertise' redistribution method doesn't work for
selective redistribution of L2 to L1. This is vital in an L1/2 topology
since IGP routes for iBGP next-hop addresses (ingress routers' loopback
addresses, typically) need to be redistributed into L1 in all L1 areas for:

Optimal routing to bgp next-hop, the majority of traffic on a carrier-class
network.

Injection of IGP metrics into exported MED values for effective and granular
multi-homed peering with an AS.

I have a little vague feedback that this function works if I turn on
wide-metrics in ISIS but has anyone experience of this? I can turn on
transition metric-style but how stable is it?

Hmmm...

Damon Pegg IP Backbone Engineer Carrier1 www.carrier1.net
"If you can look into the seeds of time, and say which grain will grow and
which will not, speak then to me."



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