ISIS routing update filter

devang_etcom · ‎05-10-2009

Hello,

How to filter the specific prefixes from IS-IS routing update sending to all neighbor or specific neighbor? for flat ISIS or multi level ISIS design!

regards

Devang Patel

Laurent Aubert · ‎05-11-2009

Hi,

If the prefix is part of ISIS domain, you can apply the no isis advertise-prefix on the interface:

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_is1.html#wp1012705

If you are redistributing this prefix from another routing protocol then you have the classic route-map you can attach to your redistribution statement.

One thing you can't do is to filter for a specific neighbor. ISIS is a link-state protocol so every routers must have the same topology view.

HTH

Laurent.

Giuseppe Larosa · ‎05-12-2009

Hello Devang,

being IS-IS link state there are limited actions that are possible.

You can hide the details of some specific routes using the following:

build a L2 IS-IS adjacency (different nets on R1 and R2)

declare the interfaces that are associated to the subnets you want to hide as level-1 only.

the default both for the process and for the links is to be L2/L1.

With a setup like this R2 doesn't learn the details of a L1-only prefix on the direct link with R1.

This can lead to R2 learning the prefix from another path.

This happens because interfaces L1-only will be missing from the L2 LSP built by R1 and passed to R2 on the L2 only direct link.

Hope to help

Giuseppe

devang_etcom · ‎05-13-2009

Guys,

Thanks for your reply! finally no any way to achieve the routing update filter in ISIS. We can filter adj but not updates.

thanks,

Devang Patel