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ISIS routing update filter

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

3 REPLIES
Cisco Employee

Re: ISIS routing update filter

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.

Hall of Fame Super Silver

Re: ISIS routing update filter

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

Re: ISIS routing update filter

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

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