JunOS tagging aggregate route from more specific route - bgp communities

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Asked 2 months ago

Modified 2 months ago

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I have a certain use case with rtbh for the following:

A /32 route (say 10.1.1.1/32) is injected into the network with a specific bgp community
I'd like to match the aggregate prefix that /32 belongs to (say 10.1.1.0/24) and attach the "no_advertise" community to it or simply stop advertising it to our peer.

Is this even possible on junos or ios-xr? I've been trying to figure it out with policy statements in either case but to no avail.

If possible, if someone can provide config snippet examples, it'd be very helpful.

Thank you

asked Sep 29 at 15:45

Network Samurai

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I've had a mess around in the lab and I don't think this is possible. I'm not sure you can take a prefix with a community string and then match it against a larger aggregate - even with Junos policy subroutines, taking the output of the RTBH "subroutine" and matching against a "shorter" prefix doesn't seem possible. Is there a reason you want to blackhole the aggregate? Normally you would let the customer announce any length prefix to you (provided it's from their range) with the RTBH community attached and you would simply re-advertise that to all your nodes and discard that traffic.
– Benjamin Dale
Oct 4 at 22:12

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