[c-nsp] BGP blackhole community config

Oliver Boehmer (oboehmer) oboehmer at cisco.com
Tue Jun 21 02:55:15 EDT 2016


On 20/Jun/16 19:41, Jared Mauch wrote:

>> Tags are specific to Cisco, you should be using a community instead.

>We use tags on Juniper quite successfully. Makes it easy to introduce
>static routes into iBGP.

>It irks me that Cisco does not support this.

> You can use something like redistribute static against a route-map that matches the tag and marks your (local) discard community.

>Won't work.

>You can't have a tag as a match condition in Cisco. It will throw up an
>error that the OP shared earlier.

this is not entirely correct: 

BGP routes don’t have a tag in Cisco’s implementation, so you can’t match against a tag when a route-map controls BGP path advertisements. You can use it when redistributing other route sources which do support tags (statics, etc.) into BGP:

r1(config)#route-map FOO
r1(config-route-map)#match tag 123

this one works:

r1(config)#router bgp 65001
r1(config-router)#redistribute static route-map FOO

this one doesn’t

r1(config-router)#neighbor remote-as 65002
r1(config-router)#neighbor route-map FOO out
% "FOO" used as BGP outbound route-map, tag match not supported
% not supported match will behave as route-map with no match

More information about the cisco-nsp mailing list