Cannot "overwrite" bgp no-export community

[Emmanouil Patiniotakis]

Hello,

I am working on an ISP and we have given the opportunity to our customers to send us a special BGP community when one of their host is under attack (blackhole community). We then match this community, we route it to null 0 and in addition we add a new community (without the additive keyword) and send it to our upstream provider so as to prevent malicious traffic from reaching our border router. Today a customer send us a prefix with the special community along with the community no-export. Although when we match the special community we overwrite all communities with the one given for our upstream blackhole procedure it seems that the no-export cannot be overwritten. As a result this prefix is not advertised to our upstream.

Is this expected? Well-known bgp sommunities such as no-export cannot be overwriten by a set statement without the additive word?

[Mark Pace Balzan]

Hi,

In xr as far as I know, we'll known communities will not be overwritten when you don't use additive.

to delete these you need to use the following:

  RP/0/RP0/CPU0:router(config-rpl)# delete community in (internet, no-export, no-advertise, local- as, *:*)

see http://www.cisco.com/c/en/us/td/docs/routers/crs/software/crs_r4-1/routing/command/reference/b_routing_cr41crs/b_routing_cr41crs_chapter_01000.html

Hope this helps

mark

[Emmanouil Patiniotakis]

Your answer is really helpful. Thank you very much.