Extended communities

[debottym2]

  Is there was a way to search on a route reflector and find all prefixes that were tagged with a certain community?

I am finding it a little tedeious to check each prefix with "sho ip bgp vpnv4 all x.x.x.x" and find the extended communities.

[Peter Paluch]

Hello,

There are two commands available:

show ip bgp vpnv4 all community-list ...

show ip bgp vpnv4 all extcommunity-list ...

Would they perhaps be useful for you? They accept a corresponding community ACL as an argument, and should result in displaying only those prefixes that are permitted by these ACLs (i.e. tagged with corresponding communities).

Best regards,

Peter

[debottym2]

Hello Peter,

Thanks for the prompt response. Unfortunately, those didn't return any results.  I am adding the necessary snippets of the router config. and output that I am looking for.

Regards,

Router config (IP addresses and communities have been changed and aren't accurate)

address-family vpnv4

neighbor  4.4.4.4 route-map OptionBTestIn in

neighbor  4.4.4.4 route-map OptionBTestOut out

!

route-map OptionBTestIn deny 10

match extcommunity 1

!

!

ip extcommunity-list 1 permit rt  911:1

ip extcommunity-list 101 permit RT:911:.+

!

NYCMNYBXH71MG01#sho ip bgp vpnv4 all 9.9.9.9/30        

    4.4.4.4 from 4.4.4.4

      Origin IGP, metric 5326, localpref 100, valid, external

     Extended Community: RT:911:526 RT:911:1202 (output I am lookin for)

      mpls labels in/out nolabel/709595

NYCMNYBXH71MG01#          

NYCMNYBXH71MG01#

To summarize, I am looking for all prefixes that are received from 4.4.4.4 and tagged with 911:526 (don't care about the rest of the communities)

Hope that helps.

[Peter Paluch · Accepted solution]

Hello,

I apologize for replying lately - I am truly sorry.

According to the Command Reference at

http://www.cisco.com/en/US/docs/ios-xml/ios/iproute_bgp/command/bgp-c1.html#wp3653605863

to match the route-target extended community, we should be using standard extcomm list instead of expanded extcomm list. So instead of the extcommunity-list 101 you have now, try using:

ip extcommunity-list 2 permit rt 911:526

I have tried looking into ways of using the expanded extcomm list to match extended communities of a specific type only. Sadly, as far as I could find out, there is no way to match on the type of the extended community (i.e. SoO, RT, etc.) in an expanded extcomm list. At least I was not able to find out a way to do it. That is the reason why the "RT:" prefix in your existing expanded extcomm list is not evaluated properly and as a result, nothing is displayed.

Best regards,

Peter

[debottym2]

Peter,

No apologies necessary, I am very grateful for your help thus far.

I think the direction you have given me above was exactly what I needed. The subtle difference between using a Standard and Expanded extendcomm list was HUGE.

Thank you so much and wish you a wonderful 2013 and beyond!

Regards,

Deb