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Beginner

Extended communities

  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.

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Hall of Fame Cisco Employee

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

View solution in original post

4 REPLIES 4
Highlighted
Hall of Fame Cisco Employee

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

Highlighted

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.

Highlighted
Hall of Fame Cisco Employee

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

View solution in original post

Highlighted

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

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