bgp local-as community string XRV

[sachin30720041]

Hello,

I have configured ebgp on 2 XRV routers. XRV13 is sending prefix with local-AS community string. XRV14 receives the prefix with community string set to 'local-AS'. According to my understanding, prefix should not leaving the local as.  Am I correct ?

XRV13------------XRV14

Below is the configuration.

XRV13
-------------------------
int gi0/0/0/0
ip address 100.130.140.13 255.255.255.0
no sh

int lo0
ip address 13.13.13.13 255.255.255.255

community-set comm1
local-as
exit

route-policy pol1
set community comm1
exit

route-policy pass
pass
exit

router bgp 13
address-family ipv4 unicast
network 13.13.13.13/32
exit
session-group session1
remote-as 14
exit
neighbor 100.130.140.14
use session-group session1
address-family ipv4 unicast
send-community-ebgp
route-policy pass in
route-policy pol1 out
exit

XRV14
-------------------------
int gi0/0/0/0
ip address 100.130.140.14 255.255.255.0
no sh

int lo0
ip address 14.14.14.14 255.255.255.255

route-policy pass
pass
exit

router bgp 14
address-family ipv4 unicast
exit
session-group session1
remote-as 13
exit
neighbor 100.130.140.13
use session-group session1
address-family ipv4 unicast
send-community-ebgp
route-policy pass in
route-policy pass out
exit

ON XRV14

RP/0/0/CPU0:XRV14#show bgp ipv4 unicast 13.13.13.13
Last Modified: Aug 20 18:48:42.952 for 00:00:01
Paths: (1 available, best #1, not advertised outside local AS)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
13
100.130.140.13 from 100.130.140.13 (13.13.13.13)
Origin IGP, metric 0, localpref 100, valid, external, best, group-best
Received Path ID 0, Local Path ID 0, version 6
Community: local-AS
Origin-AS validity: not-found

Thanks,

Sachin

[Harold Ritter · Accepted solution]

Hi @sachin30720041 ,

This is normal behaviour as the local-as community is attached to the prefix once the decision has been made to advertise it to ASN 14, so it is too late to filter it out based on the local-as community. If you want the local-as to take effect, you need to attach it to the prefix when you originate it locally as follow:

router bgp 13
address-family ipv4 unicast
network 13.13.13.13/32 route-policy pol1
exit

Regards,

[MHM Cisco World]

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