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rakeshvelagala
Participant

BGP Sending Community Value

Hi All,

Just very simple config as below.

For the command "aggregate-address 153.153.153.0 255.255.255.0 attribute-map ATTR_SET", the network is loopback and is also  /24. I just want to send the community "no-export" using the aggregate command. When I check the sh ip bgp for this route, the community value is not shown. 

Instead of applying the ATTR_SET on the aggregate-command, if I use it on neighbor 10.1.1.1 route-map ATTR_SET, then I can see it is advertising the community value correctly. Can someone please advise what is wrong with the first way using aggregate?

r1(10.1.1.1) ----- (10.1.1.2)r2

R1#sh run | s router
router bgp 1
bgp log-neighbor-changes
neighbor 10.1.1.2 remote-as 2

R2#sh run | s router

router bgp 2
bgp log-neighbor-changes
network 153.153.153.0 mask 255.255.255.0
aggregate-address 153.153.153.0 255.255.255.0 attribute-map ATTR_SET
neighbor 10.1.1.1 remote-as 1

neighbor 10.1.1.1 send-community

R2#sh run int lo 1
Building configuration...

Current configuration : 69 bytes
!
interface Loopback1
ip address 153.153.153.153 255.255.255.0

R2#sh route-map

route-map ATTR_SET, permit, sequence 10
Match clauses:
Set clauses:
community no-export
Policy routing matches: 0 packets, 0 bytes

R1#sh ip bgp 153.153.153.0/24

BGP routing table entry for 153.153.153.0/24, version 4
Paths: (1 available, best #1, table default)
Not advertised to any peer
Refresh Epoch 1
2
10.1.1.2 from 10.1.1.2 (153.154.154.153)
Origin IGP, metric 0, localpref 100, valid, external, best
rx pathid: 0, tx pathid: 0x0

Thanks

10 REPLIES 10
Philip D'Ath
Advisor

This is a little outside my knowledge, but I believe the "no-export" community attribute is set in inbound routes (aka routes you are learning) - you don't set it outbound (aka routes you are sending to an external AS).

And the whole point of it is to prevent your AS sending routes learned from another AS outside of your own AS.

Sakthi Malli
Cisco Employee

Can you try remove/re-add "aggregate-address" statement or hard-reset BGP session to see if it helps

Thanks