Here we go - Question of the day #1

rakem

Since I'm studying BGP right now here is my question of the day:

If I have the following config on R2:

router bgp 100
 no synchronization
 bgp log-neighbor-changes
 neighbor 10.1.1.1 remote-as 100
 neighbor 10.1.1.1 send-community
 neighbor 5.5.5.5 remote-as 54
 neighbor 5.5.5.5 route-map no-export in

ip prefix-list 112 seq 5 permit 112.0.0.0/8

route-map no-export permit 10
 match ip address prefix-list 112
 set community no-export

and this on another router:

router bgp 100
 no synchronization
 bgp log-neighbor-changes
 aggregate-address 112.0.0.0 248.0.0.0 as-set summary-only
 neighbor 10.1.1.2 remote-as 100
 neighbor 1.2.3.4 remote-as 50

Will the aggregate range be advertised to the EBGP neighbor 1.2.3.4?
(Assume there are matching prefixes in the 112.0.0.0/5 range and that all other routing is working)

If yes - why
If no - why and how to fix?

NetworkVeteran

Will the aggregate range be advertised to the EBGP neighbor 1.2.3.4?

No.

(Assume there are matching prefixes in the 112.0.0.0/5 range and that all other routing is working)

If no - why and how to fix?

The aggregate by default inherits the 'no-export' community from the more specific 112.0.0.0/8. To change this behavior, use the attribute-map option.

rakem

Exactly!
Aggregate routes will carry attributes from the individual prefixes that have been aggregated when you use as-set