Re: bgp route advertisment , particularly aggregate/summary to

On 03/10/2012 09:10 PM, Aaron wrote:
> Thanks Jochen, It wasn't in the bgp...the (3) subordinate 172's/24 were in
> the igp... so with that, I could have used a network statement in bgp and
> got them inserted that way, then used the aggregate which would have then
> acted upon them. But how would I have directed that aggreagate at only one
> of my igbp neighbors and not all of them ?
>

That could be accomplished by just filtering the aggregate from
advertisements to the other neighbors using a distribute-list,
prefix-list or a route-map.

neighbor w.x.y.z distribute-list ACL_FOO out
neighbor w.x.y.z prefix-list PL_FOO out
neighbor w.x.y.z route-map RM_FOO out

My personal favorite are route-maps.

ip prefix-list PL_NET_172 permit 172.0.0.0/8
!
route-map RM_BGP_POLICY->R6 deny 10
 match ip address prefix-list PL_NET_172
route-map RM_BGP_POLICY->R6 permit 1000
!
router bgp 666
 network 172.16.1.0 mask 255.255.255.0
 aggregate-address 172.0.0.0 255.0.0.0 summary-only
 neighbor 150.21.6.6 remote-as 666
 neighbor 150.21.6.6 update-source lo0
 neighbor 150.21.6.6 route-map RM_BGP_POLICY->R6 out

Another possibility would be to add a community value to the aggregate
when it is originated. After that you can filter routes carrying that
community from BGP updates to specific neighbors.

route-map RM_BGP_AGGREGATE permit 10
 set community 666:1
!
ip community-list standard CL_IBGP_FILTER permit 666:1
!
ip bgp new-format
!
route-map RM_BGP_POLICY->R6 deny 10
 match community CL_IBGP_FILTER
route-map RM_BGP_POLICY->R6 permit 1000
!
router bgp 666
 network 172.16.1.0 mask 255.255.255.0
 aggregate-address 172.0.0.0 255.0.0.0 summary-only route-map
RM_BGP_AGGREGATE
 neighbor 150.21.6.6 remote-as 666
 neighbor 150.21.6.6 update-source lo0
 neighbor 150.21.6.6 route-map RM_BGP_POLICY->R6 out

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Received on Sat Mar 10 2012 - 21:53:53 ART