R2 should aggregate all the networks in 3 . 1 .0.0 address space and advertise a single
aggregate route that only aggregates the specific routes for subnets under the 3 .0.0.0
network in it's BGP table, ensure that the atomic-aggregate attribute is not attached to the
aggregate route. This aggregation should be configured such that R 1 in AS 1 00 is the
only AS that receives the aggregate route, R3 or future peer neighbors should NOT
receive the aggregate route. R 1 should use R2 as the next hop to reach any of the specific
routes within the aggregate, R I should NOT use R2 if it' s network 3 . 1 . 1 1 .0 124 network
is down. R3 does NOT need NLRI to network 3 . 1 . 1 1 .0 124 advertised by R 1 .
deth1k wrote: »
Create a summary/aggregate route, create a prefix list which would only allow that route to propagate, use that same prefix list in the neighbor statement outbound to R3, this will filter all other subnets (if summary-only is not used).
You can then filter this agregate on other routers or towards other AS'es.
burbankmarc wrote: »
The lab makes it seem like you should be able to do all of this within the aggregate-address command, all though I may be off base on that one.
Forsaken_GA wrote: »
The best way I can think to do this would be to use a route-map to set the no-export community as part of the aggregate-address command, that should keep it from leaving the AS. And then just have a route-map pointing to that one particular neighbor to remove the no-export community, allowing it to be propagated out.