Question

An SP engineer on an IOS XR ASBR must advertise a single summary prefix 203.0.113.0/22 to an eBGP peer instead of the four contributing /24 routes currently in the BGP table. However, the more-specific 203.0.113.0/24 must still be advertised to the same peer for a downstream customer failover requirement, while the other three /24s remain hidden. Which configuration approach achieves this?

Accepted Answer

Configure the aggregate with a suppress-map (or route-policy) that matches only the three /24s to be suppressed, allowing 203.0.113.0/24 to still be advertised alongside the summary.

Answer

Use 'aggregate-address 203.0.113.0/22 summary-only' — this automatically leaks the first contributing prefix while suppressing the rest.

Answer

Apply 'aggregate-address 203.0.113.0/22 as-set' so the aggregate and all four specifics are advertised with a merged AS_PATH.

Answer

Use an outbound route-policy with 'prefix-set' permitting 203.0.113.0/22 and 203.0.113.0/24 only, without any aggregate-address statement.