In one embodiment, an autonomous system border router (ASBR) advertises a same forwarding label for received advertised routes of a merging context that were advertised with a same forwarding label for the ASBR to use when sending corresponding packets. An ASBR receives via a routing protocol from a particular router in the same autonomous system, a plurality of same-labeled received routes advertised with a same first forwarding label within a merging context. In response to each of the plurality of same-labeled received routes having the same first forwarding label to use to forward packets to the particular router and being in the same merging context, the ASBR determines a merged forwarding label and advertises to a peer ASBR in another autonomous system (AS) each of the plurality of same-labeled received routes with the merged forwarding label for the peer ASBR to use to forward packets to the ASBR.