A distributed-forwarding router platform contains a master and a standby route processing manager (RPM). The master RPM uses dynamic internal routing codes to facilitate the replication of multicast packets within the router. As internal routing codes are assigned, the assignments are shared with the standby RPM. Should the standby RPM have to take over as the master RPM, the new master consults the internal routing codes assigned by the previous master as the new master builds multicast state, insuring that the internal routing codes the new master assigns are consistent with those used by the prior master. This allows the multicast forwarding plane to remain available during RPM failover, without a shutdown or unstable period while the new master RPM propagates internal routing codes. Other embodiments are also described and claimed.