We want to implement Multi-Router APS with MLPPP solution, but i am not sure if there is any restriction on the member IP addresses we can use for PGP and ICRM. For PGP udp sessions, documentation suggests we can use loopback addresses, but only gives example using a dedicated interlink. For the ICRM session (needed for stateful MLPPP), there is no indication if loopback addresses can be used and documentation examples suggest to use a dedicated link between the routers. The problem with using dedicated links is that if the link fails, both routers go active on APS possibly leading to outage. To avoid this scenario, we want to guarantee that ICRM and PGP sessions are never lost unless one of the routers is completely shutdown, so we plan to use loopback addresses as member ip instead of dedicated link and put two interlinks between ASR903 for redundancy. OSPF is used to share IP routes.
Aside of this, i have a couple of other questions:
-is there only needed one ICRM group between the routers? Or we must create one independent ICRM group for each SONET controller?
-If we don't use BFD monitor on ICRM session, documentation states it detectes failure based on "route-watch". If I understood correctly, the ICRM session will be bring down immediatly if there is no possible route to the member IP (i mean, not even a default route). Is that right?
documentation reference: http://www.cisco.com/c/en/us/td/docs/ios/wan/configuration/guide/15_1s/wan_15_1s_book/wan_mlppp_mr_aps.html
diagram:
