Here is one reason for some to care :
If you want to do interdomain multicast, and your address space is not announced globally (say because you have a /24 that is not from the swamp), you are likely to be black-holed due to RPF failures (as your unicast and multicast routing is likely to be different).
This has caused problems from time to time...
Regards Marshall Eubanks
Until such time as vendor C determines that RPF lookups should use the MRIB first, then the URIB, rather than the final RIB, the following will help: router bgp distance mbgp 19 19 19 ip mroute 0.0.0.0 0.0.0.0 bgp Null0 20 or if using 12.1: router bgp address-family ipv4 multicast distance bgp 19 19 19 ip mroute 0.0.0.0 0.0.0.0 bgp Null0 20 not having looked at vendor J's multicast, I can't speak to it. This does, however, make absolutely certain that only MBGP routes determine RPF choices. If you expect or desire unicast routes to drive multicast routing decisions, the above is not for you. I had to do this to get around a bunch of RPF hedge cases.