pls look at diagram attached.
Router A and B are branch routers. B is PIM DR on the LAN becuase it has higher IP 10.36.200.3. There is only sparse-mode running and RP is WAN2 across the WAN links.
1. Normally, multicast tree is built from router B to WAN2(RP)
2. But if link B goes down, router B must build tree from B, A, WAN1, core-rtr1 then WAN2
3. however would this ever work? because when link B goes down, router B is one-armed with only interface F1/0 connected. But I was told interface F1/0 can't be incoming and outgoing interfaces at the same time. As a result, the tree can never be set up.
is it true?
3. if true, does it mean this design is flawed for multicast?
a backup link between router A and B via interface F1/1?
Thus router B can build tree via interface F1/1 which also becomes incoming int while F1/0 is outgoing interface