@Joshua Schroth
it's not supported, due to the way BFD works, it's not suitable to work with some crypto configurations because the packet goes from the interface to the neighbor, arrives in the physical interface, it's processed and sent back without going through the whole interface process sequence, then it's not injected into tunneling process to reply, anyway, it's supported with GRE and DMVPN for some platforms.
BFD is not supported on VTI tunnel.
CCIE 52804
