Strict URPF cannot be applied to any customer that might be multihomed, which rules out any BGP customer or peer. The reason is that multi-homed networks are n

Strict URPF cannot be applied to any customer that might be multihomed, which rules out any BGP customer or peer. The reason is that multi-homed networks are not required to, and often do not advertise the same routes to all of their BGP peers. This may be done for routing policy purposes, traffic engineering, or simply to mitigate a temporary performance problem/outage with one of your transit providers/peers. This means that strict URPF has to be deployed on the many networks that are close to statically routed end users. However, even statically routed customers could be multihomed and send traffic asymmetrically. This is not common but could cause headaches for support - even if you make an exception it could get accidentally overridden in the future. On my networks (data center/hosting) we configure strict URPF on statically routed customers by default but not for BGP customers.