The network administrator of a branch office network has decided to deploy Unicast RPF at the access layer. He insists that the design must guarantee that all the packets arriving on the router…

In strict mode, the router performs a reverse-path lookup and drops the packet if the best return path for the source address is not the same interface that received the packet. At the access layer with single-homed, symmetrically routed hosts, this guarantees that every source address maps to the interface subnet, fulfilling the administrator's requirement without false positives from asymmetric routing.

uRPF loose mode only checks that the source address appears anywhere in the routing table, so it does not enforce that the address belongs to the receiving interface's subnet.

uRPF VRF mode is used to perform the reverse-path check within a specific VRF context and does not inherently enforce per-interface subnet assignment.

RPF feasible mode (also called feasible-path or loose with allow-default) accepts packets as long as the source is reachable via any feasible path, which does not guarantee subnet-to-interface alignment.