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What is uRPF checking first when the packet enters the interface?
A. Route available in FIB It verifies a reverse patch via the fib to the source
B. It check the egress access list
C. It check the ingress access list
D. Other
Correct Answer: A
Explanation/Reference:
When Unicast RPF is enabled on an interface, the router examines all packets received as input on that interface to make sure that the source address and source interface appear in the routing table and match the interface on which the packet was received. This “look backwards” ability is available only when Cisco express forwarding (CEF) is enabled on the router, because the lookup relies on the presence of the Forwarding Information Base (FIB).
CEF generates the FIB as part of its operation.
Answer C.