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Which address is used by the Unicast Reverse Path Forwarding protocol to validate a packet against the routing table?
A. source address
B. destination address
C. router interface
D. default gateway
Answer: A
Explanation:
The Unicast RPF feature helps to mitigate problems that are caused by the introduction of malformed or forged (spoofed) IP source addresses into a network by discarding IP packets that lack a verifiable IP source address. For example, a number of common types of denial-of-service (DoS) attacks, including Smurf and Tribal Flood Network (TFN), can take advantage of forged or rapidly changing source IP addresses to allow attackers to thwart efforts to locate or filter the attacks. For Internet service providers (ISPs) that provide public access, Unicast RPF deflects such attacks by forwarding only packets that have source addresses that are valid and consistent with the IP routing table. This action protects the network of the ISP, its customer, and the rest of the Internet.
http://www.cisco.com/en/US/docs/ios/12_2/security/configuration/guide/scfrpf.html
