Which property defines the outgoing interface in a NAT rule for masquerading?

• A. in-interface
• B. out-interface
• C. src-address
• D. dst-address

Answer: (B)

Masquerading works by changing the source address of packets as they leave your network, so the rule must be tied to the path those packets take to the Internet. The property that links a NAT rule to the path the traffic exits through is the outgoing interface. By specifying the interface the traffic goes out on, the router knows which traffic to translate and on which egress path replies should return. The other properties describe where the packet came from or where it’s going, or the interface it arrived on, but they don’t define the exit path. So, the outgoing interface is the element that determines which traffic gets masqueraded.