A router receives a message addressed 172161575 The relevant

A router receives a message addressed 172.16.15.75. The relevant routing table entries are 172.16.0.0 /20 – Serial 0, 172.16.0.0 /23 – Ethernet 0, and 172.16.15.64 /26 – Ethernet 1. Which interface will the router forward the packet to?

A. Serial 0.

B. Serial 1.

C. Ethernet 0.

D. Ethernet 1.

E. None of the above. The packet will be dropped.

Solution

D is correct. If you translate 172.16.15.75 into binary, it matches 26 bits in the last routing table entry, as opposed to only 20 in the first two.

A, B, C, and E are incorrect. A and C are incorrect because the address bits match more of the last route entry; it will be chosen over the other two. B is incorrect because there is no route for Serial 1. E is incorrect because the packet will not be dropped because there is a routing table entry for it.