Interactive Problems, Computer Networking: A Top Down Approach

Longest Prefix Matching

Consider a datagram network using 8-bit host addresses.
Suppose a router uses longest-prefix matching, and has the following forwarding table:

Question List

1. Suppose a datagram arrives at the router, with destination address 11111101. To which interface will this datagram be forwarded using longest-prefix matching?

2. Suppose a datagram arrives at the router, with destination address 11111010. To which interface will this datagram be forwarded using longest-prefix matching?

3. Suppose a datagram arrives at the router, with destination address 00111101. To which interface will this datagram be forwarded using longest-prefix matching?

Solution

1. Since the address is 11111101, it will go to interface 3.

2. Since the address is 11111010, it will go to interface 3.

3. Since the address is 00111101, it will go to interface 4.

That's incorrect

That's correct

The answer was: 3

Question 1 of 3

Suppose a datagram arrives at the router, with destination address 11111101. To which interface will this datagram be forwarded using longest-prefix matching?

The answer was: 3

Question 2 of 3

Suppose a datagram arrives at the router, with destination address 11111010. To which interface will this datagram be forwarded using longest-prefix matching?

The answer was: 4

Question 3 of 3

Suppose a datagram arrives at the router, with destination address 00111101. To which interface will this datagram be forwarded using longest-prefix matching?