Interactive end-of-chapter exercises

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:

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Question List

1. Suppose a datagram arrives at the router, with destination address 01111101. To which interface will this datagram be forwarded using longest-prefix matching?

2. Suppose a datagram arrives at the router, with destination address 01111110. To which interface will this datagram be forwarded using longest-prefix matching?

3. Suppose a datagram arrives at the router, with destination address 10100000. To which interface will this datagram be forwarded using longest-prefix matching?

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Solution

1. Since the address is 01111101, it will go to interface 6.

2. Since the address is 01111110, it will go to interface 6.

3. Since the address is 10100000, it will go to interface 6.

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That's incorrect

That's correct

The answer was: 6

Question 1 of 3

Suppose a datagram arrives at the router, with destination address 01111101. To which interface will this datagram be forwarded using longest-prefix matching?

Check Hint skip

The answer was: 6

Question 2 of 3

Suppose a datagram arrives at the router, with destination address 01111110. To which interface will this datagram be forwarded using longest-prefix matching?

Check Hint skip

The answer was: 6

Question 3 of 3

Suppose a datagram arrives at the router, with destination address 10100000. To which interface will this datagram be forwarded using longest-prefix matching?

Check Hint skip

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We greatly appreciate the work of John Broderick (UMass '21) in helping to develop these interactive problems.

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Comments welcome and appreciated: kurose@cs.umass.edu