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 00100100. To which interface will this datagram be forwarded using longest-prefix matching?

2. Suppose a datagram arrives at the router, with destination address 01010101. To which interface will this datagram be forwarded using longest-prefix matching?

3. Suppose a datagram arrives at the router, with destination address 10111011. To which interface will this datagram be forwarded using longest-prefix matching?

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Solution

1. Since the address is 00100100, it will go to interface 6.

2. Since the address is 01010101, it will go to interface 2.

3. Since the address is 10111011, it will go to interface 1.

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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 00100100. To which interface will this datagram be forwarded using longest-prefix matching?

Check Hint skip

The answer was: 2

Question 2 of 3

Suppose a datagram arrives at the router, with destination address 01010101. To which interface will this datagram be forwarded using longest-prefix matching?

Check Hint skip

The answer was: 1

Question 3 of 3

Suppose a datagram arrives at the router, with destination address 10111011. 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