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 01111001. To which interface will this datagram be forwarded using longest-prefix matching?

2. Suppose a datagram arrives at the router, with destination address 11101010. To which interface will this datagram be forwarded using longest-prefix matching?

3. Suppose a datagram arrives at the router, with destination address 00011010. To which interface will this datagram be forwarded using longest-prefix matching?

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Solution

1. Since the address is 01111001, it will go to interface 6.

2. Since the address is 11101010, it will go to interface 6.

3. Since the address is 00011010, it will go to interface 3.

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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 01111001. To which interface will this datagram be forwarded using longest-prefix matching?

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The answer was: 6

Question 2 of 3

Suppose a datagram arrives at the router, with destination address 11101010. To which interface will this datagram be forwarded using longest-prefix matching?

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The answer was: 3

Question 3 of 3

Suppose a datagram arrives at the router, with destination address 00011010. To which interface will this datagram be forwarded using longest-prefix matching?

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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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