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 01110111. To which interface will this datagram be forwarded using longest-prefix matching?

2. Suppose a datagram arrives at the router, with destination address 01111010. To which interface will this datagram be forwarded using longest-prefix matching?

3. Suppose a datagram arrives at the router, with destination address 01100110. To which interface will this datagram be forwarded using longest-prefix matching?

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Solution

1. Since the address is 01110111, it will go to interface 4.

2. Since the address is 01111010, it will go to interface 4.

3. Since the address is 01100110, it will go to interface 4.

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That's incorrect

That's correct

The answer was: 4

Question 1 of 3

Suppose a datagram arrives at the router, with destination address 01110111. To which interface will this datagram be forwarded using longest-prefix matching?

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The answer was: 4

Question 2 of 3

Suppose a datagram arrives at the router, with destination address 01111010. To which interface will this datagram be forwarded using longest-prefix matching?

Check Hint skip

The answer was: 4

Question 3 of 3

Suppose a datagram arrives at the router, with destination address 01100110. 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