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An IP router implementing Classless Inter-domain Routing (CIDR) receives a packet with address 131.23.151.76. The router’s routing table has the following entries :
The identifier of the output interface on which this packet will be forwarded is ______.
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- 0
- 1
- 2
- 4
Correct Option: B
Address 131.23.151.76
Coming to I field of given routing table.
⇒ 131.16.0.0/12
131.0001 0111.151.76
131.0001 0000.0.0 (mask bit = 12)
131.16.0.0 (matched)
Coming to II field of given routing table.
⇒ 131.28.0.0/14
131.0001 0111.151.76
131.0001 0100.0.0 (mask bit = 14)
131.20.0.0 (not matched)
Coming to III field of given routing table
⇒ 131.19.0.0/16
131.0001 0111.151.76
131.0001 0111.0.0 (mask bit = 16)
131.23.0.0 (not matched)
Coming to IV field of given routing table
⇒ 131.22.0.0/15
131.0001 0111.151.76
131.0001 0110.0.0 (mask bit = 15)
131.22.0.0 (matched)
∵ I and IV entries are matched, we pickup longest mask bit
∴ Output interface identifies is 1.
