Refer to the exhibit. A network administrator has been asked to summarize the networks shown in the exhibit as part of a multiarea OSPF implementation. All addresses are using a subnet mask of 255.255.255.0. What is the correct summarization for these eight networks?

IT Questions Bank › Refer to the exhibit. A network administrator has been asked to summarize the networks shown in the exhibit as part of a multiarea OSPF implementation. All addresses are using a subnet mask of 255.255.255.0. What is the correct summarization for these eight networks?

10.0.4.0 255.255.0.0
10.0.0.0 255.255.240.0
10.0.4.0 255.255.248.0
10.0.8.0 255.255.248.0

Explanation: The only correct summarization is 10.0.0.0 255.255.240.0. The binary calculation would be:
10.0.4.0 00001010.00000000.0000 0100.00000000
10.0.5.0 00001010.00000000.0000 0101.00000000
10.0.6.0 00001010.00000000.0000 0110.00000000
10.0.7.0 00001010.00000000.0000 0111.00000000
10.0.8.0 00001010.00000000.0000 1000.00000000
10.0.9.0 00001010.00000000.0000 1001.00000000
10.0.10.0 00001010.00000000.0000 1010.00000000
10.0.11.0 00001010.00000000.0000 1011.00000000
Determining the matching bits and then adding zeroes at the end results in a summary network address of 10.0.0.0; since 20 bits match, the mask would be /20.

Exam with this question: CCNA 3 (v5.0.3 + v6.0) Chapter 9 Exam Answers