Networking - Subnetting - Discussion

Discussion Forum : Subnetting - Subnetting (Q.No. 9)
9.
What is the subnetwork number of a host with an IP address of 172.16.66.0/21?
172.16.36.0
172.16.48.0
172.16.64.0
172.16.0.0
Answer: Option
Explanation:
A /21 is 255.255.248.0, which means we have a block size of 8 in the third octet, so we just count by 8 until we reach 66. The subnet in this question is 64.0. The next subnet is 72.0, so the broadcast address of the 64 subnet is 71.255.
Discussion:
14 comments Page 2 of 2.

Stranger said:   10 years ago
How next subnet be 72?

Stranger said:   10 years ago
Who next subnet be 72? If we increased by 8.

Abhijeet said:   1 decade ago
That 66 came from where?

Racharla Chandra Kanth said:   1 decade ago
There are 21 N/w bits and the given IP is a Class B IP so by default 16 bits are for n/w. Here 5 bits are used for subnetting from the third octet.

66: 01000010
Subbnet 11111000 Anding
-------------
01000000 = 64.

Therefore n/w id: 172.16.64.0.


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