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?
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.
Sechonge said:
9 years 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
Subnet 11111000 Adding
-------------
01000000 = 64.
Therefore n/w id: 172.16.64.0.
66: 01000010
Subnet 11111000 Adding
-------------
01000000 = 64.
Therefore n/w id: 172.16.64.0.
Munna said:
9 years 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
Subnet 11111000 Adding
-------------
01000000 = 64.
Therefore n/w id: 172.16.64.0.
Here 5 bits are used for subnetting from the third octet.
66: 01000010
Subnet 11111000 Adding
-------------
01000000 = 64.
Therefore n/w id: 172.16.64.0.
Ehsan Faghih said:
9 years ago
Consider it we have 1 bit for subnet. Then how many of sub-network we could have? answer:2.
Why: because one bit only can determine 2 states (ways) for us! (0 or 1).
In this case, when we determine the subnet mask we found that we have 5bits for subnets.
Now tell me " how many states provide for us by 5bits? 32 or 64?
YES! 64 states is true answer!
Then we will have 64 sub-network by 5bits subnets.
Why: because one bit only can determine 2 states (ways) for us! (0 or 1).
In this case, when we determine the subnet mask we found that we have 5bits for subnets.
Now tell me " how many states provide for us by 5bits? 32 or 64?
YES! 64 states is true answer!
Then we will have 64 sub-network by 5bits subnets.
Joshua said:
5 years ago
And why not 48, i.e option B.
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