Networking - Subnetting - Discussion

Discussion Forum : Subnetting - Subnetting (Q.No. 18)
18.
Which configuration command must be in effect to allow the use of 8 subnets if the Class C subnet mask is 255.255.255.224?
Router(config)#ip classless
Router(config)#no ip classful
Router(config)#ip unnumbered
Router(config)#ip subnet-zero
Answer: Option
Explanation:
A Class C subnet mask of 255.255.255.224 is 3 bits on and 5 bits off (11100000) and provides 8 subnets, each with 30 hosts. However, if the command ip subnet-zero is not used, then only 6 subnets would be available for use.
Discussion:
7 comments Page 1 of 1.

Zakura said:   5 years ago
What if ;ip classful?

HARDIK CHUGH said:   7 years ago
Because 1st is network address and last is a broadcast address which is not usable, hence 6 subnets.

Maria said:   8 years ago
How come 6 subnets?

Because if we are not including 0 means, totally 7 subnets only will come right? Kindly clarify it.

Dave said:   9 years ago
A mask of 224 in the last octet means the block size of each subnet is 32.

So the 1st subnet is 0 through 32, 64, 96, 128, 160, 192, 224 which gives 8 subnets.

But with "no ip subnet-zero" you can't use the "0" subnet so you get 7 subnets not 6.

Navin said:   10 years ago
255.255.255.224 already provides 8 subnets and 30 hosts each. Then, why there is need to use any other command.

The question and the answer also not clear ?
Where does 6 subnets come into this ?

Please justify !

Idris said:   1 decade ago
the first one is( Regardless of of class that is either class A,B or C). While the second one means you are not assigning IP to your router,

Third - have not come across that.

fourth - Assigning of ip without subnet masks Zero like 255.255.255.228 not 255.255.255.0.

Rohen said:   1 decade ago
What is the following command I don't know I have seen this 1st time please tell me?

Router(config)#ip classless
Router(config)#no ip classful
Router(config)#ip unnumbered
Router(config)#ip subnet-zero

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