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SUPPOSE WE ARE GIVEN TWO BITS FOR SUBNET THEN WHICH ONE WILL BE THE THIRD SUBNET 10 OR 11

+1 vote

## if you have 2 bit then there are 4 posiblities.

00--- subnet id

01--- first subnet

10---2nd subnet

11---3rd subnet

Example:

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in one of the question of ace test series they asked the fourth octet of last ip address of the 3rd subnet for a class c network with subnet mask /26..

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@abhisheskmehta when we do subnetting we assume  that for 2 bit(2^2-2=2 subnets) subnetting that 00 goes for 0th subnet and 01 (first subnet ) 10 (second subnet) and last one 11(DBA subnet) (we assume that network itself will not participate in subnetting).So how can u say that 11 is third subnet?If we assume that network can participate in subnetting then 2^2=4 subnets and 00(first subnet) 01(second subnet) 10(third subnet) 11(4th subnet).correct me if i am wrong.
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Its little bit ambiguous . But In gate question it is given first id is subnet id or total number of subnet = 2^n -2 .
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so as of now there will not be third subnet  for the given question because we follow the assumption that number of subnets=2^n-2 so only first and second subnets are possible.correct me if i am wrong.
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what if  the network has suppose 200 ip and we divide it as

1st subnet :- 100 ip

2nd subnet :- 50 ip

3rd subnet :- 50 ip.

Then we can divide the network into 3 subnets.
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@sabir this can be done using 2 bits with  the help of  variable length subnetting.two choices might be there, subnetting bit as 1 for first subnet and 00 for second subnet and 01 for third subnet or 0 for first subnet and 10 for second subnet and 11 for third subnet.thisquestion is different from the given question.

It depends upon the way in which you want to divide the network into subnets.

Eg:- 200.254.254.0/26 is a class C network having 2 bits for subnet ID.

NOTE:- /26 is CIDR value which means number of 1s in the subnet mask.

In this the first 2 bits of last octet are for subnet i.e. 200.254.254.00000000.

Now if you want to divide this network into two equal subnets then we need only the 1st bit of subnet bit and it would be divided as

200.254.254.0/25 to 200.254.254.127/25 -----> subnet 1--------> 200.254. 254 .00000000/25 to 200.254. 254 .01111111/25.

200.254.254.128/25 to 200.254.254.255/25 ---------> subnet 2------> 200.254. 254 .10000000/25 to 200.254. 254 .11111111/25.

if you want to divide subnet 1 into two equal subnets then we need  the 1st and 2nd bit of subnet bit and it would be divided as

200.254.254.0/26 to 200.254.254.63/26 -----> subnet 3--------> 200.254.254.00000000/26 to 200.254.254.00111111/26.

200.254.254.64/26 to 200.254.254.127/26 -----> subnet 4--------> 200.254.254.01000000/26 to 200.254.254.01111111/26.

Similarly, if you want to divide subnet 2 into two equal subnets then we need  the 1st and 2nd bit of subnet bit and it would be divided as

200.254.254.128/26 to 200.254.254.191/26 -----> subnet 5--------> 200.254.0.10000000/26 to 200.254.254.10111111/26.

200.254.254.192/26 to 200.254.254.255/26 -----> subnet 6--------> 200.254.254.11000000/26 to 200.254.254.11111111/26.

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