GATE CSE 2007 | Question: 67, ISRO2016-72

Question

The address of a class $\text{B}$ host is to be split into subnets with a $6\;\text{-bit}$ subnet number. What is the maximum number of subnets and the maximum number of hosts in each subnet?

• A. $62$ subnets and $262142$ hosts.

• B. $64$ subnets and $262142$ hosts.

• C. $62$ subnets and $1022$ hosts.

• D. $64$ subnets and $1024$ hosts.

Comments

at any cost the no of subnets will not be 62 they should be 64 and the no of hosts can be made 2^n in present routers of cisco  i have read it some where so  64 ,1024  can be right

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Similar question: https://gateoverflow.in/480/gate2008-57

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Suppose a class B network: 128.16.0.0 Now if we make $2^6$ subnets first one will be:

$1000000.00010000. 000000|00.00000000\rightarrow$ mind the separator after 6 zeroes in third octet.

The first valid configurable address will be

$10000000.00010000.000000|00.00000001$

But people here are removing $2$ subnets (all $6$ zeroes and all $6$ ones) to remove base address and broadcast address. Doing so will render the above completely valid address unavailable. Consequently, we'll not have any network from

$10000000.00010000.000000|00.00000001$ to $10000000.00010000.000000|11.11111110$, and
$10000000.00010000.111111|00.00000001$ to $10000000.00010000.111111.11.11111110$.

And we certainly do not want to do that. So the subnet must remain $64$, and each of them will have $2^{10} - 2=1022$ hosts.

Answer 1

C is the correct answer

Answer 2

Answer is in the link : http://www.techrepublic.com/article/subnetting-a-class-b-network-address/

Answer 3

IN CLass B we have 16 Bit for NETWORK_ID and 16 Bit for HOST_ID..According to question 6 Bit is chosen for subnetting

then we have 10 bits left in HOST_ID part

Now question is asking for Maximum no host per subnet (2^10)-2 = 1022

which is only in option C..NOTE: It is asking for Maximum no HOST

NOT Maximum NO OF IP ADDRESSES WE HAVE PER SUBNET

IF in quesstion it is asking for maximum no of IP addresses then we have 1024 IP addresses

There is difference in Maximum no of IP ADRESSES and maximum no HOST