Your employer is opening a new location, and the IT director has assigned you the task of calculating the subnet numbers for the
new LAN. You’ve determined that you need 50 subnets for the Class B network beginning with the network ID 172.20.0.0. How many host bits will you need to use for network information in the new subnets?
• We are taking a look at the class B network beginning with 172.0.0.0.0,while Converting this value to binary as:10101100.00010100.00000000.00000000. 32 bits in total, out of this the First 16 bits that are used as network ID and the subsequent 16 bits are used as HostID.Out of the 16 bits that are sued for Network ID the 2 bits namely Bits fifteen and sixteen (15 and 16) have been set and can't be changed and hence only 14 bits are used as network ID.
• Now so that we can divide this network into 50 subnets for class B network we will have to borrow a bit as shown below:
• 10101100.00010100.00000000.00000000=172.0.0.0.0,Adding 1 bit by borrowing from host portion and adding it to network ID will give it 10101100.00010100.00000000.00000000(0 shown in bold) or10101100.00010100.10000000.00000000 (1 shown in bold) will give us 2 unique subnets.i.e changing 1 bit will give us 2 power 1=2 subnets,thus changing 2 bits will give us 2 power 2 subnets =4 similarly changing 6 bits will give us 64 unique subnets.
• Which means and going by the above problem statement in case we need 50 subnets and we also need to change 6 bits in the Network ID to give 50 unique subnets.
