December 7th, 2012, 12:44 PM

Need Some Subnetting Help Based On Hosts
Hi guys I have a subnetting question and I'm hoping you guys can help me. Lets say youre given a block of 192.168.10.0 and youre told to subnet this for 60 hosts one one network and then 40 hosts on another. You do the calculations for the 60 hosts and thats all fine but then here is my question. What IP block do you use for the next 40 hosts? How do you subnet for multiple block of hosts using one address block (192.168.10.0). Im sorry if my question is unclear but Im hoping someone can help me
December 7th, 2012, 07:54 PM

"192.168.10.0" by itself isn't a block, it's an address. But let's pretend that's your starting address.
Let's say that you first need to create a network for 40 hosts. How many bits do you need for 40 hosts? 6; because 2^5 is only enough for 32 hosts. You have 32 bits in the address though, so this means you have 26 bits left over. So the netmask is going to be 26 bits. This makes your netmask 255.255.255.192 because 0b11111111 is 255 in base 10 and 0b11000000 is 192 in base 10. And since this is your first subnet, your subnet address is 192.168.10.0. Since your network has 64 hosts in it, the last address in the subnet is 192.168.10.63.
Let's say your second network is only 25 hosts. Now you only need 5 bits for the hosts. So this time your netmask is going to be 27 bits. So 255.255.255.224, because 0b11100000 is 224 in base 10. If you want to position it immediately after your last network, then your subnet address is simply the next available address, 192.168.10.64.
PHP FAQ
Originally Posted by Spad
Ah USB, the only rectangular connector where you have to make 3 attempts before you get it the right way around