Subnet identifiers

angry_monkey_show

Hi! I'm studying to take the net+ exam, and I've came across a question on a practice exam that I need a little explaination on.

The question involved assigning the highest IP on a subnet to the router.
The identifier assigned to the subnet is 192.168.96.0/20.

The part that's giving me trouble is the "/20" apparently the answer is that the highest IP within that given range is 192.168.111.254, but I have no idea what the /20 has to do with the subnet identifier. If anyone has any links, or can explain this to me, I would really appreciate it.

EdTheLad

An IP address consists of 32 bits, i.e. 4 x 8 bits
/20 means a 20 bit subnet mask i.e 255.255.240.0
/16 would be 255.255.0.0
/8 255.0.0.0

eurotrash

01100000.00000000 = x.x.96.0
11110000.00000000 = /20 (relevant portion)

the second row is the subnet mask, and the zeros determine the host portion. the /20 means the mask (1's portion) is 20 bits long (though i've only showed half the mask).

so the subnet is 0110 and you have 0000.00000000 for the hosts.
highest IP = (0110)1111.11111110 (all 1's is for the broadcast).
which equals x.x.111.254

angry_monkey_show

thanks. I wasn't thinking in terms of binary at all !!