What is the broadcast address for the ip subnet?

Question

What is the broadcast address for the ip subnet 192.168.100.32 given a subnet mask of 255.255.255.254??

Can someone please tell me the easiest way to figure this out or for any other questions like this one as my head is fried.

Thanks!!

Answer 1

Theoretically with a subnet mask as you describe, which would only have 2 addresses in it (which would be the subnet address and the broadcast address), would have no room for any nodes.

.32 would be the subnet address and .33 the broadcast.

In practice .254 would not be used in the mask .252 which gives 2 nodes in addition to the subnet & broadcast addresses would be the 'tightest' subnet used.

254 decimal = 11111110 binary > 2 nodes (subnet & broadcast)
252 decimal = 11111100 binary > 2 nodes + subnet & broadcast
248 decimal = 11111000 binary > 6 nodes + subnet & broadcast
240 decimal = 11110000 binary > 14 nodes + subnet & broadcast
224 decimal = 11100000 binary > 30 nodes + subnet & broadcast
196 decimal = 11000000 binary > 62 nodes + subnet & broadcast
128 decimal = 10000000 binary > 126 nodes + subnet & broadcast
0 decimal = 00000000 binary > 253 nodes + subnet & broadcast

You may have noticed there is never a 1 after a zero and this is the major clue to figuring out how to subnet. Once you have that you can do C class subnetting in your head.

Answer 2

This fictional IP subnet gave only 2 IPs out for the sub, a .32 and .33, broadcast the subnet 192.168.100.32, IP code 0 or 1 to the IP of ...32 or ...33

Convert everything into the binaries, the 1s in the mask says subnet bits. The length and position of 0s are the IPs of individual cards. AND the IP and mask XOR for subnet and IP code.

Answer 3

Usually this would be 192.168.100.1 - it's standard for most OSes and anything else could break things in some network environments.

funny, been in the biz for ages but the issue has never really come up.

But a quick google search for ip calculators and similar searches comes up with plenty of great stuff, like this one;

http://www.subnetmask.info/