Calculating number of subnets and hosts

Q_Ball

Hey guys,

Just a quick question. I was revising over some notes and i found a question about how many subnets and hosts a company can have. The question gave the subnet 255.255.255.224 and a class C IP address.

I dont think the IP address is necessaary, only that we know its class C. We are asked to work out the number of subnets and hosts per subnet.

taking the 224 from the mask in binary:

11100000

means that the first 3 bits are the subnet number and the following 5 bits the host number right? if so then i get

for the subnet

000
001
010
011
100
101
110
111

which is 8 subnets. Do i take out 000 and 111 because there could be a conflict if the addresses 000 and 111 are reserved for special use (broadcast etc), giving me the correct number of subnets?

Do 000 and 111 only have one host (000 00000, 111 11111) and that 000 00001, for example, cant be used?

for the host

00000
...
11111

gives me 32 hosts. Do i take away 00000 and 11111 again like when calculating the subnets?

Then would i be right in saying 001 11111 is a broadcast to all hosts on subnet 001?

Just trying to get my head around it, i appreciate any replies.

all the best

oscarBravo

www.subnetmask.info is pretty cool for this sort of thing. I always get confused with all this talk of Class C and stuff, I only do CIDR (/27 or what have you).