hello guys,

i can't understand the ip address and the subnet mask.


my first question is:

is the "subnet mask" only for the subnet?

given a public ip, and a subnet mask, can you tell which machine the ip is pointing to inside the a subnet?

for example, if i visit this http://whatismyipaddress.com/, it will tell me that my ip address is

234.247.121.220

and from my windows 7 settings, i know that my subnet mask is 255.255.255.0. so that means, i am the number 220 machine inside the subnet?

BTW, I'm using the wireless of my school.


or, the subnet mask is only for the subnet , it has nothing to do with my public ip?

from my windows setting, my ipv4 address is 192.168.1.35 my subnet mask is 255.255.255.0, so really i am the number 35 machine of the subnet??




the second question is, if the subnet mask is only for the subnet, then why people say that ip address can be divided into class A, B, C and D??

does a public ip also fall into one of the four classes?

if public ips also have different classes, then the overall ip addresses cannot be 2^32, because if you look at the class A ips, there are only 256 ips in total.




my third question is, if i want to build a home wireless network and i have two machines and an ap. why should i use the subnet mask 255.255.255.0?

why can't i use 255.0.0.0? and who invented 192.168.x.x ??? why not something else?

can my ipv4 address be set to 175.0.0.2 and use 255.0.0.0 as the mask?



if i were the inventor of the whole IP thing, i would give each public machine or a router an unique ip, but within each subnet, i would use integers, machine 1, machine 2, machine 3 ....

why bother with subnet maskes?