Forum Moderators: phranque
How many computers should I have before I can use class A ip addresses?
If I have just two computers and I use class A addresses, what will happen?
If I am applying for an IP address, how can the isp know I really have 2 computers or 50 computers?
Why cant I use any ip address at all but have to apply for it?
where are ip addresses kept?
In a flat topology, a class A address range will get 16777214 hosts onto the network. If you decide to subnet that space you'll have fewer available addresses because each subnet has two broadcast addresses, the first and last address in the subnet.
If you use a class A address range for just two hosts you'll have many, many ISPs beating down your door with lots of money. You'll also look mighty silly. (You probably won't be able to buy yourself a class A without a very, very large pile of cash.)
The ISP doesn't know, and probably doesn't care how many hosts your really own. They'll only allow traffic from your specific allocated range of addresses, so if you try to use more than your allowed addresses, nothing will happen with the extra hosts.
You want extra IP addresses if you want to have separate internet-available hosts. If you want a bunch of machines in an office, you could use NAT with a fake internal IP addresses (10/8, 172.16/12, 192.168/16).
You have to apply for an address so the ISP and backbone providers know where to send traffic from and to.
If you decide to pick any 'ol IP address, nothing will happen because your ISP doesn't know what to do with your traffic.
