ip addresses are they unique?

[richnsue]

just curious, i was wondering how an ip address is generated. i mean, what keeps it unique? is it geographically based? if my machine is given an ip, can another machine on the other side of the world have the same one? is some sort of check done each time one is generated? hmmmmmmm!

[Swordfish]

Usually, a user when connected to the Internet gets an IP address from a block of valid IP addresses from a ISP.

All ISP's get fixed IP blocks, if i am not mistaken here, its from ARIN, APNIC,RIPE etc depending on on your geographic location.

(ARIN: American Registry for Internet Numbers.)

An IP addr is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 referred to as octets.

like 204.12.10.1

There are 5 different address classes:

Class A : 1 to 126
Class B : 128 to 191
Class C :192 to 223
Class D : 224 to 239
Class E : 240 to 254

Class D and E addresses are reserved for multicasting. and testing, not for Internet.

Also, some IP address ranges that are not routable on the Internet.

Class A: 10.xx.xx.xx
Class B: 172.16.xx.xx - 172.32.xx.xx
Class C: 192.168.xx.xx

They are used for setting up internal IP networks like a Home LAN, Labs etc. behind NAT and stuff.

don't ask: how do you differentiate between them.....you will get into the world of subnetting.:D

[richnsue]

thanks for that swordfish:) very interesting.
can i ask another? using a firewall, if i need to manually open a port for a particular server eg to play a game, what is to stop someone pretending to be that server and accessing your open port? no more questions, honest!

[Swordfish]

Well, opening ports can leave your computer vulnerable.

You should only open ports when you absolutely need to( like what you said in case of online games) but usually you can getaway with it.;)

http://www.practicallynetworked.com/sharing/app_ports.htm

[cat5e]

If the port is open through the Firewall there is no need to pretend it opens so any signal can go in.

However it is like you left the small window in your bathroom open for a while.

I.e. who in the world knows that it is open, and why should some one go into your bathroom to steal the soup.

However if you have on your computer a copy of an International Credit Card Data Base, and the Vulture know about it you should be careful.

.