Can two computers have the same ip address?

No two computers can have the same IP address on the entire worldwide Internet!

Having made that statement, there is a caveat. There are address ranges which are referred to as "non-routable" addresses. These are often used in small businesses or on home networks. Many, many computers use duplicate non-routable addresses because of a trick in IP.

Referred to as Network Address Translation (NAT), the device (router) used to move information between these non-routable networks and the Internet keep the private (non-routable) address hidden in the small packets or envelopes that make up Internet traffic and assign only the WAN (Wide Area Network) IP address to the packets. To be able to be moved around on the Internet, every single one of these "interfaces" must have unique IP addresses assigned. The embedded non-routable addresses are then read only when packets come back to the private network from a web or some other server.

If IP addresses are like mail that gets sent through the post office, the address for each mailbox has to be unique for the mail to get to any certain building. But a building might have it's own internal mail system that takes all the pieces that came to that address and then sends them to the right person's office or room. That's a pretty good analogy for how the Internet works with addresses.

Many ip addresses are duplicated on private networks, but Internet accessible IP addresses are globally unique, and duplicate IP addresses cannot be used on a single network.

# IP addresses are analogous to telephone numbers - when you want to call someone on the telephone, you must first know their telephone number. Similarly, when a computer on the Internet needs to send data to another computer, it must first know its IP address. IP addresses are typically shown as four numbers separated by decimal points, or "dots". For example, 10.24.254.3 and 192.168.62.231 are IP addresses.

  1. If you need to make a telephone call but you only know the person's name, you can look them up in the telephone directory (or call directory services) to get their telephone number. On the Internet, that directory is called the Domain Name System, or DNS for short. If you know the name of a server, say www.cert.org, and you type this into your web browser, your computer will then go ask its DNS server what the numeric IP address is that is associated with that name.
  2. Every computer on the Internet has an IP address associated with it that uniquely identifies it. However, that address may change over time, especially if the computer is
  3. dialing into an Internet Service Provider (ISP)
  • connected behind a network firewall
  • connected to a broadband service using dynamic IP addressing.
  1. What are static and dynamic addressing?

In static addressing, each PC or device has its own IP address, chosen in the machines configuration, and this address does not change while we do not want to change it. this is good for a Network Manager monitor a network and know by his tables who is the user whose machine is involved in an accident (told by software which only knows IP addresses).

In dynamic addressing, there is a computer that "knows" the addresses that are available in a network in a given moment. Then, a PC coming to the network only needs to ask the DHCP (Dynamic Host Control Protocol) server for an IP address and this is valid only for the current session. This is very convenient for ISPs, Hot spots and any public places where the client users vary a lot.