Dynamic IP address

An IP address conflict occurs when two computers on a LAN or the Internet have been assigned the same IP. IP conflicts between two computers normally render either one or both of them unusable for network operations.

How IP Address Conflicts Happen

Two computers can acquire conflicting IP addresses in any of several ways:

· A system administrator assigns two computers on the LAN the same Static IP Address.

· A system administrator assigns a computer a static IP address within the local network's DHCP range (dynamic IP range), and the same address is automatically assigned by the LAN DHCP server.

· A malfunction in the network's DHCP server allows the same dynamic address to automatically be assigned to multiple computers.

· An ISP accidentally assigns two customers the same IP address (either statically or dynamically).

· A mobile computer is put into standby / hibernate mode and then awakened later.

Note that other forms of IP conflicts can also occur on a network. For example, one computer may experience an IP address conflict with itself if that computer is configured with multiple Network Adapters. System administrators may also create IP conflicts by accidentally connecting two ports of a network switch or router to each other.

Recognizing IP Address Conflicts

On most Microsoft Windows computers, if you attempt to set a fixed (static) IP address that is already active on the local network, you will receive the following pop-up error message:

The static IP address that was just configured is already in use on the network. Please reconfigure a different IP address.

On newer Microsoft Windows computers having dynamic IP conflicts, you should receive a balloon error message in the Taskbar as soon as the operating system detects the issue:

There is an IP address conflict with another system on the network.

Sometimes, especially on older Windows computers, a message similar to the following may instead appear in a pop-up window:

The system has detected a conflict for IP address...

On Mac or Linux computers, a similar message will normally appear on screen.

Resolving IP Address Conflicts

Try the following remedies for IP conflicts:

1. For networks where IP addresses are fixed (statically assigned), ensure each local host is configured with a unique IP address.

2. If your computer has a dynamically assigned address, releasing and renewing its IP address can workaround IP address conflicts.
3. If your home router is believed to have a faulty DHCP server causing IP conflicts on the home network, upgrading the router firmware may resolve this problem.