What is an IP Address Conflict?

URLs blurred
Perry Mastrovito/Getty Images

An IP address conflict occurs when two communication endpoints on a network have been assigned the same IP address. Endpoints can be PCs, mobile devices, or any individual network adapter. IP conflicts between two endpoints 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 a LAN (local area network) 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 local DHCP server.
  • A malfunction in the network's DHCP server allows the same dynamic address to automatically be assigned to multiple computers. This can occur, for example, when a mobile device is put into a hibernate mode and then awakened later.
  • An Internet Service Provider (ISP) accidentally assigns two customers the same IP address (either statically or dynamically).

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 adapters. Network administrators may also create IP conflicts by accidentally connecting two ports of a network switch or network router to each other.

Recognizing IP Address Conflicts

The exact error message or other indication of IP conflicts varies depending on the type of device affected and the network operating system it runs.

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...

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 work around IP address conflicts. See also: How to Release / Renew IP Addresses on Windows
  3. If your broadband router is believed to have a faulty DHCP server causing IP conflicts on the home network, upgrading the router firmware may resolve this problem.