What Is an IP Address Conflict?

 In Blog, Network, Security, Web Hosting


An IP address conflict occurs when two computers on a LAN (local area network) or the Internet have been assigned the same IP address. 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 local DHCP server.
  • A malfunction in the network’s DHCP server allows the same dynamic address to automatically be assigned to multiple computers.
  • An Internet Service Provider (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 issueindex
  • 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 work around IP address conflicts. See also – How to Release / Renew IP Addresses on Windows
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.


  1. C. E. Perkins, E. M. Royer, and S. R. Das: IP Address Autoconfiguration for Ad Hoc Networks. Technical Report draft-ietf-manet-autoconf-00.txt, Internet Engineering Task Force, MANET Working Group, July 2000.
  2. S. Thomson, and T. Narten: IPv6 Stateless Autoconfiguration, RFC 2462, December 1998.
  3. Kilian Weniger, and Martina Zitterbart: IPv6 Autoconfiguration in Large Scale Mobile Ad Hoc Networks, University of Karlsruhe, Germany.
  4. Sanket Nesargi and Ravi Prakash: MANETconf: Configuration of Hosts in a Mobile Ad Hoc Network, Proceedings of INFOCOM 2002.
  5. A. J. McAulley, and K. Manousakis: Self-Configuring Networks, MIL-COM 2000, 21st Century Military Communications Conference Proceedings,Volume 1, Pages 315-319.
  6. A. Misra, S. Das, A. McAulley, and S. K. Das: Autoconfiguration, Registration, and Mobility Management for Pervasive Computing, IEEE Personal Communications, Volume 8, Issue 4, August 2001, Pages 24-31.
  7. Paul R. Wilson, Mark S. Johnstone, Michael Neely, and David Boles: Dynamic Storage Allocation: A Survey and Critical Review, International Workshop on Memeory Management, September 1995.
  8. Kenneth C. Knowlton: A Fast Storage Allocator, Communications of the ACM, Volume 8, Number 10, October 1965.
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