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Windows Radom IP Conflict Solution

The Problem

  • Every so often I would get a IP conflict with and a message like this one
    The system detected an address conflict for IP address **** with the system having network 
    hardware address CC-D8-C1-10-E8-19. Network operations on this system may be disrupted as a result.

    When I looked up the mac address it would point to a Cisco device which is particularly strange since I have only to cisco devices in my entire network.

  • Anyway the issue is apparently that when Windows NT 4 and higher binds a IP address it check to see if the address is taken even if that address is Normally this shouldn't be a problem, but initially Windows apparently binds before it binds it's real address. So what's the problem you might be asking well certain cisco switches and routers will reply to ARP requests for which has the effect of causing a IP conflict scenario on Windows causing the detecting interface to be disabled.
  • So long story short Microsoft and Cisco both did something that either one didn't expect

The Saga continues

  • Cisco has kindly provided a very nice KB article to fix this issue at this Link
  • Unfortunately for me I didn't have access to the Cisco equipment that was causing the issue


  • Lucky if you don't have access to your cisco equipment there is a registry tweak to fix the issue
Windows Registry Editor Version 5.00
windows/cisco_windows_ip_fix.txt · Last modified: 2016/06/21 12:16 by tschulz