Why do I constantly get IP address conflicts on my DHCP configured network.

John Hemphill
John Hemphill used Ask the Experts™
I currently have a Netgear FVS318 v3 VPN router configured to act as the DHCP server for my home network. Quite frequently, I get IP address conflicts on various computers on my network. My network consists of a mix of Windows XP, Windows 7, and Mac OS X all properly configured to use DHCP to obtain network addresses. Can anyone give me any ideas on where to look for this problem? It does not seem to impact my network performance or connectivity, it is just annoying.  Thanks.
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Do you have machines with static IP addresses? Make your IP's dynamic to avoid conflics
I have seen this behavior from Apple devices before where they grab an address that is not in use right now, maybe one they had before or in another network, or of a device that is now sleeping or gone, but the DHCP server doesn't know that so it tries to assign it and you see duplicate IP messages.

The idea is it is trying to use the address space more efficiently by using an address no longer active but the problem is they are the only ones who are in on the game.


Thanks for the info. I have a single MacBook Pro in my network and it is always sleeping/waking up. Do you know any way to force it to use DHCP properly?
Every computer on a network is assigned a unique Internet Protocol (IP) address so data from the Internet and other computers on the network is sent to the right place by the router. IP addresses can be fixed but on most home networks they’re set ‘dynamically’, by the router, which allocates them when a PC is switched on. This is called DHCP or Dynamic Host Configuration Protocol and IP conflicts occur when a PC tries to use an address that has been assigned to another computer or wi-fi device. This can happen when a PC comes out of Standby or Hibernation mode, and the address it was previously using has been reallocated, or, more usually, the DHCP server in the router just gets in a muddle.

The quick solution is to go to Run or Search on the Start menu, type ‘cmd’ (without the quotes). In the Command window that appears type ‘ipconfig /release’, press Return and this deletes the currently assigned IP address, Next type ‘ipconfig /renew’, the router assigns a new address and you should be back in business. To stop it happening again try rebooting the whole system. Switch everything off (all PCs, the router and any other wi-fi devices) then begin a staged reboot, starting with the router, followed by the PCs and any other wireless devices.

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