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IP Assignment Error 4199 - Conflict When New User Connects

rlwhitney asked
Medium Priority
Last Modified: 2012-05-06
We have an Ethernet 10/100 switched network, using a DHCP server called haneWIN DHCP Server, ver. 3.0.20. We're using 192.168.1.### as our network address (with the DHCP server on We have the DHCP address pool set to 200 - 240, which is plenty (most of our devices are statically addressed, in the 1 - 178 range). We have a laptop user (call him LAPTOP), who uses the same addressing scheme on his home network (even using the same gateway address). Every day, when he plugs his laptop onto the network and fires up his laptop, another user (call her WIRED) on the network gets a IP Conflict error:
EventID 4199 - The system detected an address conflict for IP address with the system having network hardware address 00:15:C5:3C:E6:D7.
I have confirmed that this MAC address is LAPTOP's PC. And LAPTOP's owner assures me that he shuts down the machine at home, they re-starts it here at the office (it's not in standby or hibernation).
By the time I get to LAPTOP's PC, it has been assigned a valid DHCP address.
So I'm trying to figure out several things:
1.      Since the error appears in WIRED's Event Logs, her OS must be detecting the error. But it only occurs once, and then (apparently) the DHCP server makes the new IP assignment, before whatever IP polling occurs a second time on WIRED's PC. Is there a setting to "hide" the message, or a timeout value which can help?
2.      Is there a way to force LAPTOP's NIC to drop a leased IP # when LAPTOP's PC is shut down?
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The way I understand DHCP, this is a "normal error".  LAPTOP has a valid lease on his home network, and at startup the OS attempts to renew the lease, fails, and broadcasts for a new address.

I suppose you could eliminate the error by asking the laptop user to run a command line "ipconfig /release" prior to shutting down.
The other option to try could be to have the user LAPTOP start his machine, and let it boot COMPLETELY before plugging it in to the LAN.

Or create a batch file on LAPTOP to run at startup to do:

ipconfig /release
ipconfig /renew

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asavener - We have other users with the same situation (I'm one of them), in which shutting off at home, then starting up at the office, doesn't cause an IP conflict. So I suspect it's a difference in the client PC, perhaps one of the more archane settings on their NIC?

MrJemson - I like this solution, and will use it if I can't find another fix. My first choice would still be to figure out why it's happening with this one laptop, and not with others.

Could also be that the DHCP server at his home as a longer lease time.


asaverner - No, I setup his system (several of us are using Verizon DSL at home, and have the same DSL router). I've set them all up with a 12 hour lease. That's why I keep coming back to LAPTOP's NIC. We're all running the same DHCP and network setup at home, and we're all connecting to the same network in the office, but LAPTOP's PC is behaving differently. I've even checked the switches in the office. He's going though the same switch as I am, so I don't think it's a switching timeout issue, either.

Another thought (which didn't strike me until I fired up my own laptop):  Check the client software on the laptop.  Thinkpads, for example, have "ThinkVantage Access Connections" which manages switching between environments.  Perhaps the laptop has something similar which is holding onto the DHCP address from the previous connection.


I never could find the reason why LAPTOP was doing what it did. But I installed this batch file into STARTUP, and it solved the problem.
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