Duplicate IP Address

[ciscotx]

Ok, I have a general question on Win2003 Domain controller which is running Active Directory, DNS, DHCP, etc.. The question is, every once is a while I get a duplicate IP address on one of the client machines... How is this possible if I am running DHCP???? Or is just that it needs a reboot to clear itself??? Why is that????

 

[itsp1965]

It's quite possible to have a duplicate if you have one device that has a hard coded IP address that is part of your DHCP scope. If the DHCP console doesn't indicate anything, take a look at your switch ports to see who else is using the IP

 

[paella33]

Or maybe a rogue DHCP server that gives out part of the same range.

 

[ciscotx]

The DHCP scope does not indicate anything as far as a hard coded IP address.. I was thinking or of rogue DHCP but in order to issue IPs to domain computers it should join the domain wouldn't it???

 

[UpsetAdmin]

Check for Static MAC<=>IPs in the DHCP server. If none then try to get the conflicting PC to release/renew the IP through your network's DHCP. I don't think that in order to get an IP the PC has to be connected to the Domain, as DHCP requests occur before connecting to a domain.

 

[UpsetAdmin]

Also make sure the conflicting PC isn't using a manual/alternate IP address. Try to exclude the address from the scope of the DHCP server.

 

[Roadki11]

Or you have a person attaching a rogue device to your network. Ive had that before, an employee had a personal laptop and statically set it to one of my dhcp scope addresses. So... every once in a while we would get a duplicate ip nag when he decided to attach it to the network. Took me a while to figure that one out.

RoadKi11

 

[FredWagner]

I had an experience like Roadkill's - an employee of a guest agency wanted more network connetions, so he brought in a little box from home that did that - but it was a router with DHCP, not a hub. We were getting duplicate IP addresses too. Had to do a cubicle to cubicle search to find the device!

Fred Wagner

Fred Wagner