I am running server 2008 r2 in a highschool and have an ip address conflict. All machines in my building have been assigned a static IP address, but I have also set up a DHCP server for faculty that is bringing in a home device that would like internet service. . I have a static ip address assigned to a computer running Deep Freeze that serves 40 student machines. I need to NOT change that address, because if I do, I would have to create a new seed for all 40 machines it serves with the new ip address. These machines are in a workgroup and not on a domain. Here's my problem. Today, another device came up on the network with the same ip address and Deep Freeze stopped serving as a result. Even if you don't have knowledge of Deep Freeze I think someone will be able to help. What I need is to find out what device has the duplicate ip address and release it. How do I find what device that is? and, How would I force that machine to release the ip address? It could be possible that a student has assigned it to his or her phone/ipod/ipad/iphone device... Or if it is a computer in the building (it shouln't be as I have them all assigned with a static ip) how can I find out which it is?

To locate that conflicting IP, the easiest way is when it is online, PING it from the same subnet. Then look at your arp cache (arp- a from a command prompt). You'll see the IP address and MAC for that computer. Then log onto your managed switches and locate the MAC address via the MAC tables. The switch logs will tell you what port the MAC was found on. Then trace the cable to locate the computer. To prevent this, its challenging if people have local admin access to their systems. Anyone that can plug into a port, and can manage their system, can configure their IP settings. Guides and tutorials, visit ITGeared.com.

Thank you for quick response, I will try this tomorrow when back at school. People do not have admin access to the schools computers, but I believe this might be a device brought in from home by a student. Hoping is one of the school's machines so that I can just release the address. But if it is a student's device, I won't know who it belongs to and will need to know how to stop it. Also, I do not have any ports availabe for them to plug into. It is all Wifi. I will get back tomorrow after running arp -a. Thanks again for the tip.

To locate that conflicting IP, the easiest way is when it is online, PING it from the same subnet. Then look at your arp cache (arp- a from a command prompt). You'll see the IP address and MAC for that computer. Then log onto your managed switches and locate the MAC address via the MAC tables. The switch logs will tell you what port the MAC was found on. Then trace the cable to locate the computer. To prevent this, its challenging if people have local admin access to their systems. Anyone that can plug into a port, and can manage their system, can configure their IP settings. Guides and tutorials, visit ITGeared.com.

Hi, I would like to confirm what is the current situation? If there is anything that I can do for you, please do not hesitate to let me know, and I will be happy to help. Regards,Arthur Li TechNet Community Support

IMHO better way to block rogue computers is division of network into virtual ones and filtering by MAC address on network switches. Depending on the switch vendor ask for help the vendor's support and/or vendors's community/forum. Otherwise your problem would never end. Regards, Milos

IMHO better way to block rogue computers is division of network into virtual ones and filtering by MAC address on network switches. Depending on the switch vendor ask for help the vendor's support and/or vendors's community/forum. Otherwise your problem would never end. Regards, Milos