Hello We had a powercut today, which normally would be fine, and the UPS picked it up and proceeded to shut the server down. Once power was restored the server was turned back on. During the boot cycle the UPS cut the power. To the problem .. we had 3 computers that haven't been switched on for 2-3 months. These computers weren't going to be allocated elsewhere so we left them be in Active Directory. Obviously their DHCP leases had expired. Upon booting the server after the above had happened, I noticed that in DHCP I had two blank entries - they have every column entered apart from the name . The IPs that were allocated to nothing belonged to 2 out of the 3 computers above - I found this through DNS. I have no idea why this affected only 2 out of the 3. Today, I turned each of these 3 machines on in the hope that it would populate DHCP properly but it didn't and instead they picked up new IPs. I fixed a couple of stale rDNS records for these computers and they appear fine. I am concerned why I have these 2 entries in DHCP, and what (if anything) I should do about them. I am also concerned why I can ping them both! I am guessing that they're being routed to the server itself through some accidental and horrible means. Ping times range from 3ms to 250ms but primarily 3ms. Can these entries just be safely deleted from DHCP ? Or can I just let DHCP clean them up when their leases expire (the expire is set to 8days + server reboot time). Thank you for any assistance you can offer me.

You can safely remove any current lease from DHCP escpecially if you have "Conflict Detection" enabled. For 2008, go to the properties of IPV4, Advanced Tab. That way DHCP will send an ICMP (Ping) packet to the proposed IP lease before it actually leases it to a new client.In regards to the "mysterious" IPs on your network. They are real devices. Do you possibly have printers attached to the network that have not been configured with proper host names that can be detected by the DHCP server during the leasing process? They really can be any type of network attached device.The next step in locating these devices is to obtain their MAC address. From another device on the same segment, PING these "unknown" IPs. Then check your ARP cache (open a command prompt, and type arp -a). If you have "managed" switches on your network, you should be able to login to them and lookup the MAC address that was located in your cache for that specific IP that you are looking for. On the switch (if it is a "managed" one), will tell you what port that MAC address was found on. Then just follow the cable and you will find the device(s).There is no such thing as accidental routing or packet delivery. If you perform the steps above, you should be able to locate these devices. Visit my blog: anITKB.com, an IT Knowledge Base.

Thank you Jorge for your reply. You are right on the money. The IPs belong to two "smart switches" that had been bought quickly to replace those that had failed some time ago. Accessing the IPs through a browser led me to their control panels.