We have a workstation on a domain that is set up to receive an IP address via DHCP just like all the other workstations. We have an address conflict of 192.168.0.115. I perform an ipconfig /release and renew on one of the computers, but it always gets the same address of .115 - even though there is another workstation out there (we have over 150) that already has the same IP.
How do I force this workstation to receive an IP other than .115?
Windows 2003 servers
XP Pro workstations
10/100/1000 Ethernet
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We have just 1 DHCP server. Strangely, when I view the the leases handed out on our DHCP server, .115 does not show up for either box - even though it falls within the scope. I know for sure one is configured for auto IP, not sure about the other device, since I don't know what or where it is. I am downloading WireShark to see if it will give more info on the other .115 machine.
Depending on how your computers are configured you may be able to issue the command:
ping -a x.x.x.115
or:
nbtstat -A x.x.x.115
to see if you can find the computer name. On the nbtstat command the A must be upper case and on the ping it must be lower case. Wireshark is not going to tell you a whole lot about the other box except the MAC address.
If ping or nbtstat does not return a name, then you may want to download nmap and and see if you can find out what server services it is running and attempt to connect to it.
Neither returned a computer name. I did type in 192.168.0.115 into my web browser and it pulled up a login screen for username and password - although the entries I tried did not work. The login screen has a blue header with 2 keys and the lower section is grey. Looks like a Windows Server login, but I verified that none of my servers are using .115...
Guess I'll try downloading nmap... Thanks for your help thus far.
After running c:\nmap 192.168.0.115 it gives me back a mac address pointing to a Dell box. That certainly narrows it down, but I have mostly Dells in my shop...
I attempted to Telnet in, but it requires a username and password...
As to my original question, would you happen to know how to force a NIC to grab an IP via DHCP while omitting a certain address (.115?)
You could remove .115 from the scope or setup a reservation on the DHCP server for that PC. You do reservations using the PC's MAC address.
It is a bit interesting that you have a box that is running a telnet server on it, unless you are running Linux on some of your comptuers. Generally people don't enable telnet on Windows boxes.
On nmap if you use the -O option it will guess at what OS the computer is running. It is normally correct.
You can also telnet to port 80 on that box and type GET / HTTP/1.0 press enter and then press enter again. If it is a Windows box running IIS it will come back and tell you invalid request that it is a IIS server. When you type in the GET / HTTP/1.0 you will NOT be able to see it.
I just want to make sure that I understand your problem....
You have box that is being issued .115 from your DHCP server but gets IP address conflicts?
If you DHCP server is a Windows 2003 server you can turn on conflict detection (no more then 2).
I would also do an IP config /all on the client that is getting the .115 address with the conflict and see what DHCP server is giving it that address - you might have a rouge DHCP server on the network.
If you know the mac address of the other computer you can look up the port it is on if your switch is manageable. This might help you track it down by finding where it is plugged into your network.
giltjr - YOU NAILED IT! I tried "telnet 192.168.0.115:80" and "telnet 192.168.0.115 port 80" - but it could not open the connection when I tried these. Then I ran "nmap 192.168.0.115 -O" and it returned the info that it is a Dell PowerConnect Switch 5324. Somehow we neglected to turn off DHCP for this switch. Thank you e vanheel for your suggestions about conflict detection - I will look into that for the future.Thanks for all your help.
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by: giltjrPosted on 2007-06-01 at 17:09:52ID: 19199220
How many DHCP servers do you have?
I would suggest that you install wireshark and capture the traffic to see which DHCP server is serving up that IP address to it. It sounds like you have more than one DHCP server and the one that this computer is using has reserved that address for it.
The other possibility is that the other PC has that IP address statically assigned and so the DHCP server does not know that somebody else has it.