IP Conflicts 2

[SysAdminMike]

Ok, so in my office we run Win2k3 Server, with the IP scope of 192.168.10.50-199 for DHCP.

Recently (maybe once a day) we have been getting alerts on just 1 machine (at most 1 machine a day) of an IP Conflict. I check the DHCP server and see nothing funky, but in order to resolve the issue I have to add the IP in question as an exclusion and then have the person release/renew to get a new IP. After this happens, I can still ping the old IP, but according to the server nothing has that IP.

I have made no changes to the server, but recently we have started to use Vista in the office and someone had told me via word of mouth that vista can cause these issues on non-vista (XP) machines.

Something else we have here (this was done before my time), we use ShoreTel phones and switches. The routing of the cables in our office is from the switch to the phone, and the phone has an output jack that goes to a computer. I realize now (This was right before I hit submit) that another cause could very well be this set-up. Today we had a user who connected wirelesly and was hard-wired. He got an IP Conflict, so I told him to turn his Wireless off (no need for him to use both), issue went away, and I was busy so I forgot about it. Later, he went into a conference room using his wireless and the issue was constant. Just thought I would add this little important tid-bit in.

Any ideas, thoughts or plans of action?

Thanks,

Michael

 

[burtsbees]

After this happens, I can still ping the old IP, but according to the server nothing has that IP."
Flush the arp cache, then try it.
" Later, he went into a conference room using his wireless and the issue was constant. "
Was the user setting his wired and wireless statically or DHCP? Did the user have both wired and wireless enabled again? Why does the user not just use the wireless all the time?
I would run Angry IP Scanner, write down all the IP addresses it finds, have everyone release and renew, run Angry IP Scanner again, and the addresses that match any addresses from the first scan---exclude those from DHCP.

Burt

 

[SysAdminMike]

I Just wanted to update you that the issue has been found and resolved.

Apparently (before my time) we had a IP 8000 ShoreTel phone put in, and it was put on the data subnet instead of the voice subnet.

The issue is that even after the the DCHP lease expires, the phone will not release that IP until it has been restarted, OR 1 week has passed. Stupid Stupid phone.

So, in DHCP I set a reservation for it's MAC Address, then I traced the cable to the switch and in the switch's configuration, set it to the correct VLAN and Subnet.

I appreciate your response.

Thanks,

-MF