W2K DHCP is giving out duplicate addresses!

[linny]

Twice now in the last 2 weeks a remote site (2 Cisco routers and a leased line) has had PC's that announce a conflicting IP address. For example PC1 says there is a duplicate address & the offender has a 006... MAC address. DHCP says that the IP belongs to PC1 and correctly recognizes PC1 has a 0003... MAC. So where is the other conflicting PC? Languard found the culprit. His PC is also set to obtain IP from DHCP. The only thing that looked unusual is that winipcfg (oh yes, all 4 of the 2 conflicting pairs were W9x) showed when the lease was obtained and but gave no expiration date. I solved it by reserving the address in DHCP for the one that didn't show up - then the one that is following the rules got a new IP, but what's wrong with my DHCP? Why is it giving out dupes and how do I fix it??!!

Thanks!
Linny

 

[k12netguru]

Hi Linny,

Open up the DHCP mmc. Right click on your DHCP server and go to properties. Click on the Advanced tab and set the Conflict Detection Attempts to at least 2. This way the server pings an address before it gives it out. If it gets a reply to it's ping than DHCP knows the address is in use and trys the next available address.

W

 

[Bobg1]

The problem might have been caused by the dhcp server expring the lease, but the machine that was using it did not.

 

[gunthnp]

right thats why you have the dhcp ping 1st but still most times when I see this problem its the dhcp overload being a domain control policy machine and dchp/wins etc to mach stuff all at once bad dhcp packets go out

gunthnp