DHCP Problem

Earl Whittemore
Earl Whittemore used Ask the Experts™
I am having issues with my DHCP server having BAD_ADDRESS entries for a large number of addresses.  The Unique ID ends to be the reverse of the IP address in hex form. I have Conflict detection attempts set to 2.  It is only happening on the Scope attached to the secured wireless.  It seems to be about one bad address per minute or so. I've looked at the event logs on that server that I can find and there aren't any that match the time for the Lease.  Any troubleshooting tips?
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Hi Earl

Could it be that there is another DHCP server on the secured wireless? (check that possibility on the wireless, by checking on a multiple computers where they got their IP adress.

 Whats the lease time of your DHCP?

Andy BartkiewiczNetwork Analyst

It sounds like you either have a routing loop in your network or a rogue DHCP server. You may also want to check the lease time but I don't think that would cause these sort of problems.


So, I checked 30 computers and all of them have the correct DHCP server listed in ipconfig /all.  Any other guesses? Or is there another way to find a rogue DHCP server?
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hmm turn off the DHCP server you know, try connection to the Wifi, you should "not" get any IP. If so, one potential problem less.
Also have you checked the lease time in the DHCP, whats the lease time exactly?

Andy mentioned a routing loop. maybe he can go further with that to analyse.


The lease time for the problem scope is 8 days.  The other scopes have much shorter (Guest network is 90 minutes).  I turned off DHCP and it wouldn't connect (gave an APIPA address) I was wondering about the routing loop as well.
I'd recommend to turn down the lease time to 1-2 days first. then see what happens


Changing the lease time to two says seems to have fixed it.  I haven't gotten a BAD_ADDRESS in the last three days.  Thank you both for your help.

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