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After looking at other posts I still can figure this out. I'll start at the beginning...

I inherited this network and I'm not the most knowledgeable about networking...

We have a AD DHCP Server that is also our DNS server, We were having some VPN issues (on the same server) and my boss decided to disable routing and remote access, which cleared the settings. We couldn't get it set back up correctly so we rolled back to a backup drive they created a number of months ago.

Since rolling back I've had Bad_Address listings in DHCP and there is a number of duplicate records in the DNS Forward Lookup Zones. We have less than 50 devices on the network but I have over 90 Bad Addresses showing. This server is currently running but we get IP address conflicts all the time on pretty much all the computers. I have had people do release and renew but it didn't help... I have also deleted and re-added the scope to no avail either.

Any help or ideas would be greatly appreciated and I apologize if I missed another post that has information to help.


  • Vince

UPDATE - We were looking at stuff and when we ping an address that shows as bad it doesn't respond but when we look at the arp it shows as the default gateway's Mac address...

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up vote 1 down vote accepted

Turns out our switches were keeping old arp information. All we needed to do was reboot them...


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Those BAD_ADDRESS junk entries usually get in there when something's already on an address and it tries to hand out a lease, be it from a statically configured system or old lease that it doesn't know about.

My recommendation since you've only got a smallish number of systems on the network (and assuming you've got a /24 or larger set up for this subnet), would be to put an exclusion range in the DHCP settings which covers all of the current address and BAD_ADDRESS settings. So, for example, if you've got leases and BAD_ADDRESSES scattered up to .150, then put an exclusion for 1-150, forcing the DHCP server to hand out higher address which should be unused and clean.

Once this has been done, wait it out for half of the normal lease time (8 days by default, so wait 4 days) and verify that all of the systems are now on the high addresses. Then you should be ok to clear out the BAD_ADDRESS entries, remove the 1-150 exclusion, and get back to normal.

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Thanks for the reply... we have actually been waiting for a while.. we also have other devices on the network with static IP addresses (our phones) that are excluded... we also have some servers on the same scope also... there isn't much we can exclude... – VinceM Mar 4 '11 at 17:39

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