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windows 2008 R2 dhcp server is being flooded with BAD_ADDRESS. Have to manually clear them for computers on the domain to be able to pick an ip address. Any help in resolving this?

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Why is your DHCP still 2008 firstly. DHCP is almost the easiest system to migrate.

Bad address could be a number of things, private or random mac addressing by IOS or Windows, a device on the network targeting the DHCP to flood it, or rogue DHCP servers on your network, IP address conflicts, or faulty devices.

The reasons are plenty.

I would probably invest your time in a newer DHCP server, either recreate or migrate the configuration, update your helpers/relays and let the new one take over.

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I will second what Rod said, it’s way past time for a bit of updating..

But if you must, Bad address happens when the DHCP server asks ARP who owns an IP address it is about to hand out, It is expecting to get NO reply.

If it gets a reply, it means some machine on the network already has that IP address.

You need to look in the log and see if you can match the IP flagged as bad with a machine(+mac address) , that machine may have a bad NIC card, it might be a rouge wireless router or other device with a DHCP server on it…

Or if you have done something silly like having dhcp on each AD then there are other interesting failure modes…

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Agree with everyone else here. Server 2008 is too old to run DHCP (way back when, my 2008 server did the same thing). Whatever firewall you use can handle it. Azure servers cannot run DHCP so my Meraki does it just fine. (there’s the free alternative for you) :wink:

ADDENDUM: Your Windows server should continue to handle your DNS.

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Yes i agree the server os is way outdated and and upgrade is being worked on currently. reasons why it is still 2008 is a bit of a matter i cannot go into for some reasons. Thank you for your good suggestions.

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Your take true as well. Would work around that and see how it goes. thank you.

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Thank you that is a good take

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Assuming you have a licenses and another Windows server OS, the migration including building the new OS shouldn’t take much more than about an hour.

Being fair and giving time, half a day should cover it and most of this is done alongside the existing.

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True that. I am with the support team and the administrator is working on that. Thank you so much.

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Luckily, I have only ever come across this issue once in my career. A user needed to use Ubuntu for their role but we only provided Windows 10 laptops. I used VirtualBox and set everything up. All was working. The VM was using NAT to get access to the host’s network. For whatever reason, using VirtualBox’s NAT on our enterprise wifi caused BAD_ADDRESS entries on our Win 2016 DHCP server. This behaviour had not presented in setup, testing or handover, as the client was always using LAN. The wired NIC had a reserved IP. WLAN NIC did not. That seemed to be the difference. This was back in 2019, so I am hazy on the specifics but I believe the fix was to reserve an IP for WLAN NIC and enable some port forwarding in VirtualBox for the VM. I didn’t do any further investigation, so don’t fully understand the root cause from a technical standpoint. I assume it was along the lines of the VM’s NAT connection attempts failing in quick succession, therefore spamming the DHCP service, and trying to claim all available IPs until the pool was used up. I doubt this is happening in your case but I felt it worth mentioning this, as I didn’t expect something as inocuous as a VirtualBox VM to knock out the PROD DHCP service and cause a P1 on site. I’d advise you check the DHCP logs to identify any clients causing the BAD_ADDRESS entries and take them offline.

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Yeah, I remember early versions of Virtualbox used a bridged lan interface, that kinda,sorta,almost worked, but kinda also didn’t. It would do weird things like forwarding broadcast packets it wasn’t supposed to, and not forwarding packets to the local NIC and other annoying bizarre things :stuck_out_tongue_winking_eye:

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Thank you for this contribution.

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