DHCP Server NACK Errors

Question

_{Wednesday, July 2, 2014 8:27 PM}

Hi

My DHCP server is acting very weird since I activated another scope on the server. I have 1 server with 3 scopes on it. The scopes are not heavily used. Since the addition of the 3rd scope, I am seeing a lot of "NACK" warnings in the logs (C:\windows\system32\DHCP\. I can clearly see that a client can try 100 times before getting an answer from the DHCP server. Some clients will never get an IP address when this occurs. I've been observing and trying to find out the answer since a couple of months already. Here are my observations and I'm expecting that maybe one of you folks can help me out with this;

My environment;

1 domain, 2 domain controllers, 2 DNS Servers and 1 DHCP server. All servers are running Server 2008 R2. There are 3 different scopes with 3 different subnets on the DHCP server. The problem started with the activation of the last scope on the server.

The issue is happenning only;

- When the 3rd scope is active. (If I disable the 3rd scope on the DHCP server temporarly, any clients request is processed without a problem)

- Only devices & printers are affected. This doesn't happen on a Windows/Linux/Mac desktop client. Workstations don't leave any "NACK" errors in the log and they have no problem with their requests to DHCP server. It's only Printers and small network enabled devices that are having an issue.

Until now, when this happens and we need to use the device right away, I am either temporarly disabling the 3rd scope on the DHCP server (for the time being that the client gets served) or whenever I can, I am setting up the IP addresses manually on the server.

I am guessing that the issue comes from that last scope as whenever it's disabled, we don't have any problems. My question is, if I setup a seperate DHCP server with only one scope on it, will it help me with these issues. 

Thanks in advance for all help.

Kubilay Elmas MCITP (Enterprise Desktop Administrator Windows 7)

All replies (1)

_{Tuesday, August 12, 2014 1:10 PM}

This problem has been solved. For anyone who is having the same kind of issues;

The DHCP NACK errors you see in the DHCP logs are probably related to your network equipment configuration and not to your DHCP server directly. In my case, it was a one of the switches that had a DHCP relay misconfigured.

Here are the 2 documents that helped me most to get the buttom of this issue;

https://www.ietf.org/rfc/rfc2131.txt

http://support.microsoft.com/kb/169289

Kubilay Elmas MCITP (Enterprise Desktop Administrator Windows 7)