How large is the environment? Multiple subnets? Any commonalities between the clients that can't get DHCP addresses (same subnet, same OS patch level, etc...)? Any firewalls in-between the clients and the DHCP server? Firewalls turned on, on the client side? Cisco helper address issue?
We use Wireshark here, and I think you'll find it well suited to what you are looking for,and it's free: http://www.wireshark.org/ I would put it on the DHCP server and a client and examine both. You need to see if the packets are getting to the DHCP server from the client. Chris Bodnar, MCSE Systems Engineer Distributed Systems Service Delivery - Intel Services Guardian Life Insurance Company of America Email: [email protected] Phone: 610-807-6459 Fax: 610-807-6003 From: John Hornbuckle <[email protected]> To: "NT System Admin Issues" <[email protected]> Date: 02/17/2010 09:49 AM Subject: Troubleshooting DHCP Yesterday I started having some DHCP weirdness that has grown today. I’m kind of stumped and need some guidance. DHCP server is Windows Server 2008. It’s also a DC and DNS server. It shows no errors relating to DHCP in Event Viewer, and there are plenty of addresses left in the scope. It can be pinged from client machines at >1 ms and no timeouts, and it can ping client machines with the same results. DNS is working fine. DC functions are working fine. DHCP, unfortunately, appears spotty. A number of clients (although apparently not all, from what I can tell) can’t get leases. If you run ipconfig /renew from a command prompt, they report that they can’t contact the DHCP server. If you manually assign an IP address, all works fine. So network connectivity seems okay—this seems to be strictly a DHCP issue. I’m guessing that I’m going to need a packet sniffer to further troubleshoot. I have to confess, though, that I’ve never in my life used one. I’ve just never needed to. So, can anyone recommend a free, simple packet sniffer I can run from a client machine to watch the DHCP traffic? And what, exactly, should I be looking for? John Hornbuckle MIS Department Taylor County School District www.taylor.k12.fl.us NOTICE: Florida has a broad public records law. Most written communications to or from this entity are public records that will be disclosed to the public and the media upon request. E-mail communications may be subject to public disclosure. ----------------------------------------- This message, and any attachments to it, may contain information that is privileged, confidential, and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are notified that any use, dissemination, distribution, copying, or communication of this message is strictly prohibited. If you have received this message in error, please notify the sender immediately by return e-mail and delete the message and any attachments. Thank you. ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
