switch could have been blocking broadcast ( DHCP request from client ) across bridges but allowing directed traffic. Not completely uncommon even though it's not an every day thing. Was one of my complaints on the older 3Com switches years ago, needed to 'reboot' them after a month or so to keep them from acting intermittently flaky
Erik Goldoff IT Consultant Systems, Networks, & Security ' Security is an ongoing process, not a one time event ! ' _____ From: John Hornbuckle [mailto:[email protected]] Sent: Wednesday, February 17, 2010 10:23 AM To: NT System Admin Issues Subject: RESOLVED: Troubleshooting DHCP Well, we seem to have fixed the problem. I reset one of our switches, and clients started picking up IP addresses after that. This makes absolutely no sense to me. We don't have multiple subnets, DHCP relay, or anything complex. This is about as plain vanilla a design as they make. And there were no other problems being exhibited. Normally if a switch was acting crazy, I'd expect lots of symptoms. But everything other than DHCP was working fine. Still, I'm going to check out Wireshark right now. I want to be prepared in the future. John From: John Hornbuckle [mailto:[email protected]] Sent: Wednesday, February 17, 2010 9:47 AM To: NT System Admin Issues 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. 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. ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
