DHCP stopped working

I have a small LAN with about 50 PC's, and today when people logged out and then logged back on they can't connect to the DHCP server.  I have checked the AD server that serves DHCP and the server is up and running,  If I run ipconfig and release/renew the renew fails stating it can't connect to dhcp server.  I have restarted The DHCP Client and Server in the AD server with no luck.

Why would the DHCP Server become invisible ?  These systems have been running for between 2 and 5 years??

They are seeing the Domain Controller on the same server??? and execute logon.bat files???
Jeff_KingstonAsked:
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Jeff_KingstonConnect With a Mentor Author Commented:
All of the uninstall, added hardware, updates etc did not solve the problem.  Simply unplugging and waiting 3 minute and replugging the 3 Cisco 2950 switches magically solved the problem
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dtranceCommented:
Are you out of addresses?  Check your pool and reservations.  What does the event viewer say?
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Ernie BeekExpertCommented:
Did you check the logs on the server to see if anything is going wrong there?
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redeinternaCommented:
faulty nic on dhcp server.
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Jeff_KingstonAuthor Commented:
The error that I am getting in event viewer is from Userenv  ID 1030
"windows cannot query for thew list of Group Policy objects.
Check the event log for possible messages previously logged by the policy engine that describes the reason for this.
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redeinternaCommented:
maybe someone plugged in a router or wifi ap that has a dhcp server.ç this will cause ms dhcp server service to stop.
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Jeff_KingstonAuthor Commented:
No one has plugged anything into the network with DHCP service, I can rdp to the server and run other applications on the server so I don't think it is the nic card.  Besides AD and DNS run from that server
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
Have you recently updated your antivirus? What antivirus program are you running?
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Jeff_KingstonAuthor Commented:
I'm running Symantec, but this has been the same version for over 3 years
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
I'm assuming you're running Endpoint Protection.
I would check the Symantec Network Access Control service state. If it is stopped then start it and test DHCP. If DHCP still doesn't work when the service is started then uninstall Symantec and test.

If DHCP works then you can reinstall Symantec. It should still work.
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Jeff_KingstonAuthor Commented:
I am still running Symantec 10.1.5
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
OK, I don't remember the service name in SAV 10.1 so look through them and make sure the appropriate services are running. Advice for uninstalling and testing still stands. Give that a shot and let us know what you find.

BTW - why not install the latest version? you're entitled to it if you have a current subscription.
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Jeff_KingstonAuthor Commented:
I have found that replication is not running.  There was one source that said if replication not running then the error or one very similar will occur.

There s an issue with one of the servers and the latest version.
dnslint.htm
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
I don't see how this is related to DHCP. Is the DHCP server service running?
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Jeff_KingstonAuthor Commented:
Yes
Is ther some diagnostic that I can run and send to you to help, my understanding and description is apparently not helping.
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
OK. Have you checked the Symantec services like I suggested? Have you uninstalled Symantec like I suggested?

I am speaking from experience of troubleshooting DHCP issue.
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Jeff_KingstonAuthor Commented:
Which part of symantec do you think I need to remove.  I am afraid that if I restart the server then no one will be able to log on.  as it is now anyone who was logged on yesterday early AM and has not logged out can still use the system.  Anyone who has logged out cannot log back in and their system is assigned the dummy ip 169.254.x.x when dhcp tries to run
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
You should remove the Symantec Antivirus portion and leave the management. This will require a reboot as you mentioned.

Now, the issues that your workstations are facing are because they rebooted and are not getting a DHCP address and therefore cannot contact anything on the network. Soon, once the workstations DHCP leases have expired, all workstations will not be able to connect. Rebooting the server will not cause the workstations to loose their DHCP addresses but time will. We need to move on getting this resolved ASAP.

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Jeff_KingstonAuthor Commented:
As none of the suggestions were used and a simple restart of Cisco switches cleared up the problem this is the answer I accept
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