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Network access issues after power failure

UPS failed after surge, causing power failure and reboot of domain controller.
- After reboot, none of the clients can access the DC.
- During reboot, the following error is reported: The system has detected an IP address conflict with another system on the network. The local interface has been disabled.
- The App event log has only 2 errors, both: USERENV / 1000
   - windows cannot access the file gpt.ini for gpo
   - windpws cannot query for the list of gp objects
- DHCP is handled by a Firewall. The DC is one of 4 computers with static IPs, the remainder are dynamic
- Although the DC local adapter has been disabled, I can ping the IP address assigned for that box
- The server and firewall have been restarted
- Most computers have access to internet, but the DC does not.
I need to restore network to normal operation ASAP. THanks
1 Solution
Sounds like you just need to determine which device on your network is picking up this IP.  Perhaps you could c$ into the system to determine which it is and from there ensure it isn't able to pick up this address?

Maybe just try a start\run\  \\192.168.xxx.xxx\C$ or just a \\192.168.xxx.xxx.  You might also try typing the address in questino into a web browser - I've had issues on occasions with printers latching onto reserved addresses and causing similar problems.

Obviously the IP range would be your range, not necessarily 192.168.xx.xxx  
Ensure that your statically assigned IP addresses are not part of your DHCP scope in your firewall. Even though the DC's address is static, if it is part of the pool, a client can pick up the IP address thus causing the IP conflict.
Your DC will never start if it detects an IP address conflict.
Make sure that the scope of the DHCP is not service IP addresses that could conflict with your DC and if so, make 'reservations' so a PC will never be assigned the same Ip as your DC.

After chacking that, the simplest way is to reboot your ethernet switch which will force all your ethernet (workstations) to get a new IP address from your DHCP server. If you have an extra switch, you can ping and move connections one at a time intil you can no longer ping the workstation that has the duplicate IP.

You could also change the IP if the DC temporarily, but you would also have to set your DHCP server to the new IP of your DC, especially if your DC is also your DNS and possible a WINS server. You could easily reset your clients by powering off your hub of switch. That's a rough way to do it, and if you have routes, DHCP agent relays and such from remote nets, then this would not be the way to go.

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  If you had a power outage like that there is a good chance that any little internet router (maybe you main one) or access point got reset to its factory defaults and is now conflicting with the static IP address on the server.
use psshutdown from the sysinternals package to shut down the system which is holding the IP, then you should be able to get your DC online.  Then, wait for the call from the person saying "my computer just shut off, and it said to call you"
I ran into this last week .. I fixed it by shutting down the server and unplugging all peripherals except for the monitor mouse keyboard and network card.. I found that the USB from the UPS was causing a conflict... wierd I know but it worked.
ironkernelAuthor Commented:
I'm not 100% sure why this worked, but the DC was reset to a different IP to get back online. The original IP was still in use but couldn't be tied back to any hardware even after cycling router. Cycled switch and the IP cleared. Still clearing some minor issues, but back in business. Thanks

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