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Duplicate Name On The Network

Posted on 2009-04-09
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Last Modified: 2012-06-21
Everytime anyone logs onto a computer for the first time every morning or after a reboot they get a duplicate name exists on the network. I check and there are not dups in AD anyone know what else could be causing this?
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Question by:chrisreston
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by:Alan Cox
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Wins? DNS?
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by:MrMintanet
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1.  Change the computers name and join a workgroup of any name.
2.  Reboot
3.  Change the computer name back to what you had originally wanted.
4.  Reboot
5.  Join the Domain
6.  Reboot

Done.

I am assuming that your computers are all imaged from a main image?
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by:chrisreston
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Some are, some aren't images. They have been running just fine for over a year. About two weeks ago we had our firewall fail and ever since that I have had email issues, and this dup name issue. I really dont want to have to go to every computer and do that but I will if I have to.
Thanks
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by:MrMintanet
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What firewall?  It sounds like you need to flush.  Did you replace the firewall?  Did you backup the firewall prior to crashing?
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by:chrisreston
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Yea the firewall is back up and running its a pfsense, if you can look at my other email issue maybe you can help me with that as well? And when you say flush are you talking of just flushing the DNS?
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by:MrMintanet
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Yes.  Flush DNS, DHCP and ARP.
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by:chrisreston
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Didnt work, im going to try the removing from Domain and then adding back to Domain. This is frustrating.
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by:chrisreston
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Ok now I have a big problem, I took a computer off of the Domain and put it in a work group. Rebooted, logged in as local admin, tried to add it to the domain again and cant, it tells me a computer already exists with that name, no matter what I make the name of the computer I get that error. Even though it does not exist. Any ideas? I have never seen this before.
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by:MrMintanet
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>>1.  Change the computers name and join a workgroup of any name.
2.  Reboot
3.  Change the computer name back to what you had originally wanted.
4.  Reboot
5.  Join the Domain
6.  Reboot

Did you do this?
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by:chrisreston
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No I will try that now,

I did the following
1. changed the pc to workgroup
2. rebooted
3.changed the pc name, and tried joining domain
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by:chrisreston
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It wont let me change the name, or add to work group with the network plugged in. I get duplicate name, even for a workgroup i just make up! So I finally change the name and to something really odd and add it to the work group something odd, with the network unplugged. I reboot, as soon as I plug in the network connection and try to change the name I get the same error, its the only computer on that workgroup! Any other ideas? I cant add it back to the domain either I get dup name even if I try something completely off the wall.
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by:MrMintanet
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Delete the computer from ADUC?  Then do this?  See, the problem is, the SID is what authenticates on the domain as the individual computer.
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by:chrisreston
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I already did delete it from AD. Whats weird is how it wont let me change the name even though its in a Workgroup now and not the domain, unless the network is unplugged.
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by:MrMintanet
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I have had this happen to me in the past.  I had to just disconnect the computer from my present do... wait.  Lightning.... it hit me

1.  Change computer name to something random
2.  Reboot
3.  Change computer to join workgroup named something random
4.  Reboot
5.  Join domain (DO NOT CHANGE COMPUTER NAME)
6.  Reboot
7.  Change computer name
8.  Reboot

I think you have to join the domain with a new computer name, then basically change the name once that SID has been confirmed with that specific name.  
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by:chrisreston
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Still no go! No matter what I change the name or workgroup to it wont let me it just says dup name!
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by:MrMintanet
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Bahh!!! Throw it out the window!  Hurry, before it spreads the evil to the other computers!

Please post a screen shot of the error message.  Please also tell me the version server you are trying to connect to.  I will dance with this.
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by:chrisreston
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Ok so I tried it on another computer and get the same thing. Every computer on my Domain gets the error of dup computer name on the network. They just ignore it! No matter what work group I try to join or what computer name I choose I get this error unless the pc is unplugged from the network. Once I plug it back in I get the error again. I even tried a program that gives your PC a new SID and it still gives me the error. I have given it a static IP, deleted it from AD, and DHCP lease. Im stuck!
error.JPG
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by:MrMintanet
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http://www.geekshangout.com/?q=node/14
First in DNS create a CNAME record instead of a normal Host(A) record.

The next thing to do is to create a new DWORD key in the registry

Got To:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters

Create a new DWORD with the following details:
Value name: DisableStrictNameChecking
Data type: REG_DWORD
Radix: Decimal
Value: 1

Then reboot the Host.

I have tested this on XP, 2003 and 2008 it should also would on 2000
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by:chrisreston
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Am I doing this on each workstation or on my DC?
Thanks
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by:MrMintanet
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DC
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by:chrisreston
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No go! Damn I dont know what else to try. Its weird because even for just the workgroup it tells me dup name on network exists.
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by:MrMintanet
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I wonder if you did something funky in BIOS to change this.  Perhaps you are using a pirated copy of Windows?  I think you should consider slamming your fist through something.
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by:chrisreston
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Nope its all legit, its all business software and computers. I thought about slamming it through my monitor but I really like the monitor I have!
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by:MrMintanet
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Run a Windows Repair.
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by:chrisreston
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Ok im very very frustrated now! I have done updates, ran repairs, have tried everything in this post. Today I brought in a laptop, my own, never on this network. Plugged it in and started it up and guess what... Got the same error message, its on its own workgroup, etc.... I just dont understand this... Anyone????
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by:chrisreston
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I just noticed something else, on all of my computers including my servers if I brows the network and the domain I see nothing under it at all.
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by:chrisreston
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More info, on my PDC this is what i get when I run
H:\>nbtstat -n

Local Area Connection:
Node IpAddress: [192.16

    No names in cache
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by:chrisreston
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Can anyone help with this?
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by:chrisreston
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Still waiting on help, anyone please? this is driving me crazy, i cant even add new computers to the domain
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by:MrMintanet
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I am sorry.  I have been training reindeer for the past few days.

Have you tried formatting the computer and starting over?  Let's see if that helps.
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by:chrisreston
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I don't want to have to rebuild my PDC from scratch. I don't think that it will help because even with the PDC off I still cant join a work group without it saying duplicate name. I have tried from several different computers as well with no luck when they are plugged into the network. I have to DC's how can I take one down and make the other take over?
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by:chrisreston
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Anyone this error still pops up everytime we log on to any computer on the domain.
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by:badgerdog
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Good news.  I have had the same issue and have discovered the cause and the cure.  The problem has nothing to do with active directory, windows, etc.  The issue is a routing "loop" occurring within your PFSense-based firewall.  Basically, what is happening is that windows NTLM/netbios broadcast packets are being reflected back (forwarded) from the firewall and as such appear to your computer as though there is another system on the network with the same name (not the same IP).

For a better discussion of the problem and cause, take a look at http://forum.pfsense.org/index.php?action=printpage;topic=5294.0

For the cure and solution, insert a new rule on the LAN interface to block netbios traffic.  

On PFSense version 1.2.2, you do this by:

1.  logging into pfsense
2.  Firewall -> Rules
3.  Select the "LAN" tab
4. Click the "+" at the bottom right of the list to insert a new entry
5. For "Action", select from the dropdown "Block"
6. For "Source", select any, and then click "Advanced"
7. Under advanced, and "Source port rant", select From:NetBIOS-NS  to: NetBIOS-SSN
8. Under "Destination port address", again select From:NetBIOS-NS  to: NetBIOS-SSN
9. Under "Description", I put, "Fix the "Duplicate Name on the Network" error."
10. Click submit
11. Next, be sure to also click the "Apply Changes" button to restart the firewall.

Let us know how this worked for you.  And, if it didn't work, please include the version of PFSense you are running, what hardware PFSense is running on, etc.  I am using the embedded version of PFSense on a Soekris 5501 based hardware.
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chrisreston earned 0 total points
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Issue went away on its own after we switched ISP
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