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Duplicate Name Exists on the Network

Posted on 2009-07-13
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Last Modified: 2012-05-07
I am running Windows Server 2008 with Windows XP clients. About a week ago any computer that was rebooted started coming up with a "Duplicate Name Exists on Network" error. This happens on all PCs when they are rebooted. I've tried:

unplugging a PC from the network
leaving the domain and joining a workgroup
booting up in the new WORKGROUP and changing the computer name
rebooting then plugging the PC back in and I get the "duplicate name..." error  immediately

This is a network of only 12 PCs so I know there aren't any duplicates. Any ideas?
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Question by:mmurraynet
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by:usacadena
ID: 24844176
Check:
that you do not have another pc configured with the same IP address in network connection ->LAN connection -> TCP.IP Settings

then
open a command prompt
type:
ipconfig /flushdns
nbtstat -RR
arp -d
reboot

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by:mmurraynet
ID: 24844304
Done. Still no dice.

When I ping DESK03 (computer name) while it is unplugged I get no response so nothing out there is using this name. "Ping request could not find host...". I ran through your commands:

NetBIOS Names Resolution and Registration Statistics
-----------------------------------------------------------------

Resolved By Broadcast          = 1
Resolved By Name Server      = 0

Registered By Broadcast       = 0
Registered By Name Server   = 0

After I did all this I unplugged the PC, changed the computer name to DESK03b, rebooted and plugged it back in. I got another "Duplicate name error". No matter what name I change it to I get the same error.
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by:usacadena
ID: 24844350
How was the OS installed? Was this PC imaged or cloned?


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by:mmurraynet
ID: 24844366
Well, DESK03 was installed from CD but this is happening to every single PC on my network. There are various flavors of install involved. I forgot to add that some of the PCs are Vista as well.
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Expert Comment

by:loftyworm
ID: 24844403
This is happening on all the PC's and 2008 server, or just the one?

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by:loftyworm
ID: 24844414
Are you using WINS?  download and run browmon.exe (sysinternals I think) and find the master browser and reboot it.  does that help?

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by:mmurraynet
ID: 24844427
All of the PC's. I'm checking if it is also happening on the server right now.
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by:usacadena
ID: 24844530
need more info on your network.
how are PC connected via cisco router, hubs, switches?
Do you have a domain controller ans is DNS and DHCP running on it.?

How do client PC get ther IP address DHCP or static?
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Author Comment

by:mmurraynet
ID: 24845166
It is not happening on the DC.

I have three switches in a stack configuration which all devices are plugged into. Flat network, all devices are on the 192.168.168.x subnet. Except for the firewall of course which has an interface on the 192.168.168.x subnet but also has a routed IP on the interface connected to my ISP (Verizon).

The DC is running both DHCP and DNS. All clients pull IPs via DHCP. They are pulling IPs fine, but they all get the same "duplicate name exists" error messages.
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by:mmurraynet
ID: 24845169
Also, not running WINS. I'll have to try the browmon.exe utility tomorrow.
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by:loftyworm
ID: 24845361
reboot the server.  It is highly likely it is the master browser for netbios, and may need to reset its brain.  test it by shutting it off, and restarting a client.
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Expert Comment

by:usacadena
ID: 24845949
Try doing an nslookup for both the host name and ip address on one of the PC that is having and the issue then do the same and try to resolve the problematic name and ip on one that is not having the issue.  

Make sure you do not have more then one NIC enabled.

Send us you ipconfig/ all from one of the problem PCs and one that is not having a problem.
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by:boowhup
ID: 24846132
Sounds like scavenging isn't turned on in AD or it is set up poorly, this will likely cause an issue if your PC's tend to get different IP's from DHCP each time they boot (or you have changed something recently and they all have new IP's).

Delete all the DNS entries for PC's that are DHCP clients, and check all your static IP servers/clients have only one IP entry (per NIC of course). Then restart the clients, you shouldnt need to restart any servers. This should get you running (assuming I'm right). Then look at your scavenging setup (if it's even turned on that is).
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Accepted Solution

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mmurraynet earned 0 total points
ID: 24848651
I've figured it out. Since it kept happening even after I changed the computer name I decided this wasn't an AD issue but a NetBios issue. I threw a packet sniffer on the network and every time a PC booted I would see NetBios broadcasts coming from that PC. This is normal. But for every NetBios packet sent by the PC I would see a NetBios packet from the firewall. Upon further investigation I found that the FW had "IP Helper" with NetBios support enabled. I disabled this and the problem went away. Thanks for the help.
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