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Duplicate IPs on all LAN PCs

By stergios_nik ·
Hello.

We are experiencing a problem in our LAN.

Yesterday, suddently, all the PCs on the LAN reported a duplicate IP problem. This was happening everytime a client PC was trying to logon to the network. A dialog box was displayed that notified the user that the PC's IP was used by another PC.

The problem was affecting all PCs thus I thought that it might be a network switch problem.

I switched off the main switch for 2 minutes and then I switched it on, again. This solved the problem but after 4 hours the problem occured again and we had to switch it off and on again.

Today, we did not experience the problem but I would like to ask if someone knows the root cause of such incidents.

Is it the switch, or PC network card?

Also, are there any equipment (hardware / software) tools that I can use in order to determine the root cause of the problem?

Thank you in advance.

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by BFilmFan In reply to Duplicate IPs on all LAN ...

How are the workstations getting their IP address information? Static? DHCP?

If it is DHCP, check that your refrest period is not longer than the IP lease.

If it is static, either the switch is malfunctioning or someone has assigned duplicate addresses.

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by adamtechpro In reply to Duplicate IPs on all LAN ...

Bfilmfan is def on the right track. If you are using DHCP and have some devices configured statically its a good idea to filter out those static address in DHCP via reservations or exclude them form the IP address pool. The best thing to do is just reserve a block of addresses in DHCP and when you need to statically assign a device you can pick form the reserved pool you set up.
In the error log for the duplicate IP, i do believe it does show the ip address in conflict. (i think i does :)) From there you could check your DHCP address pool to find out the computer name currently assigned that IP address. If the IP in question is not in the address pool than that means it was a statically assigned address. IN addition, if the ip is there but theres no computer name it is most likely a device on the network causing the problem not a computer.

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by HAL 9000 Moderator In reply to Duplicate IPs on all LAN ...

As the problem appears to be the switch I would start off by placing it on a UPS to form a filter between it and the mains which if you are in an area with heavy industry can cause ripples or surges which can prevent a switch from working correctly.

Without knowing more I believe that the others are on the right track but I've seen many switches suddenly start working perfectly correctly once they have been removed from a direct mains connection.

Col

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by jawed.ahmed In reply to Duplicate IPs on all LAN ...

hi..
I am having the same problem, I have a medium problem of around 200 PCs and all of sudden since today morning I have started receiving IP conflict alerts on all my PCs...I suspect it would be some virus though Norton is not detecting anything and Google is not throwing up much..
anyone else having the same problem or found whta it is due to???

Jawed ahmed
jawed.ahmed @ adaniwilmar.in

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by stergios_nik In reply to

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by stergios_nik In reply to Duplicate IPs on all LAN ...

Hello.

I use static IP addressing (no DHCP).

I noticed that whenever I was expieriencing this duplicate IP problem the issue was always reported (first) by the same user. I focused on his PC and I replaced his network card. Now, for 1 week I have no problems but I am still monitoring the situation.

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by nwadri1 In reply to Duplicate IPs on all LAN ...

hi!

I too have the same problem, suddenly in between all machines start displaying "ip conflict" message. I have LinkSsys WAP54G wireless access point. If i power off the accesspoint, all my network is working again. Later on it gets solved automatically. But repeats many times, can any one help??

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