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IP Address Conflict

By daniel ·
A Windows 95 machine that has been running fine on the network recently received the error message "The system has detected a conflict for IP address _____ w/ the sytem having hardware address _____. The interface has been disabled."

We are running NT 4.0 on a PDC configured with DHCP, with approximately 120 Win95 clients. I released and renewed the IP address, although the message still appears. This has randomly happened to other computers, and when I reinstalled the NIC and configured the computers to the network, this seemed to resolve the issue. However, this is alot of work, and I am still unsure of why this conflict is occuring. Is there any way to determine which hardware address this computer is conflicting with?

-Dan

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IP Address Conflict

by Bill_H In reply to IP Address Conflict

You can determine the hardware address using the ARP command. Refer to the MSDN article "How to Troubleshoot Basic TCP/IP Problems", which is located at:

http://support.microsoft.com/support/kb/articles/Q169/7/90.ASP

The following is an excerpt from the above cited article:

Clear the Address Resolution Protocol (ARP) Cache

The address resolution protocol (ARP) cache is a list of recently resolved IP address to Media Access Control (MAC) address mappings. The MAC address is the unique physical address embedded in each network adapter.

If an entry in the ARP cache is incorrect, IP datagrams may be sent to the wrong computer. To display all mappings currently in the ARP cache, use the ARP command by typing arp -a at a commandprompt. You should receive either a "No ARP Entries Found" message (if the ARP cache is empty) or a response similar to the following:
Interface: 10.1.1.3 on Interface 2
Internet Address Physical Address Type
10.1.1.7 08-00-02-06-ed-20 dynamic
10.1.1.254 08-00-02-0a-a3-10 dynamic
To remove any incorrect entries in the ARP cache, clear all entries using the following command:
arp -d <IP address>

Where <IP address> is an Internet address stored in the ARP cache. Use this command for each entry in the ARP cache until all entries have been deleted.

For more information on the syntax, options, and usage of the ARP command, type arp -? at a command prompt.

(If the above URL does not work, locate and remove any spaces inserted by the TechRepublic system.)

Hope this helps...

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IP Address Conflict

by daniel In reply to IP Address Conflict

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IP Address Conflict

by scarter3 In reply to IP Address Conflict

The Hardware address in the error message is the MAC Address of the "other" Ethernet Card , not the one you received the error on; unless, there are 2 Ethernet Cards in the PC, even an onboard Ethernet Card, on the Motherboard, and someone has manually assigned the IP to the additional NIC, or manually assigned the IP on the PC you are working on. Also, under Network Configuration, check TCP/IP for Dial-up Adapter, or any other devices you have, if they have the IP Address in question manually assigned, remove it. This would explain reoccurance of the error, since only the NIC connected to the Network does DHCP requests, and the Lease Period has not expired for it. Or, someone has manually assigned the identical IP address to a PC on your network. In addition, when you release and renew using WINIPCFG, the TCP/IP Stack may be corrupted, and has not cleared, so the IP Address, is not really released, this does happen sometimes on Windows machines in a Network. Try releasing the IP, then uninstall ALL instances of TCP/IP-not just the one bound to the NIC in question, then reboot the PC, reinstall TCP/IP, if necessary. This should fix the problem, without needing to uninstall and reinstall the NIC.

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IP Address Conflict

by daniel In reply to IP Address Conflict

I performed some of the above suggestions, however the only way to get rid of the IP address conflict is to reinstall the NIC drivers. It seems every few months one of our 150 machines will get an IP address conflict message. I was wondering if this may be related to corrupt drivers, and is common.

Thanks,

Dan

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IP Address Conflict

by Stillatit In reply to IP Address Conflict

On another computer, from a command (DOS) window, use nbtstat -A <ipaddress> to see the Netbios name of the computer which now has the address which the station with the message used to have.

Check both machines to make sure they are both using DHCP. Use winipcfg to make sure they are both talking to the same DHCP server. (Could someone have set up one by mistake on another server?)

If you have another DHCP server anywhere on your network for dial-in clients, vpn clients, etc., make surethat the two servers are using non-overlapping address ranges.

Use the DHCP manager to check the outstanding leases.

Good luck.

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IP Address Conflict

by daniel In reply to IP Address Conflict

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by daniel In reply to IP Address Conflict

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