IP Conflicts 2

[IMValori]

Several of our 95/98 wkstations have been individually coming up with an ip conflict with a certain mac address. We have DHCP Service installed on our PDC's. We have about 6 different domains. Some are complete trusts others are one way trusts. We have a layer 2 switch which will be replaced by a layer 3 switch soon. To fix the problem we just exclude the ip address from the scope which forces the wkstation to obtain another. This fixes the problem but then another computer a few days down the road has the ip conflict with the same hardware address. We have 250 computers in our LAN and I have tried locating that mac address but I can't find it. When you look at the scope and the leased addresses list, the proper machine is leasing that address but that ip conflict message says differently. Any suggestions?

 

[vinman]

If you have 6 different PDC's running DHCP, check the scopes on each one. In a "flat" network scenario like you describe you would need to have each DHCP server giving out a seperate range of IP's with no overlap to eliminate conflicts. Later on when you get a layer 3 switch you may be able to subnet your network, but that would necessitate a complete re-vamping of your TCP/IP scheme.<br>
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Some HUB/SWITCH management software (Cabletron's SPEL for example) allows you to do a search on MAC addresses. Another alternative if your switch allows "Port Mirroring" or has a "Roving analysis Port" would be to connect some sort of Sniffer device triggered on the offending MAC address and sniff each port on your switch until you find the offender.

 

[IMValori]

Thank you.

 

[RTurske]

Here is a web site with the vendor codes for the MAC addresses. Maybe knowing the vendor of the NIC card will help you find it. Also, Network Associates makes a program called Sniffer Basic that will help you in the port Mirroring project. You can download a trail version of the software for this one time fix, but it is a good tool to have around.<br>
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Vendor List<br>

http://www.cavebear.com/CaveBear/Ethernet/vendor.html<br>

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Sniffer Basic<br>

http://www.networkassociates.com/asp_set/buy_try/try/products_evals.asp

 

[Zelandakh]

Have you checked the WINS database to find the name of the offending MAC card that hogs the IP address? We found our hogger was a Jet Direct card set for DHCP that got the IP address but it didn't get registered as used in the database for some reason...<br>
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Failing that try sending a message to the IP address along the lines of phone me.<br>
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Z