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Duplicate IP and Name exists on the network duplicate MAC addresses also

Posted on 2007-11-13
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Hi I have a network of 20 or so computers, 3 Windows 2000 servers, a Linsksys WiFi Access point, and an RV041.  Lately, ever few days, I start getting duplicate IP address on the network.  When I run a utility to see a list of netbios names and Ips and mac addresses, some of the systems have dupliate IP addresses, and even worse, 10 or so of the machines have the same mac address.  after rebooting all, and resetting the Linksys RV041 router/dhcp thing, all is well.....  for a while....  then it happens again.  All systems have up to date AV's up to date.

Question;  does any one have any help on this one, any help is greatly appreciated.
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Question by:SlickTech
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kulvinder_10 earned 500 total points
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Try to Replace your switch. Seems to me that your Switch is bad,
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by:SlickTech
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not the router, the switch.
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by:SlickTech
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????
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by:batry_boy
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Agree with kulvinder_10...sounds like your switch is not working correctly...try another one and see if the problem goes away...
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by:kulvinder_10
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Yes switch,
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by:SlickTech
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Cool, thanks, I do have 4 16 port switches, and the router wich has a switch in it.  Any way to narrow this down?
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by:batry_boy
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You'll have to get into each of those switches (telnet, web GUI, or console) and look at the local ARP table on each to see where you find duplicates...
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by:jtdebeer
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Check to see if DHCP is enabled on more than one device. (Also keep in mind that DHCP Server can also be running on your Windows 2000 Servers.)
DHCP is probably enabled on a managed switch or the Linksys router.

Disable / remove all DHCP servers and then only use DHCP on the Linksys.

This should solve your problem.


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by:SlickTech
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JTDeeber, thanks also, I did check that one first, the wierd part to me was the dup mac addresses.

Question, does shutting the switch off then on clear the ARP tables?
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by:kulvinder_10
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Yeh you can try that
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by:SlickTech
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Thanks it looks like it was switch, no more calls, thanks guys
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by:OrcaKnight
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Have you tried to remove the machine that shows a duplicate MAC address from your network and tried to then ping the IP? Wireless hacks sometimes duplicate MAC addresses in order to enter your WLAN, so that might be what is happening here. The other possibility is that, if you are running intelligent switches, you have more than one VLAN configured in a switch, and it is assigning distinct IPs to the same machines.
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