Duplicate IP Address error on standalone workstation

[DerekMcDonald]

Please bear with the long description of our problem...

We have an SDSL account with a series of eight static IPs. The router/gateway has static IP xxx.xxx.xxx.xx1. I've got a Windows 2000 server with two NICs. One is external, and bound to the single static IP xxx.xxx.xxx.xx2. The second is internal, bound to the standard 198.158.0.1. The network's internet connectivity runs fine.

I've tried to set up a second, standalone Win2k workstation on the internet (for various reasons I don't want it to be part of our network), plugging it directly into the router and assigning it static IP xxx.xxx.xxx.xx3. Giving it this IP address brings up the error that there is a duplicate IP address on the network, and needless to say I have no internet connectivity. Can't even ping any IP addresses.

I called our ISP. They were stumped, but in examining the router via telnet, they said that our router's ARP records showed all our assigned static IPs as bound to the Windows 2000 server's external NIC (its MAC address). I've looked at every possible setting on the machine, the system report, RRAS, IPconfig, and even the registry, and I can find no evidence that any other IP address is bound to that MAC address other than xxx.xxx.xxx.xx2. Unfortunately, I can't look at the router because the ISP bastards reset the password and want to charge me $200 to administer my own router... I do know that there are no special protocols (NAT, DHCP, firewall, etc.) set up on the router.

Anyone know what's going on? Thanks!

 

[welshguy]

Derek,

Wierd !
If you switch off the the workstation and try to ping

xxx.xxx.xxx.xx3 address from another machine - do you get a response ? If so try and use tracert to give you a clue.
Arp -a on the server and client should give you a list of IP addresses associated with Mac addresses that your server knows about -does this show up the IP address xx3 ?
You can use arp -d to delete the Ip address from the arp cache if need be.

Bit suspicious about your ISPs attitude though !!! I'd demand the password so you can check the router for yourself !!!
Cheers

 

[galberry]

Try shutting off you router and see if you still have a dup IP. If there is no dup IP you know the problem is from the router. Disconnect the router from the outside and turn it on. If you get a dup IP the router is the problem. IF you don't the problem is from the outside and you router is letting packets come into you LAN side.

As far as the ISP ask them a question like "What is the penalty for getting out of my contract, because if it's less then $200 bucks you've just lost a customer". All of a sudden they may be willing to waive the fee.

 

[DerekMcDonald]

Thanks, all! Following your advice we've narrowed the problem down to the server. Here's the new deal:

If I unhook the server (xxx.xxx.xxx.xx2) from the router (xxx.xxx.xxx.xx1) and start the standalone workstation (xxx.xxx.xxx.xx3), I get an internet connection. If I plug the server back into the router, the internet connection remains, I can ping between the two computers, and the server's internet access is not affected. If, however, I reboot the standalone workstation, I get the "duplicate IP address" error again, and the workstation has no connection.

Again, nowhere in the server's configurations, registry, etc. is there a record for the duplicate IP address (xx3). Nor does the server generate any error messages.

Any new ideas?