IP Address Conflict

What that message is telling you is that there is another machine on the network which is using or trying to use the same IP address that you are trying to use. The MAC address it is giving you is the MAC address of the other machine.

Causes for this could be:

a) Some user thinks this is the address he plugs into his IP address box, and does so, not realizing it is the address he should be putting into his DNS box.

b) Someone forgot to exclude this address from the address range you are handing out in DHCP.

c) Some admin set up a backup DNS box, with the same address, which was supposed to be a cold spare, but someone forgot and is trying to turn it on.

If your machine is up all the time, when the other computer boots, it trys to get that address, finds it in use, and gets 0.0.0.0 (no address). You get a message, but are not otherwise affected.

By the way, check whether it is the same MAC address all the time. IF DHCP is trying to give out the address, it may changeeach time.

If, for any reason, your box is down when the other box boots, HE gets the address, and you get nothing when you boot. This will mess up a bunch of people if your box is your primary DNS.

To find the other computer:
The easiest wayto find the other computer, unfortunately, is to turn off your box and let him have the address. You then use NBTSTAT -A to find the netbios name associated with the IP address. Since turning off your DNS server is a very bad idea, you may have to rely on your help desk to look for a user who constantly has problems using TCP/IP, and whose IP address is 0.0.0.0.

Good luck.

You can put your mac in DHCP via WIN 2k
just be sure to configure the proxy well to do that and your in business

Am a Tech administrator with mac and win 2k and it'S the win server that keep all info on all mac and pc's
if you put a mac in fixed IP be sure to leave out your IP adress N/A for the DHCP or win 2k will try to put the same adress twice !

hope you understand this answer friend !
Nick

Let me try again.

You do not have a duplication in MAC addresses.

You do not have to change any MAC addresses, anywhere.

Your problem is IP addresses, which you assign.

Your box, the DNS server, has an IP address which you assigned to it.

The Cisco has an IP address, which you assigned.

When users connect to the Cisco, they are either assigned an IP address by the Cisco, or they request a specific IP address from the Cisco.

Your problem is that either the Cisco is itself using the same IP address as your server, or the Cisco is trying to assign, or allowing someone to request, the same IP address as your server.

Step 1. Check the configuration of the Cisco box. Make sure that the IP number (not the MAC address) ofthe device itself does not conflict with anything on your network.

Step 2. When users dial into the Cisco, they are assigned an IP address for the session. The Cisco assigns these addresses using a mechanism called DHCP. In the Cisco setup, there is a parameter which specifies which addresses the Cisco may give to a dial-in user. Make sure that the range or list of numbers which the Cisco gives out does NOT include the addresses which your servers are using.

Step 3. It is possible to allow users to specify an IP address when they dial into the Cisco. If this is the case at your business, if it is not something you are selling, turn off this feature. It could be that a user is dialing in and requesting your server's address from the Cisco, and the Cisco is giving it to him. This would create the conflict you are seeing.

Step 4: If the users are allowed to request a specific IP address, you will have to track down the user who is requesting the server address for his workstation. The likely cause is that when the user set up his dial-up networking, he put your DNS server address in the "Request this address from the server" box.

Good luck.

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