How To Get Multiple Ip Addresses

How to Find a Duplicate IP Address

By Vince Sparlow

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In a TCPIP network, no two machines are supposed to have the aforementioned IP address at the same time. Only there are several means a "duplicate IP address" error can occur. In virtually cases, the indistinguishable IP addresses can be detected using the DHCP servers and checking the configuration of the machines on the LAN segment. In extreme cases, Accost Resolution Protocol (ARP) messages have to be monitored to determine which machines are in disharmonize.

Step 1

Verify that 2 DHCP servers practise not have overlapping IP accost ranges. For DHCP servers that are using either dynamic or automatic allocation of IP addresses, this is merely a affair of comparison all of the servers' IP address ranges, looking for overlaps. Even so, for DHCP servers using static allocation, you lot volition need to review each hard-coded IP address assignment. Because these are manually entered, it is easy for an administrator to make a error in an IP address consignment.

Footstep 2

Bank check each motorcar on the LAN segment that has the indistinguishable IP address to ensure that it does non accept the duplicate IP accost statically entered. It is not uncommon for an end user to statically define the IP address for their machine based on a previously assigned DHCP address. If you notice a machine that has been statically configured with the duplicate IP address, there are 2 options. The first selection is to reconfigure the machine to utilize DHCP and then it volition exist assigned a new address. The second option is to configure the DHCP server to end assigning the indistinguishable IP address. This is useful if the motorcar with the static configuration is a well known server in the surroundings and cannot take its address changed.

Step 3

If at that place are no address range overlaps in your DHCP servers and no motorcar tin be found with a statically defined duplicate IP address, find the 2 conflicting machines using a network sniffer. There are many free network sniffers including the Microsoft Network Monitor, ngrep, and snoop. Utilise your network sniffer to monitor ARP message traffic, looking for the ARP messages that use ii different MAC addresses for the same IP address. One time the 2 conflicting MAC addresses are found, you can find the two conflicting machines on the network that have those MAC addresses. You then need to clear each machine's ARP cache and force each machine to release its IP address and lease a new one from the DHCP server. On Windows machines, this is done with the ipconfig command.

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