Purpose of the Duplicate IP Scanner tool

The purpose of this tool is to rapidly determine if any two or more devices are sharing the same IPv4 address on the same subnet. If two devices share the same IPv4 address packet routing will not work correctly. Duplicate IP addresses are usually automatically found by the operating systems during the DHCP address assignment process. However, it is possible for a duplicate IP address to be assigned from a 'rogue' or unauthorized DHCP server present on a subnet or from a static IP address within the normal IP assignment range of a DHCP server.

Important: this tool uses ARP which is not routed beyond your current subnet. If you need to find duplicates on another subnet, you must move your computer to that subnet.

About the Duplicate IP Scanner Tool

The Duplicate IP Scanner Tool scans your subnet (or a range within your subnet) with ARP looking for duplicate IPv4 addresses in use by two or more devices. Any duplicates found are shown with their IPv4 address, MAC address, network interface manufacturer name and hostname. Important: to find duplicates on another subnet, you must connect your computer to that subnet.

This tool is fully functional in the demo version. Do not purchase NetScanTools Pro thinking the full version will do more. The scanning is limited to your current subnet. You have to change your IP and subnet to scan other subnets.

Related Tool Links

Duplicate IP Scanner Screenshot

Duplicate IP Scanner Screenshot

How the Duplicate IP Scanner works

The tool checks every IPv4 address in the range specified and looks for two or more devices using the same IP address.
It scans the IPv4 devices with ARP packets and collects the responses. Any responses from different devices using the same IPv4 address are noted and displayed.

Displays Duplicate IP Addresses along with the MAC Addresses of the Duplicates.
Shows all duplicates along with the IPv4 address, MAC of each device, the manufacturer of each remote device's network interface and the hostname for each IP address (optional).

A video of the Duplicate IP Scanner Tool in action!

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ARP (Address Resolution Protocol) is a protocol which associates an IPv4 address with a MAC (Media Access Control) address (xx-xx-xx-xx-xx-xx) over an ethernet network segment. ARP is normally not routed beyond a network segment. This tool uses WinPcap to generate ARP packets. See also the ARP Cache tool for ARP cache manipulation and the ARP Ping tool for testing a single device on your LAN.