How can I check repeated IP addresses in the network?

Duplicate IP addresses may cause a lot of trouble for network administrators. How can I detect duplicate IP addresses in the network? Can duplicate IP addresses be detected if there are routers in the network? The answer is yes. Some methods such as sending ARP packets to this IP address can detect duplicate IP addresses.

First, we need to know what causes IP address conflict. Once the two devices on the network are assigned the same IP address, an IP address conflict will occur, which will cause one or even two devices to be disabled or lost. IP address conflicts are usually caused by configuration errors. For example, if a network administrator assigns the same static IP address or assigns a static IP address within the DHCP range (Dynamic Range), the local DHCP server automatically assigns the same IP address or an error in the DHCP server, or, after the time is prolonged in the standby or sleep mode, the system returns to the network, allocates IP addresses, and uses them on the network.

So how can I check whether there are duplicate IP addresses in the network? Sudhanshu, a community member, recommends sending ARP packets to this IP address to detect duplicate IP addresses. All machines with the same IP address are restored to the MAC address. If you are using a security solution, we recommend that you block these MAC addresses. If you are using tools to manage assets, you can also use them to detect which users have duplicate IP addresses. Sudhanshu indicates that Nmap is a very useful network scanning tool. You can use Nmap to perform ARP scanning on the local subnet.

Another community member, blamkreg, said that if you are using a Cisco router, you will find that when it is connected to the network, or when the IP address changes, the router will send ARP for its own IP address, this helps detect duplicate IP addresses.

According to the information on the website supported by Microsoft, all Microsoft TCP/IP protocols can detect duplicate IP addresses in most cases.