Duplicate IP addresses in a DHCP network

If you use a DHCP server to assign IP addresses in your network, and you find a device with a valid IP address that does not appear to communicate properly with the server or other devices, a duplicate IP address may have been issued by the server. This can occur if a client has not released a DHCP-assigned IP address after the intended expiration time and the server "leases" the address to another device. This can also happen, For example, if the server is first configured to issue IP addresses with an unlimited duration, and then is subsequently configured to issue IP addresses that will expire after a limited duration. One solution is to configure "reservations" in the DHCP server for specific IP addresses to be assigned to devices having specific MAC addresses. For more information, see the documentation for the DHCP server.

One indication of a duplicate IP address in a DHCP network is this Event Log message:

ip: Invalid ARP source: <IP-address>
       on <IP-address>

where both instances of IP-address are the same address, indicating that the IP address has been duplicated somewhere on the network.