A duplicate IP address can cause disruptions in network connectivity. UniFi provides a system log to notify you if this ever occurs so that you can promptly address it. The two main causes for this issue are:
- Statically setting IP addresses on the device(s)
- A Rogue DHCP server on the network
Static IP Addresses
Duplicate IP addresses can result if you set a static IP directly on the NIC of a device, without removing it from your DHCP Range. To fix this:
- Select the Network with an overlapping IP address and navigate to its DHCP Range.
- Take note of the Start and Stop values.
- Change the range or change the static IP to ensure that the IP address is outside of the range.
- You may need to reboot the client to take effect.
Check for a Rogue DHCP Server
If there are no static IPs configured but still experience duplicate IP addresses, then you likely have a rogue DHCP server on the network. If you are unable to find the rogue DHCP server to remove or disable it, then we recommend enabling DHCP Guarding. To do so:
- Select a Network.
- Enable DHCP Guarding.
- Enter the IP address of your trusted DHCP server. If you have a UniFi gateway and are using the built-in server, use the network's Gateway IP here.
- DHCP offers will be blocked from all but the specified DHCP server.
Note: DHCP guarding requires UniFi switches.