Having another device within the same local network as your Synology NAS that has the same IP address can cause an IP conflict. This article describes how to use the ARP command to discover devices in your local network using the same IP address, as well as provides solutions for resolving IP conflicts.

The following error message is displayed when your Synology NAS detects an IP conflict at one of the LAN ports.

You may also see a similar message in Log Center.

IP conflicts are caused by having another device within the same local network that is configured with the same IP address as your Synology NAS. The ARP command helps you identify other devices that are using the same IP address.

Using the ARP command in Windows:

1. Press Windows Key and directly type cmd.
2. Right-click on Command Prompt and select Run as administrator.
3. Enter the following command in the command line:

arp -a

Using the ARP command in macOS:

1. Go to Applications > Utilities to open Terminal.
2. Enter following command in the command line.

arp -a

The ARP command will list all devices on the local network alongside their IP and MAC address in table format.

Check if there is another device using the same IP address as your Synology NAS. Change that device's or your Synology NAS device's IP address to avoid further IP conflicts.

Keep in mind that the IP might still be used by another device or by a device that is currently offline. We recommend using an unassigned IP address for your Synology NAS.