Multiple IP Address Conflicts

[Roey1984]

Hello

I`m getting emails from the Meraki Dashboard about an issue that our Security Appliance network has detected an IP conflict with two or more devices. 

It happens every other week.

Anything I can do to diagnose it?

Thank you!

[cmr]

I get the same when APs reboot as they seem to use 1.1.1.1 for a moment.  However there are usually only two MAC addresses and each is listed twice.  Is that what you see?

[Roey1984]

Sometimes i see the ip 1.1.1.1, But if you say that its something that is related to the AP rebooting or something like this, could be...

I dont know why it happens

[Tony-Sydney-AU]

Whenever I see IP address conflict, I like to check the offending MAC Addresses in Wireshark OUI Lookup Tool. This tool can return the Interface vendor so you can have a better idea of what device or client is related to this issue.

When the Wireshark OUI Lookup Tool can't find the vendor, then there is a good chance it's the Operating System doing MAC Address randomising.

Either way, in most cases it's like @PhilipDAth and @Brash explained.

[PhilipDAth]

I have also had this with IoT devices with both and Ethernet and a WiFi connection, and they bridge the two together.  Then the same IP address appears via two MAC addresses.

[Brash]

I also see this from time to time.

Whenever I've checked it's typically been an iPhone or Android phone.

My guess is that it's in part due to MAC Address randomization and the device requesting back or using an IP which it previously had, but the Meraki DHCP server detecting it as two separate devices. That said, I have no troubleshooting or captures to confirm this.