Getting an error stating another device is using this IP? MAC Randomization?

[JPipes]

When connecting to one of our networks there is an error infrequently that states "Another device on the network is using your computer's IP address". When looking it up I found this article but I don't see any options for MacOS.

Edit: I should have been more specific, sorry. We're seeing the issue on multiple Macs. The device has a DHCP lease under a certain MAC address, goes to sleep, and then seems to have a new MAC address upon wake. The device then tries to connect with the same IP but obviously doesn't have the lease. That's why I wondered if it was a MAC randomization issue.

 

[iStorm]

Macs don't have that "Private (Random) MAC Addresses" feature. Even if it did, that doesn't necessarily have anything to do with IP addresses. They are two different things.

Is your Mac set to use a static or manual IP address? If so, another device with that IP may already be on the network. Try changing it to use DHCP, or some other IP address if you have to set it manually. (Most networks use DHCP, but I don't know what kind of network you're using.)

Use DHCP or a manual IP address on Mac

On your Mac, set up your internet connection to use DHCP or a manual IP address using Network settings.

support.apple.com

 

[casperes1996]

I don't think this is the root of your problem. To my knowledge, macOS does not do randomisation of MAC addresses yet even in Ventura. It will probably come one day but I don't believe it's there yet. Have you set up static IP or DHCP?

 

[JPipes]

Macs don't have that "Private (Random) MAC Addresses" feature. Even if it did, that doesn't necessarily have anything to do with IP addresses. They are two different things.

Is your Mac set to use a static or manual IP address? If so, another device with that IP may already be on the network. Try changing it to use DHCP, or some other IP address if you have to set it manually. (Most networks use DHCP, but I don't know what kind of network you're using.)

Use DHCP or a manual IP address on Mac

On your Mac, set up your internet connection to use DHCP or a manual IP address using Network settings.

support.apple.com

It's set to use DHCP

 

[Brian33]

When connecting to one of our networks there is an error infrequently that states "Another device on the network is using your computer's IP address".

You are not alone. I used to get this message (very infrequently) for one specific MBP on my home network. (It was retired about 6 months ago.) I never could figure out what caused it, which bugs me, but it never seemed to cause a problem other than the annoying message. IIRC the message would be there after waking up the machine from sleep, but it was still seemed connected (or able to immediately reconnect) to my WiFi network.

I use DHCP (dnsmasq on my router), and pretty much all of our devices have assigned IP addresses (i.e., the DHCP server always assigns the same IP address according to the device's MAC address). The DHCP server is configured so that unknown devices will get an IP address in a completely different IP range, so I'm sure the error was not caused by another device getting the MBP's IP address first. (I also checked my config file to be sure I hadn't assigned that IP to two different MACs.) It was odd.

This particular MBP was connected via WiFi, typically. It was an older machine (15" Early 2011) running an old macOS -- High Sierra.

Not much help, sorry, but if you figure it out, I'd be interested to know what caused it!

 

[FreakinEurekan]

Obvious causes are something set to a static IP and then forgotten about, and not being skipped in DHCP. Print servers, Wi-Fi enabled printers, etc.

I’ve also seen networks with multiple DHCP servers set up, that start giving separate devices the same IP.

 

[FreakinEurekan]

Oh, one other common cause - if the DHCP server (i.e. the router) gets rebooted, it’ll lose its reservations table. So it might dole the same address out to one item, that’s still in use by another.