ANother Device On The Network Is using Your Computer's IP Address?

It means you are using static IP addresses and another device on your network is using that IP address. You should setup the router so that it is using DHCP to assign IP addresses.

 

Actually, that's not true. My router uses dynamic addresses. I don't know too much about wireless tech, but I know my router is auto configured with DHCP, so is my laptop, and my brother's laptop. But this tends to happen to me a lot. Actually, don't most things use dynamic ip addresses? I can't ever remember using a static address...

 

Yes, this happens to me on occasion as well, and my router is configured to use DHCP. I think it's a problem or temporary quirk of the router itself.

To the OP:
This may be overkill, but I've found the foolproof way to fix this is to do the following:
1. Turn OFF the router and all devices connected to it.
2. Keeping all devices OFF, power the router on and let it fully boot.
3. Turn on the first device and let it fully boot and connect to the router
4. Repeat for all additional devices, turning them on one at a time and letting them fully boot and connect before turning on the next device.

 

Or you could just wait 5 or 10 minutes and let it sort itself out. Mine does that, at least.

As I understand it..... the router assigns addresses to all the devices that are connected to your home network. Default is that each device gets assigned an address "dynamically." Basically, "on demand". If your network devices don't change much, then the addresses they are assigned will basically just stick to them - while they are connected.

There are all sorts of ways that addresses can get rejigged. For instance, if you take a device off-line (say the MacBook you took to the local Tim's) and then reboot the router, it will reassign IP addresses to the other connected devices. It may reassign the address that the (hypothetical) MacBook was using to a different device at this point. When you connect the MacBook back into the network the first address the MacBook will try to connect with the last address it was assigned.... in this (hypothetical) case an address that has been reassigned when the router was rebooted.

And you get the error message....

In my case, I just leave the devices alone and they sort it out in a few minutes. They don't pay me enough to put on a b&w striped shirt and sent someone off to the penalty box.

I am open to being corrected by an actual network guru.... but this is what I understand, and certainly my real-world observations of our network in action are consistent with my mental model of what is happening.