Computers local host name is already in use

Sometimes this message means that you have two simultaneous connections to the same local network: probably Ethernet and Wi-Fi. Disconnect the Ethernet cable or turn off Wi-Fi.

Sometimes it happens because a device that gets its network address from the router wakes from sleep, and the address it was using before has been assigned to another device.

Rename the computer in the Sharing preference pane.

I just upgarded to MAVERICKS and the Map app asked me to turn Wifi on. So I did. I was previously using a wired Etherent connection. I then started receving the "...name already in use on network." I turn WiFI off, and the problem went away. Now, this will affect the MAP application, but the error message was quite a hassle. Net Net - TURN OFF WIFI IF YOU ARE ALREADY CONNECTED TO ETHERNET.....

Cheers

Steve

I also sometimes have ethernet and wifi. There are lots of reasons. My ethernet is fast. And wifi is necessary for syncing devices. I also use wifi to sync my password manager. I also use wifi to play things to Apple TV.

This is a super annoying situation that I somehow managed to fix after trolling message boards on and off for a couple years. I just got an SSD, did a clean install and whomp, it's back. This time I'm bookmarking and saving a file with the solution. Something had to be changed in terminal.

I'm confused in that I only get the constant popup if my WIFI is OFF. If I turn the WIFI on, then the message disappears. But there are lots of times where I need the WIFI off or don't have connection, so how can I stop the "This Computers local hostname [my i-mac name] is already in use on this network." when I'm not connected to a network?

I was having a similar problem. Here's my configuration and what steps I took that appear to have resolved it. I have a cable modem that is connected to an airport extreme base station. The airport extreme base station is set to function in bridge mode. The Mac mini computer where this problem suddenly began to occur was connecting to the airport extreme for its wireless connection but was getting its ethernet connection directly from the modem. This was a recent change that was made when I rearranged the furniture in my living room that made it more convenient to run the cable to the modem rather than to the ethernet port on the AirPort Extreme as it had previously been connected.

I didn't identify the final part of the problem until just now, but I think in hindsight that it only occurred when I used a mouse app on my iPhone to wake my Mac Mini. I am assuming that the iPhone app woke the computer via it's Wi-Fi connection, but then when the computer became fully awake it connected to the ethernet because ethernet is set as the top priority connection in the network system preferences. Regardless, disconnecting the ethernet cable from the modem and reconnecting it to the airport base station appears to have resolved the problem.

It's useful to have wired Ethernet and wireless Ethernet enabled and you go from you desk (wired) to meetings (wireless). This is a dumb error on Apple's part and it's not about being "twice as fast" but rather using a Mac in an office environment.

But… what if you actually want both network connections to be active?

Why would you want that? It doesn't make your computer twice as fast.

There may be a nuimber of reasons for why this is occurring, some of which could be in your Mac's settings but others might be from problems with your router. The suggestions in this article might be helpful for fixing the problem: http://reviews.cnet.com/8301-13727_7-57547889-263/tackle-a-macs-name-changing-wi th-sequential-numbers/

Thanks Link for the suggestion - this problem has been going on for awhile and I did not consider that it was related to having both wifi and ethernet connection simultaneously - I just disconnected Ethernet and expect things to clear up.

Linc, You sir are a genius - fixed my issue - both wifi and ethernet were connected. Thanks.

Linc, Thanks so much for this very simple solution. I'd forgotten that a few days ago I'd turned on wifi just as a test, and of course I'd neglected to turn it off. Problem solved! Thanks again.