Why does my Computer Name keep changing in System Preferences-Sharing when I am not changing it?

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Level 1

60 points

Why does my Computer Name keep changing in System Preferences-Sharing when I am not changing it?

iMac mid-2011, Mac OS X Yosemite 10.10.3 with all updates, Processor: 3.4 GHz Intel Core i7, Memory: 32 GB 1333 MHz DDR3

This has been going on for some time. I keep finding that my Computer Name is being changed in System Preferences-Sharing-Computer Name. At first something kept adding a "-2", and now something keeps adding a "-3" on the end of my Computer Name and on the end of my local host name. I keep removing it and changing it back in both places, and it seems to take, but then I return to my iMac in the next day or two, and the "-2" or "-3" is back again. We have an Apple Time Capsule (802.11n 2nd Gen) LAN with Airport Utility 7.6.4 that is connected to a Comcast High Speed Broadband modem. The LAN is shared by two iMacs (both running Mac OS X Yosemite 10.10.3), one Apple TV (2nd Gen), two iPads, one iPhone 5, one iPhone 6 and three shared printers. Sharing is set up for File Sharing via AFP only for my Public Folder (me - Read/Write, staff - Read only, everyone - Read only), my Drop Box Folder in my Public Folder (me - Read/Write, staff - Write only, everyone - Write only), Printer Sharing (everyone can Print), and Bluetooth Sharing (Ask What to Do) only.

Any ideas how I can find out what is doing this and why?

iMac (27-inch Mid 2011), OS X Yosemite (10.10.3), 3.4 GHz-32GB RAM-Contacts 9.0(1579)

Posted on Jun 26, 2015 1:13 PM

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Answer 1

Best reply

Linc Davis

Level 10

209,547 points

Jun 26, 2015 3:57 PM in response to alp1116

There are several possible causes for this behavior.

1. Two (or more) computers on the local network have the same Bonjour name, such as "X's-MacBook-Pro.local". Resolve the name conflict by renaming one or more of them in the Sharing preference pane.

2. You have two simultaneous connections to the same local network: probably Ethernet and Wi-Fi. If applicable, disconnect the Ethernet cable or turn off Wi-Fi.

3. A Mac wakes from sleep due to network traffic. This is a bug in OS X that may only affect some models. You can avoid it as follows:

Open the Energy Saver pane in System Preferences and unlock the settings, if necessary. Select the Power Adapter tab, if there is one. Uncheck the box marked

Wake for Wi-Fi network access

if it's checked.

4. 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.

5. A third-party wireless router has incompatible settings or firmware. In that case, refer to the manufacturer or ISP for support. Restarting the router may help, temporarily.

6. If the router is an Apple device, it may need to be restarted.

7. A third-party Bonjour device on the network is malfunctioning. Finding out which is a process of elimination.

8. There is more than one DHCP server on the network. Typically, there would be two or more wireless access points configured to act as routers.

9. See this support article.

10. Back up all data. Make notes of your settings in the Network preference pane.

Triple-click the line below on this page to select it:

/Library/Preferences/SystemConfiguration

Right-click or control-click the highlighted line and select

Services ▹ Reveal

from the contextual menu.* A folder should open with an item named "SystemConfiguration" selected. Move the selected item to the Trash. You may be prompted for your administrator password.

Restart the computer and empty the Trash. You will need to recreate the network settings.

*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination command-C. In the Finder, select

Go ▹ Go to Folder...

from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.

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Answer 2

alp1116 Author

Level 1

60 points

Jun 26, 2015 4:14 PM in response to Linc Davis

Wow, thanks for all that! I'll start with turning off Wake for Network Access and see if that solves it. I do have both Ethernet and Wi-Fi turned on, so that may be the problem as well. I'll turn off Wi-Fi. However, with Wi-Fi turned off, I cannot use the Apple Maps app, as it says that I need to be connected to Wi-Fi to establish my Current Location. I guess I can just physically type in my address each time I want to get directions somewhere. If neither of those options solve it, then I will back up everything, note my Network settings, then trash and recreate my Network settings per your instructions. I'll let you know what worked. Thanks again Linc! You really know your stuff!

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Answer 3

Eric Root

Level 10

684,045 points

Jun 27, 2015 2:22 PM in response to alp1116

Another thing that has worked for some people is to go to iCloud Preferences and uncheck Back to my Mac.

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Answer 4

Barney-15E

Level 10

112,818 points

Jun 27, 2015 3:13 PM in response to alp1116

There really is no problem having both services enabled. You should be able to set up your router to provide different IP addresses to each service on your Mac by using the MAC address of each service. You can find each Mac Address in the Hardware section of the Advanced settings for each service in Network System Preferences.

You can have WiFi on, but not connect to a network, also. That will provide location services, but not internet.

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Answer 5

alp1116 Author

Level 1

60 points

Jun 27, 2015 3:59 PM in response to Linc Davis

Thus far the advice you gave to turn off "Wake for Wi-Fi Network Access" in the Energy Saver pane of System Preferences has solved the problem. I still have both Ethernet and Wi-Fi enabled on my iMac, and the problem has not recurred in the past 24 hours. We shall see if it continues to resolve it.

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Answer 6

alp1116 Author

Level 1

60 points

Jun 27, 2015 4:01 PM in response to Barney-15E

This is how I already have my network set up. As I noted below, thus far the advice that Linc Davis gave to turn off "Wake for Network Access" in the Energy Saver pane of System Preferences has solved the problem. No recurrence in the past 24 hours. We shall see if continues to work. And I have left Ethernet and Wi-Fi service enabled.

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Answer 7

alp1116 Author

Level 1

60 points

Jun 27, 2015 4:04 PM in response to Eric Root

I will keep that in mind. Thus far, the advice by Linc Davis to turn off "Wake for Network Access" in the Energy Saver pane of System Preferences has solved the problem for the past 24 hours. We shall see if it continues to work.

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Answer 8

Barney-15E

Level 10

112,818 points

Jun 27, 2015 4:17 PM in response to alp1116

FYI: On these forums, we can all see the responses you make to each of us, so there is no need to repeat the content in each individual response.

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