HostName changes in OS X Yosemite, adds a (2) or more

I've seen this often on Macs running older versions of OS X. It's a DHCP cache issue.

Yes, we see exactly the same behaviour here but only since 10.10. My machine is now already "tlinder-macbook (6)".

Definitely noticed this happening to about half of my 10.10 clients. Hoping it's resolved with the next release.

Just noticed this on my Mac. A random computer name not used anywhere else on the network and its up to number 7. This is an old recurring issue but it sounds like its back, worse than ever :(

This has come about since Yosemite and is due to a bug in Bonjour Sleep Proxy Service not dropping the records when the client machine wakes from sleep. If you have an AppleTV, Airport Express or Time Capsule on your network, this will affect the machine.

I believe Apple are investigating. I haven't checked against the 10.10.1 betas to see if it's been patched yet

I disabled the Wake for wi-fi network access, and it seems that is working fine now. Hopefully the 10.10.1 Beta fixes the issue, if this is the case. Re-enabling the option in System Preferences, to check with 10.10.1 Beta 2.

i fought through this issue a couple of weeks ago. Disabling any variation of Wake for XX Access will prevent the client from registering with a Bonjour Sleep Proxy.

http://support.apple.com/en-us/HT3774