These quotes come from
Note: OS X does not store network settings in NVRAM / PRAM. If you are troubleshooting a network issue, resetting it will not help.
Information stored in NVRAM / PRAM includes:
- Speaker volume
- Screen resolution
- Startup disk selection
- Recent kernel panic information, if any
Some earlier Macs store these settings in PRAM:
Status of AppleTalk
Serial Port Configuration and Port definition
Alarm clock setting
Serial printer location
Attention (beep) sound
Caret blink time (insertion point rate)
Mouse scaling (mouse speed)
Menu blink count
the reset of PRAM etc. does not affect network settings: Apple itself confirms it very clearly!!
So, still nothing helpful on this issue!
Well, after clearing the SMC and doing a safe mode restart, all was good for a few days. Then it started again. So...right now I have manually set my ip address, dns server etc. I did notice in the system log that the iMac wakes up every two hours I believe to fetch updates. I think that there is something going on when it send out a dhcp request on the Ethernet connection. When the WiFi is enabled, I am not seeing any errors in the log. When the Ethernet connection was dropping out, I was actually able to have it drop out by watching a YouTube video. I am not mac expert, just listing what I have noticed and have tried. It would be real nice if this was fixed in the next patch....very annoying!
I am not a whiz kid so I had to take my Mac to a local Apple store in Solihull, Birmingham, UK to the Genius bar, and a very helpful chappy, called Johnny, got a work around for me. Because I had taken my router with me as well, he set the computer and router up manually - ip address etc and its working fine, using WiFi. Because the Mac doesn't move around, this solution is fine for me. Its not ideal, until I get a new router. Hope by then Apple has sorted this out.
Well...it's been three days since I manually entered my ip address and have had NO issues. Seems like there must be some issue when the iMac wakes and polls/querries the dhcp server. And no, I don't think it's my router that has an issue. We have a few other devices that are connected via ethernet and none of them have issues.
Your search domain is incorrect.
This should be something like yourdomain.com. Otherwise leave is blank.
If have sporadious problems too on 10.8.2 and I have this since 10.7.1, but doing:
sudo su -
ifconfig en0 down
ifconfig en0 up
fixes it. It is annoying but since this problem only occurs once or twice a month it is not much frustrating for me.
It looks like during the wake up sometimes the interface is not reset. Which should be in the PM wakeup events.
Also a reboot fixes it to me. But this is not windows so not preferrable.
At the same time when I bring up my Wireless interface I don't have problems. So it is really the state of the wired adapter which is the problem.
I see I'm coming late to the game... I just got a brand new iMac a few weeks ago. Was surprised once by the network disconnect and no matter what I did, it required a reboot to fix this.
I use a manually configured IP on the ethernet connection. Wifi didn't appear to work, either though.
I've tried checking the "Network wakes up" box, but it looks like most haven't had success with this. Time will tell.
I hope this works, in which case at least I won't have to reboot:
ifconfig en0 down
ifconfig en0 up
Thanks for posting that.
It's odd that after allthis time, Apple hasn't fixed this issue.
I'm having a similar problem... If i am connected via ethernet and unplug cable then replug System Prefs -> Network says ethernet not connected and the network switch does not reconise that a machine is connect. Once I reboot MBP all is working again (logging out and back in does not fix it)
15-inch, Early 2011
Processor 2 GHz Intel Core i7
Memory 16 GB 1333 MHz DDR3
Software OS X 10.8 (12A269)
The problem seems to have been resolved by the Apple Genius in Birmingham UK. I am not a techie, but he set up my router to be connected manually with the routers specific address. Something like kevinwschafer's reple above. I have been running it for 2 weeks and no issues to date. My problem will come if I have to have a new router for any reasons. I am fortunate enough to live near an Apple store.
iMac 27" screen
OS X 10.8.2
Processor 2.7GHz Core i5
Memory 4Gb 1333MHz DDR3
It would be more problematic if I had to choose different networks manually, if I had a portable computer.
After trying so many proposed solutions with no luck at all and not seeing that Apple support are able to do anything, I went and installed Windows 7 on my iMac (Bootcamp). I wanted to see if the pb is a H/W one or just poor software power management by OSX.
With Windows I noticed the following:
iMac works perfectly, no loss of Internet connection after sleep.
And to my surprise, I use to have very short battery life on the Magic Mouse, with Windows, the life of the batteries is much longer, thanks to a better Bluetooth power management .
It is sad to see that Windows performs better on Apple H/W than Apple :-(
iMac 16 GB Memory
3.4 GHz Intel Core i7