Q: Mountain Lion disconnect from Ethernet in sleep mode

These quotes come from

http://support.apple.com/kb/HT1379?viewlocale=en_US&locale=en_US

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

Application font

Serial printer location

Autokey rate

Autokey delay

Speaker volume

Attention (beep) sound

Double-click time

Caret blink time (insertion point rate)

Mouse scaling (mouse speed)

Startup disk

Menu blink count

Monitor depth

32-bit addressing

Virtual memory

RAM disk

Disk cache

CONCLUSION:

the reset of PRAM etc. does not affect network settings: Apple itself confirms it very clearly!!

So, still nothing helpful on this issue!

We hadn't any problems with 10.7 it's definitely a problem with 10.8 (and 10.8.1 and 10.8.2).

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.

@kevinwschafer,

I tried a manual IP and didn't have success.

Can you describe exactly what you did so that I can try it?

I assume you set this up from System Preferences>Network panel?

What settings did you select?

Thanks.

See screen shots below.  Hopefully this helps.

Sadly, no luck with using your settings

I have a case open with Apple who have forwarded the problem to Engineering.  I will report back to the forum if I get any useful recommendations to help those who remain frustrated.

For now, my Macbook remains on "never" sleep.

Kevin:

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 -

and then:

ifconfig en0 down

sleep 10

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

sleep 10

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)

MacBook Pro

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

27-inch

3.4 GHz Intel Core i7

Replacing with windows is really the worsed solution heard so far. Why did you go to Mac osx at the first place?

I am still convident this is a wake problem or bad network switch issue. There is one thing to try. Change network speed from autonegoiate to 1Gbps fdx and see if this helps.

I have the same problem with my iMac.

my iMac looses connection to my Ethernet only, but Wi-Fi.

OSX 10.8.2

iMac Mid 2011