Q: Internet connection lost after sleep - Ethernet

I don't have Apple TV so I don't think it's a router issue. I don't think it's iTunes either. I have found that if I am logged out of my account and log back in it works fine.

It may be 2 separate problems then because my internet access seems to fail when iTunes is trying to sync with AppleTV. Perhaps the fix of installing the Airport Update worked for my original problem and now I have a new issue relating to iTunes/AppleTV.

No connection after waking up the iMac:
1) disabling the ethernet service, applying the change, re-enabling it and applying the change again makes no difference: no connection
2) disabling IPv6 doesn't make a difference: no connection

What did help was to disconnect and reconnect the ethernet cable, though it didn't solve the problem in previous tries.

I have a new i7 quad core. It has the same problem. It normally takes a few seconds before the ethernet connection comes back up on it own after coming out of sleep. I don't have this problem with my Mid-2009 Mac Book Pro.

In the last 24 hours the problem has reappeared regardless of any changes I make and has now got so bad that I've turned the Ethernet connection off completely and only running wirelessly. Connection speed doesn't appear to have suffered.

I'll watch this topic with interest to see if anyone comes up with a lasting solution and an explanation as to what causes it ! Hopefully it will come from Apple (lol)

Oh no - same thing is now happening with wireless...have all the attempts so far been red herrings?

I have same problem with new 27" i7 iMac running 10.6.2.

I am not having the problem with an old MBP 17" running 10.6.2.

Both wired ethernet to Airport Extreme.

I don't think the user community is going to find a fix for this one ....

Message was edited by: Baron015

Just for interest: Have you tried disabling "Wake for network access" in "System Preferences; Energy Saver"? It solved the problem for me completely.

Sadly (!!) I have tried this, along with all sorts of combinations of fixes posted here and elsewhere but to no avail. Sooner or later the problem resurfaces. Mean time between failures has improved however. Perhaps if I turned the iMac off every night I'd stop seeing the problem (even though it'll still be there), but that's not an option when I want to access the iMac via the internet when I'm on the road.

Looks like a portable copy of the hard drive is the solution for that scenario...and it'll save on energy, but it's hardly an elegant solution for the 21st century!

Trying now ...

I'm not sure how relevant this post is to this group, but because it drove me nuts for a while I thought I would add my experience. After four years of relatively good connections with the internet I just started having problems when the Mac came out of sleep. It would not connect. I tried restart of the computer and the modem (I have the direct ethernet connection at this time) and it would occasionally allow the connect. I read the posts in a few of the different forums and decided to try deleting the library preferences files mentioned in other posts. After two weeks of frustration I fixed the problem in about 10 minutes. By the way, I think the problem started after setting up a new Linksys router and Airport (neither of which are now connected).

Same here. Often when my iMac wakes from sleep there is no internet connection when my ethernet cable is pugged in. Disconnecting this cable and connecting it resolves the problem. The cable is connected to my Time Capsule, which is connected through WiFi with the router (Airport Express).
I decided to activate AirPort for the time being.

As a follow up to my earlier post, the "preference files" that I deleted are discussed in the following, very long thread.

http://discussions.apple.com/thread.jspa?threadID=1730909&tstart=0

After reading a bunch of the stuff, I deleted the preferences.plist and com.apple.airport.preferences files. I had to re-enter my network settings but it was worth it for me. Although the original thread was related to a security update, I figured I had corrupted the preference files. Apparently that was the case. Although it has only been about six days, I have had zero problems with the Mac connecting after sleep.

Not sure which exact preference files you mean. Could you post the exact names, please?

The files are located on your hard drive:

Library/Preferences/SystemConfiguration/preferences.plist
Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist

There are two other mentioned by others, Networkinterfaces.plist and com.apple.nat.plist, in the same location that I did not delete. If the first had not done the job for me, I was going to delete the next two. Make copies on your desktop of anything you delete just in case you need to get them back.