Solved: message "You are not connected to the Internet" after idle sleep

Question

Summary: What worked for me was to turn off IPv4 and IPv6 on my unused interface.
The problem was that after my computer had been in sleep mode, Safari would say:
"You are not connected to the Internet."
or "softwareupdate -l" would say:
"This computer’s Internet connection appears to be offline."
Yet Firefox worked OK and traceroute also showed the connection was fine.
Digging deeper (though only later, after I found the command), "scutil -r" indicated a problem with DNS lookup:
$ scutil -r developer.apple.com
Not Reachable
$ scutil -r 17.254.2.129
Reachable
I'm using 10.6.6 on a Mini (model Macmini1,1), which has a wired ethernet connection on en0 and an AirPort on en1. I use the wired connection, but I also configured the AirPort just because, and then turned it off in the network preferences. I use a static (manually-configured) IPv4 address on en0 and DHCP on en1 (when it's up, which is only for experimenting). I don't use IPv6 as such, though I've left it enabled.
I was initially confused, thinking the problem was intermittent, though it's not. I tended to assume that because the display had gone into standby the computer must be sleeping, without checking that the power light was dimming and brightening, indicating sleep mode. Later I found the "pmset -g" command to display the power management settings. Among the settings is:
ttyskeepawake 1
This means that if I had a shell session open in Terminal, which I did quite often when investigating the problem, the computer put itself into idle sleep later than if I didn't have the session open. The times in Energy Saver settings in System Preferences seem not to be very accurate anyway. For instance, with the default computer sleep and display sleep settings of 10 minutes and a shell session open, I've seen it take 17m25s for the display to blank and a further 14m16s for the computer to sleep, for a total of 31m41s.
The problem only occurs after an idle wait. It doesn't occur after a software sleep (entered from the Sleep entry in the Apple menu or using the keyboard shortcut) or after pressing the power button momentarily.
One way I found to fix the problem was to turn the AirPort on and then off again through Network Preferences (or the menu bar item). Later I found that disconnecting and reconnecting the ethernet cable also fixed the problem. I hoped to find a better way.
What led me to this halfway house solution was noticing that if I turned the AirPort on and then off again, entries for en1 still remained in the routing table. These entries were for IPv6 link-local and multicast networks, as in this edited output from "netstat -nr":
Internet6:
Destination Gateway Flags Netif Expire
::1 ::1 UH lo0
fe80::%lo0/64 fe80::1%lo0 Uc lo0
fe80::1%lo0 link#1 UHL lo0
fe80::%en0/64 link#4 UC en0
fe80::216:cbff:fexx:xxxx%en0 0:16:cb:xx:xx:xx UHL lo0
fe80::%en1/64 link#6 UC en1
ff01::/32 ::1 Um lo0
ff02::/32 ::1 UmC lo0
ff02::/32 link#4 UmC en0
ff02::/32 link#6 UmC en1
Even with the AirPort switched off, ifconfig showed it as being up:
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 00:17:f2:xx:xx:xx
media: autoselect (<unknown type>)
status: inactive
I don't know if these observations are relevant, but anyway they led me to the solution (well, workaround). The way I finally fixed the problem was as follows.
1. Create a new location in Network Preferences. (This isn't strictly necessary, but it allowed me to keep the AirPort configuration (including my wireless password) intact in the default Automatic location.)
* Click on the Location pull-down
* Click Edit Locations...
* Click +
* Enter new location name (I called mine Wired-static)
2. Configure the Ethernet interface with its static address. (If using DHCP, I'd have skipped this step as DHCP is the default.)
3. Go to the AirPort configuration (even though it's shown as Off).
* Click on Advanced
* Click on TCP/IP
* Select Off for both IPv4 and IPv6
4. After clicking Apply in Network Preferences, a new "Location" item appears in the Apple menu between "Dock" and "Recent Items". Select the new location. This setting sticks across boots.
I hope this helps anyone else in a similar situation. Maybe if you use wireless it would help to turn off IPv4 and IPv6 on the Ethernet interface?

Answer 1

Try:
- A reset. Nothing is lost
Reset iPod touch: Hold down the On/Off button and the Home button at the same time for at
least ten seconds, until the Apple logo appears.
- Power off and then back on the router
- Reset Network Settings: Settings>General>Reset>Reset Network Settings
- iOS: Troubleshooting Wi-Fi networks and connections
- iOS: Recommended settings for Wi-Fi routers and access points
- DId the iPod ever successfully connect to the network?
- Does the iPod successfully connect to other networks?
- Do other devices successfully connect with your network?