IPhone with personal hotspot not appearing as a network interface (USB) in the Network preference pane on OS X

Over here the iPhone USB interface in the Network pane also keeps displaying 'not connected' when the USB cable is connected to the iPhone.

• Mac OS X: 10.6.8
• iPhone: 4
• iOS: 5.1
• iTunes: 10.6.3
• iPhone Configuration Utility: 3.5

The cause is a faulty /System/Library/Extensions/AppleUSBEthernetHost.kext, though the version 2.3.0 is correct, its size of 78 KB, 60.892 bytes is not.

A known to be working AppleUSBEthernetHost.kext for iPhone USB tethering is version 2.3.0, but 225 KB, 189.646 bytes.

The fix is:

1. In Terminal: $ sudo rm -r /System/Library/Extensions/AppleUSBEthernetHost.kext # to remove
2. Restart (not sure whether this is necessary)
3. Reinstall iTunes (in our case 10.6.3), this also installs the good AppleUSBEthernetHost.kext: download iTunes from https://www.apple.com/itunes/ and run the installer, this will install the correct AppleUSBEthernetHost.kext.

When tethering still doesn't work:

4. Apple menu > System Preferences > Networking > remove iPhone
5. add the iPhone again
6. hit the [Apply] button

PS According to our backup software somewhere around May 7th, 2010 a newer version of AppleUSBEthernetHost.kext was installed.

If you plug any cellular enabled iOS device with Personal Hotspot turned on to a Mac via USB, the Mac will automatically open a network connection using the Personal Hotspot.

So yes, your Macbook Air will be the 1 connection you see.

The second part of your question is a little trickier and the answer is both complex and confusing but I will try to explain as best I can.

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Based on older knowledge with other multiple interface *nix systems is that it will be a complete toss up as to which connection your Mac will use since both active connections could possible provide the same route to the destination for any network query.

I have even seen, on both Windows and Unix networks, traffic coming in on one network connection and going out on another, which rarely works well.

To get round this, in the Network panel you could disable the "iPad USB" in your default location, but then set up a new location where your "iPad USB" is not disabled.

Finally, the order of your devices should mean that if your wifi is above the iPad USB device in your list when both are enabled, it will get priority over the hotspot, but there are still caveats and this could still use cellular data, but of a lesser amount.