I've successfully been using Internet Sharing on a MacBook Air to share a wired connection via WiFi to local devices. As of yesterday this stopped working, which may or may not be related to the recent 10.7.4 update (there are forum posts here regarding problems, but they report connection drops, not this altogether more bizarre behaviour).

Now when enabling Internet Sharing via WiFi the wired connection, promptly stops working. Some digging later and it appears the routing is messed up:

netstat -r [clipped]

Destination        Gateway            Flags        Refs      Use   Netif Expire
default      UGSc           11        2     en1
127                localhost          UCS             0        0     lo0
localhost          localhost          UH              1        6     lo0

Destination        Gateway            Flags        Refs      Use   Netif Expire
default            link#5             UCS             4        0     en0
10.0.2/24          link#5             UCS             1        0     en0

As you can see, after activation the WiFi connection is being used as the default route which is clearly nonsense.

Performing a route flush resets it correctly to, however the initial behaviour must be specified somewhere. Any ideas on how to correct this?

UPDATE: It turns out this has been reported previously on 10.7.2 in this forum post, however with no solution there either.

  • Was your configuration of network and InternetSharing working with 10.7.3? If yes, then you are facing a bug within the 10.7.4. – dan Jul 29 '12 at 21:20
  • It was working last time I tested before the update, but I've not found many people experiencing the same problem. Anyone have any knowledge of how OSX would be triggering this routing change? – mfitzp Sep 11 '12 at 15:12
  • I've been having the exact same problem on my MBA on 10.8.* through 10.9.1 which I currently have. While I'm sharing from Wi-Fi to USB Ethernet (so the other way around), my routes are messed up in exactly the same way. If I leave sharing on, they get messed up when I physically connect the USB ethernet. Also see apple.stackexchange.com/questions/73485/… . My solution for now is to turn Wi-Fi off from the GUI and then back on again when it gets messed up, after which the routes are back to normal and sharing works. – Dan Jan 19 '14 at 22:59
  • I see this on 10.10.3. My solution is to delete the new, bad route and add the good one back in manually every time. – James Roth Jun 15 '15 at 22:18

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