For a while now one of the Mac Books on our home network has been very quick to disconnect from the Wi-Fi network when the link is idle (and, by quick, I mean just a few seconds with no traffic is enough to make it drop the connection).
To make it even more annoying, the Wi-Fi network comes from a relatively new (1 generation ago) Apple Airport Extreme router, so there really should not be any compatibility issues between the laptop and the router. But, it almost never happens anywhere else.
In the console app, I see this line every time it happens:
kernel: AirPort: Link Down on en1. Reason 4 (Disassociated due to inactivity).
This morning it dropped the Wi-Fi within a few seconds of me hanging up on a Google hangouts video call.
The difference I see between the working laptop and the one that is dropping, is that the working one has the security for the network as “WPA2 Personal” (which is correct), but the one that drops had the security set to “WPA/WPA2 Personal” – the more relaxed mode that supports the older WPA encryption as well.
So, I deleted the entry from the Mac’s list of networks and added it back, but selected the “WPA2 Personal” option and it seems to have fixed the issue (I did need to turn the Wi-Fi off and back on to make this stick which shouldn’t really have been necessary).
If you have been seeing this, try it. If your router is set to allow both versions of WPA as well, you might want to change that to be just WPA2 as well (not sure whether that is needed, or if just changing the Mac setting would work – my home router was already set to be just WPA2).