I've had this happen a few times and I'm trying to figure out a quick way to deal with it. Most of the time I have no router or modem issues, but occasionally my iMac will show a connection to wireless, under network preferences it shows me connected with an IP address, but I can't access the web (or the router). From another device, when I log into the router, the iMac IP address appears as connected. Most of the time, the iMac is the only device that isn't working. This morning my phone, sitting right next to the iMac, was connected solidly. After shutting off the wifi multiple times without any fix, I tried logging off, which also didn't help. The only way to get it working was to restart. No huge deal, but I'm trying to figure out an easier way to reboot the wifi without restarting. And I'd also love to know what's going on when this happens?