Upgraded to Yosemite over the weekend and before the upgrade had I no issues with internet connectivity. After upgrading I noticed that I was unable to connect to the internet at home, but presumed it was a random issue and switched it off. On bringing my MacBook into my work I noticed that it would also not connect to the internet connection in work ether via both WiFi and cabled connections, though I could still connect to LAN devices.
The odd thing is that when using the System Recovery screen the internet connection appears to work fine as it was downloading the Yosemite image to reinstall it (though this kept failing because of too many people attempting to download the new release so was unable to attempt a reinstall) which makes me think its more of an issue something added to the recent OS upgrade.
Does anyone else have this issue, or know how to fix it?