Windows 2008 / 2012 server environment running AD. Internet via Smoothwall proxy and BT SFBB (both of which tested and working OK). All been working but all internet connectivity now lost. No obvious reason behind this. Both servers report "limited connectivity" or "no internet". Windows 2008 had been trying to install updates around time internet was lost, but history shows no updates actually deployed.
Can ping internal addresses but timed out when try to ping any external addresses (trying with both name or IP address).
Possible DNS issue occurred? Where should I start?
Thanks in advance for any recommendations.