We have a 2920 (f/w 3.6.3) which randomly (sometimes once a month) seems to cause internet connection problems.
When it gets into this state pinging IPs works fine but requesting a DNS lookup times-out. Stuff with pre-established connections will continue to work (and stuff where the IP has presumably already been retrieved and cached works fine too) but anything that requires a DNS lookup to get started will fail.
Rebooting the router immediately resolves the issue for some random amount of time.
I've tried:
* Factory Reset
* Swapping for another identical router
* Changing the internet connection its connected to (we've tried ADSL modem, cable modem & we are now on fibre leased line - all the same)
* Setting router to reboot early in the morning, once a day
No joy! Can't figure out what is going on here. Any troubleshooting suggestions?