Deep Inspection Breaking Web Browsing (and more!)
I just wanted to put some feelers out to see if anyone else has seen this problem and might know the solution. We've been working with Fortinet for several weeks now and haven't gotten anywhere.
We've been running into an issue with a small subset of our clients where all web browsing breaks (websites time out) after 1-3 weeks of uptime on the firewall. Generally, toggling from deep inspection to cert inspection will get them going again, but we've also found through process of elimination that disabling Web Filtering and AV will also get them going. If we let the firewall run in this manner for another day or two, eventually the IPsec VPNs will drop and nothing we can do will bring them back up. The GUI will also become inaccessible (login page won't even load) at this time. CPU and memory are both very low throughout the whole process, so conserve mode does not appear to be a factor. Rebooting the unit will bring everything back up, and we can re-enable full UTM without issue for another 2-3 weeks before the process starts all over again.
So far this problem has presented itself with Fortigate 100E and Fortigate 80E models. The 60E and 200E models we have deployed are all working perfectly with the same base config. Firmware versions range from 5.6.2 to 6.0.4 and upgrading has not yielded any positive results.