We have an office (1 of 20) that has a site-to-site VPN to our corporate HQ (like all offices do). The office has a Sonicwall TX170 (like all offices do) and HQ has a Sonicwall pro 2040. For the last few weeks, the office VPN has been working intermittently. It was working fine for many months before that. No recent changes have been made to either Sonicwall that we know if. After some troubleshooting, we found that if we disable the wireless on the office Sonicwall, then the VPN is stable. But our offices need the wireless connectivity.
We've tried playing with the advanced wireless settings DTIM Interval, RTS Threshold, Fragmentation Threshold, etc. with no luck. But we are not real clear on what those settings should be or if they would help in this situation.