I have a NSA 240 in a central office with a site-to-site VPN to a branch office with a TZ-215. I setup the tunnel at both ends via the VPN wizard. Everything worked great for several months.
Today, it died, for no apparent reason. We have not had any ISP issues on either end and other tunnels stayed active.
When looking at the logs, I was getting lots of errors for NO_PROPOSAL_CHOSEN. According to fuzeqna.com, this indicates a mismatch in IKE proposals. However, non of that info changed, and indeed, both ends of the tunnel have the exact same proposal settings.
I was able to get it working for about 10 minutes by changing both ends from Group 2 to Group 5, but it has died again.
The tunnel has been up and running for over 3 months and today it's suddenly dying, any ideas?