I have three locations all using the R600VPN for firewall. All VPN Site-To-Site connections were up this morning. This is what I have:

Site A

Site B

Site C

Site A has a VPN to Sites B and C

Site B has a VPN to Sites A and C

Site C has a VPN to Sites A and B

  I am at site A working through the VPN to site C. I notice the VPN drops. Usually not a big deal as if it happened in the past, the connection restored in seconds without further issue. But this one is not restoring. I look at site A R600 log and see that the connection is just restored and go to VPN/IPSec, IPSec SA page and it reports the SPI. But still no connection to any client at Site C. So, I go back to the logs and notice the Site A <-> C connection keeps dropping and reconnecting. I first assumed Site C has an internet connection problem.

  From site A, I can log into Site B without problems. This tells me Site A does not have an internet problem. From Site B I can connect to clients at Site A, obviously, and the there is also no problem connecting from Site B to C!! Sites A and B have the same ISP. Site C has a different ISP. From Site B, I connect to a client at Site C and verify that Site C does not have a problem with the internet, but also confirm that I cannot access any clients from Site C to Site A. I also verify that I can connect back to Site B clients from Site C.

  I rebooted Site C R600 but no help. I cannot reboot Site A R600 at this time as I would hate to loose the Sites A <-> B VPN connection.

  Sometimes I would like to throw these devices out, but we have these because I pushed for them.

  What could be causing this?

More info: I have disabled/enabled the VPN connection from both Sites A and C. No help.