I posted this at DSLReports.com and someone recommended asking in this forum. I have 2 brand new Linksys RV042 units doing a site-to-site VPN. Several times per day, traffic between the VPNs just..... stops. Neither side can ping the other over the VPN, although the public WAN IP still responds fine. (week-long ping monitoring to the public WAN IP at the other end, every 15 seconds, shows the WAN link is stable) When traffic stops flowing, BOTH gateway web interfaces still show the VPN as "Connected" status. The only solution is to manually force a Disconnect at one of the endpoints via the web interface. Then they immediately re-connect (like they're supposed to) and traffic starts to pass normally again. Firmware: Both are at the latest 1.3.9 and both have been re-flashed just in case the original onboard image was corrupt. Connections: One end is Road Runner, the other end is FIOS. To rule out a RR to FIOS routing issue, I unhooked the one from RR and took it to my next door neighbor who has FIOS, making a FIOS-to-FIOS VPN. Both endpoints are in the same city, about 8 milliseconds apart. Same result. After a random amount of time (sometimes 30 minutes, an hour, 2 hours, 3 hours...) traffic just stops passing, neither end can ping the other, even though the web interface shows "connected" at both ends. I've tried all combinations of enabling/disabling the Keep Alive feature, and the Dead Peer Detection feature, at one and both ends. No luck. Any advice to sort this out (other than sending them back for a refund and using a different brand)? Thanks in advance.