We recently put a SA520 at a data center and a SA520W at an office and created an IPSEC VPN tunnel between the two. We then added a configuration for remote users using the QuickVPN client (very unhappy no 64 bit or Win 7 support).
Now that we've begun testing we've observed that as soon as anyone uses the VPN tunnel, the latency jumps from 12-16ms to 120-240ms and stays there for about 15-30 seconds.
Once we observed that, we started doing ping tests from the outside. For some reason both routers drop nearly all the ping requests and actually respond about 1 in every 50 pings. I've ensured that all the firewall items are turned off and that fact that it will respond every now and then tells me something is up.
I then tested using a VNC connection behind the device at the data center. The connection stays open until about 3-7 minutes in and the connection drops or hangs while it tries to refresh (dropped packets). I have no issues with any other routers or equipments on the same subnet, in the same rack. I'd blame one router being bad if it wasn't for the fact that I see the issue on both routers, at two different sites, on two different ISPs.
I've called the small business support line and they have no idea what to troubleshoot other than maybe changing the MTU settings. They've escalated the issue to a team in California but apparently escalation only means someone else will contact me within 48 hours (seriously?!?!?!).
As I'm at wits end, that's why I'm trying all options such as posting here. Anyone else observed similar behaviour?