I typically keep a few IPSec VPN connections open, using IPSecuritas. But when I turn on my Mac's Internet Sharing feature, to share my Ethernet connection over wi-fi, some of these stop working.
It doesn't happen 100% of the time, but it stops working as soon as I turn Internet Sharing on, and starts as soon as I turn it off. I'm testing this by pinging a host that's in the VPN's network, and watching when it becomes unreachable.
The Internet Sharing feature assigns IPs in the 10.0.2.x range. As far as I know, this range isn't being used by IPSecuritas. For example, one host that I can no longer reach is in the 10.13.x.x range.
I'm running OS 10.7.4, connected to the Internet via a cable modem and router. The router, a WRT110, has IPSec Passthrough enabled.
Any suggestions on how I can debug this?