I'm not that familiar with the inner workings of IPSec, but I think there might be a bug in the site-to-site vpn with a policy with compression enabled.
I've got my 7.902 box at home and a 7.504 box at my dads place. I've set up IPSec between them and if I enable compression in the policy on both sides I'm not able to ping the other side, but disabling it and I can ping.
See images of the policy settings on both sides. I've used the bottom one, where I have gone in and enabled/disabled compression on both sides to verify that the compression option stops the traffic.
Either it is a bug or perhaps there are a reason why compression isn't working/supported.
Both sides included in the tunnel is using private addresses (10.x.x.x 172.x.x.x)
See signature for hardware on both places.
