I do have a problem with a client system using Cisco VPN client behind
m0n0wall. Apparently there are different settings on the Cisco Concentrator
that change the way the VPN connection is established.
I have 3 different VPN entries in the Cisco client, two of which work just
fine behind m0n0wall, whereas the 3rd one only works without the firewall.
Looking at the firewall log, it seems that the VPN Concentrator is trying
to connect to the client on port 500/UDP, which fails, of course.
Maybe some kind of VPN client detection could be integrated, which
automatically detects internal VPN clients trying to establish VPN
sessions, and then allows the separate connection back in to go through?