I have just recently switched to using a pix 501 from a Linksys RVS4000. Using the RVS4000, I was able to establish an IPSEC VPN through that fw, but I've been unable to get the configuration correct for the PIX 501. It is supposed to support IPSEC Passthrough to allow the VPN.
The Connection establishes but I don't get any response from the remote. Probably because of the NAT that is happening.
Is there a way to configure the 501 to allow two way communication using the VPN client behind it? BTW, I am connecting to another 501 in the remote location.