Double NAT issues - FVS338

Hi,

I'm currently trying to use a FVS338 in a VPN gateway configuration to one of our provider companies. I've been given specific VPN and NAT settings that they require for the connection, however due to their IP scheme conflicting with ours, I must utilize double NAT on this connection.

Setup is as follows:

Site A (our network):

The tunnel is up, but I'm having trouble enabling the NAT on our end. I need hosts on Site A's local network to connect to 10.136.21.10, and have the firewall translate this address to the remote server x.x.58.10 at site B. The ADSL modem is also setup correctly to forward VPN traffic, and is working with a seperate VPN tunnel currently, so this can safely be discounted.

NAT requirements:

Site A to B: 10.136.21.10 -> x.x.241.229
Site B to A: x.x.241.229 -> 10.136.30.20

From what I can tell, you can configure NAT on the external interfaces without an issue, but I need to translate the address when it arrives on the LAN port (I think?).

I'd appreciate any assistance with this, please let me know if you need any clarification on the setup or requirements.

Cheers,

Mike