iptables - vpn - bridge mode - complex

[karillion () gmail com]

Hi All,

You will have to forgive my complete noobishness on this but here it is.

I am responsible for setting up a vpn to connect our Sydney office to our NZ office, we have just purchased 2 new 
linksys routers both RV082's.

the current topology consists of a cisco 2514 at the sydney office and a linux firewall at the NZ end running iptables 
on debian.

The plan is to place one of the linksys routers at either end behind each router respectively. so it would go 
Sydney_RV082-cisco_2514---Debian_firewall_iptables-NZ_RV082.

we are getting connectivity either way fine, i can ping from the Sydney_RV082 to the NZ_RV082 find both ways, but upon 
attempting to connect the VPN, it just wont establish a connection.

i have come to supect that the cause of this is that the iptables firewall is port forwarding the ip from the NZ 
linksys router.

my proposed solution is that we activate a bridging mode on the iptables firewall so that it just passes through the 
connection from the outside to the linksys.

heres where things get interesting.

the iptables firewall is shared AND is not managed by me.

so im confident in getting the iptables firewall to use bridge mode but the thing is i need it to bridge ONLY traffic 
headed for a specific ip address (the rv082)

now if i can get it to do this i THINK this will solve my problem and get the vpn to connect so here is my full 
wish-list.

1. Can i do this with iptables?
2. If i can, will this solve my problem?
3. What do i set the default gateway to on the NZ RV082... whereas it is currently set to the ip bound to internal side 
of the iptables firewall
4. Is there a better way to go about this?

Thanks for any help on this, i need this solved in the next couple of days so ANY helpful feedback would be really 
appreciated.

Cheers,

Ludi