iptables question

[deloptes]

Hi,
I need some help and I'll appreciate it.

I have a firewall with iptables behind the modem.
on this firewall I have 
        eth0 with ip 10..1 to the modem ip: 10..12
        eth1 with ip 192..1 to the intranet

iptables is doing SNAT from 192..1 to 10..1

I wonder how I can ssh from 192..NN to 10..NN
What magic should I apply to make it happen?

Thanks in advance