said by jza80:Thanks that worked! Magic! Is there documentation for the above commands? I would like to know more in case I need to troubleshoot things.
I suggest assigning the modem an IP address on a different subnet then the WRT54GL. Example: 192.168.25.1.
To access the modem, you need to use iptables. Login to the WRT and goto administration --> scripts --> firewall. Copy and paste the commands below into the window, then click save.
iptables -I POSTROUTING -t nat -o vlan1 -d 192.168.25.0/30 -j MASQUERADE
ip addr add 192.168.25.2/30 dev vlan1 brd +