by second subnet do you mean like a second network? Because i am. I want to have Network a in the house with the Extreme and Network b in the garage with the router.
Yes, by a second subnet I do mean a second network. In your configuration, you will have two routers in series. If both have NAT & DHCP enabled, network clients connected to either can still access the Internet, but they won't be able to access clients on the other network.
And how exactly should the connections be from the Extreme to the router because right now i cant even connect to the router in the garage to change the settings.
Is the other router another AirPort or some other manufacturer's product? Regardless, if it will have NAT enabled, then you want an Ethernet cable going from one of the available LAN ports on the AEBSn to the WAN (or Internet) port on this other router. This other router would also be getting a Private IP address to its WAN port that is being provided by the AEBSn and NOT a Public IP address from the ISP.
When you have multiple routers downstream, you will want them to have static IP addresses so that they can always be "found." Again, since this other router will be downstream of the AEBSn, you will want to set its static IP to be just outside of the range of the AEBSn's DHCP server. The AEBSn's default range is: 10.0.1.2 - 10.0.1.200 ... so setting the IP address of this other router to 10.0.1.201 should be fine.
