|Whichever way you decide to connect the two routers (wired or wirelessly) you will have to change the LAN configuration on one of the two routers. You would want them both on the same subnet so all LAN devices could communicate. |
If you click on my name above and read my "how-to" guide on adding a second router the "LAN port to LAN port" scenario is the one you'll want to use if you interconnect the two routers with a network cable (the easiest solution).
In your case however, since you have two separate providers, you'd want to shut off DHCP on the downstream router and statically assign TCP/IP settings to those clients you wish to have use that as their internet connection.
With the upstream router having an IP like: 192.168.0.1 and your downstream: 192.168.0.2, you would just have to be sure all clients you want using .2 as their internet connection have that IP address (192.168.0.2) statically assigned as their Default Gateway IP, along with their IP and subnet mask.
For the sake of clarity, here's how I'd do it.
Router 1 (provider 1)
DHCP Scope: 192.168.0.100 to 192.168.0.199
Router 2 (provider 2)
(Connected from LAN port on router 2 to a LAN port on router 1 as well as the external connection to the internet that plugs in to the WAN port on this router)
All clients on router 2 have their IP settings statically assigned using IP's not in the DHCP scope. Also, for obvious reasons, do not use .1 or .2
The default gateway for clients connected to router 2 would be 192.168.0.2
All other clients would get their TCP/IP settings from the DHCP server on router 1 and those would include Default Gateway IP: 192.168.0.1
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.