How do I separate two routers from a Home Network?

[portforwardingishard]

I've been trying to Port Forward a few games, but I've got two routers connected to each other and I don't know how to separate them. I was not the one who set them up and I lack knowledge in this subject, so please try to be simple with explanations. I've tried doing the DMZ thing and following tutorials to Port Forward with two routers, but I got an error when trying to forward an external link. I have a Static IP address and I'm using two TP-Link routers (Both TL-WR841N).

 

[kanewolf]

The "second" router, it the purpose is to provide WIFI should be configured as an access point rather than a router. Here is the sticky to convert -- http://www.tomshardware.com/forum/36406-43-convert-wireless-router-wireless-access-point

If you have the second router as an access point then you won't have to port forward through it.

 

[portforwardingishard]

The "second" router, it the purpose is to provide WIFI should be configured as an access point rather than a router. Here is the sticky to convert -- http://www.tomshardware.com/forum/36406-43-convert-wireless-router-wireless-access-point

If you have the second router as an access point then you won't have to port forward through it.

Actually, I forgot to mention something. The modem is somewhere else, and it isn't any of the two routers, but for some reason, it isn't detected by the Port Forward Network Utilities, or anything else (like cmd commands like ipconfig /all) and I don't know why. Also, it's connected to the two routers, so does this make them both access points since when the modem is off, none of the routers work? If yes, should I just go to the modem and port forward from it?
Also, all the link's steps did was making my internet stop working until I changed the settings back to normal.

 

[kanewolf]

You will have to post a drawing of the connectivity and a list of all the model numbers of the devices. I can't figure out what is connected to what from a description. Here is a sticky on how to post images -- http://www.tomshardware.com/faq/id-2580030/detailed-instructions-posting-images-tom-hardware.html

 

[failboat]

public ip/WAN interface router1----port forward or "DMZ host"-> LAN ip / WAN interface router 2---port forward-->LAN ip of client

made up example
public ip 8.8.8.8
fixed lease DHCP on router 1: 192.168.1.2 (router2 only client)
fixed lease DHCP on router 2: 192.168.2.2 (end target for service)

router 1 set DMZ host 192.168.1.2
router 2 port forward service ports to 192.168.2.2
connect to service 8.8.8.8: port

I only recommend using "DMZ Host" to another router. It's generally not a good feature to use on a client. Use port forwarding for the client. If you're trying to open this service to just a few people you can configure the inbound rules to only allow those specific source ips. Then random people can't scan your services and try to connect. Use a strong pw on any service allowing inbound.