I have been struggling with this since we got it all installed. We recently got cable TV from Wave cable, and they gave us An ARRIS setup. Including this *Lovely* MG5225G/NA gateway, the gateway is what is giving me the troubles. We have a linksys e2500 router connected through the gateway, and all of our devices connected through the router. I have been going back and forth with the router and gateway trying to get ports to work, And they worked fine back when i was just using a modem to connect to the router. Between me and my friends i am the one that host all of our servers, Killing floor, mine craft, hamachi LAN parties, and so on. Since this setup was installed i have been unable to get any ports to work and am in need of desperate help. Also when connecting to the gateway via chrome with 192.168.0.1 the interface allows me to search through the tabs, but it wont let me change any settings. When i hit apply to the settings it does nothing and reverts them when i refresh the page.
Have you considered removing the router (Linksys) and just using the gateway? The Arris should be able to do all that you need without the added complexity of using a second router.
I have thought of doing that, but when connecting to it through its ip, it seems to never let me change anything, and if i do get something to change, it resets, and in order to get it to work again i have to unplug its power for 10 seconds and plug it back in or it will remain inoperable. The biggest reason i am hesitant to do so is that me and my brother would have to rewire under the house again, which is a real pain the the ass. But if that is the best option i can do that.
I would recommend you consider this. Go with a single router. If you need to make any changes in wiring to physically connect devices after the second router is removed, then just use a small switch (like the one below) to serve as that bridge (where the router would have been). No need to rewire.
If the Arris is giving you problems, have your ISP fix/update or replace it.
If you really want to stick with the 2 router approach, you can. I would recommend the following if this is the plan:
1. Disable the wireless connection on the Arris (only use the Linksys)
2. Don't connect any devices to the Arris, except for the Linksys (connect the WAN port to one of the available ethernet ports on the Arris).
3. Use the Linksys to provide all networking connections (wired and wireless) to your connected devices (make sure to use a different network segment than assigned by the Arris. If the Arris assigns 192.168.1.x, then use 192.168.2.x on the Linksys and assign DHCP clients from that pool).
4. You will have to figure out how to open ports on the Arris to allow external access for users to connect to your game servers.
Note: These things are intended to simplify your internal network to not have 2 separate network segments (Arris and Linksys managed). It also helps to explain why a single router is preferred. Additional networking devices can actually make your overall network slower as there are more "moving parts".