Isolate an IP which is another router

[badgcoupe]

Hello all,
So I have a wndr3700 setup with Gargoyle. Everything is working great!

The only thing missing from the stock WNDR firmware is the guest wifi network. To get a guest network, I hooked up my old d-link 4300. Got that all working great but I would like to isolate anything that connects to the old d-link from seeing anything on the main network.

I did some searching and it looks like I could use iptables to do this? Problem is I am a complete noob when it comes to iptables and grasping how it all works is very difficult for me. Is there an easier way someone could help me out with?

Thanks much!

[badgcoupe]

I also found this article:
http://wiki.openwrt.org/doc/recipes/guest-wlan

Would this be as simple as SSH'ing into the router and modifying the files verbatim(except IP's) as shown in the examples?

[badgcoupe]

And one more thought...

Since the second router has a static IP could it just be placed in a DMZ?

[Kline]

If you are trying to provide a WLAN guest network with only default gateway (internet) access and no LAN access I imagine you could place your WLAN guest router on a separate network and then create a static route directing all of its traffic to the internet WAN link.

192.168.1.0 - Your private network
192.168.2.0 - WLAN guest network

(ISP) <-> WAN (RTR) LAN <-> WAN (WLAN)
Static route on (RTR) for all 192.168.2.0 traffic to strictly go out default gateway (to WAN).

Never had a need to setup a guest WLAN network myself, but in my mind this feels like it would work