I need to separate wireless network we have for customers from our network. We have our network on ADSL router Netgear DGN2200 (192.168.0.1/24) which is dishing out DHCP and doing DNS. Computers are in Workgroup > we don't have machine with server operating system. We also have additional router WNR2200 which is plugged into the DGN2200 network and is getting IP address for its WAN port. WNR2200 has got different local subnet 172.16.16.0 with 255.255.0.0. WNR's IP address is 192.168.1.2 with 255.255.255.252 while DGN2200 gateway is 192.168.1.1 with 255.255.255.0. WNR2200 has wireless on it for customers and has DHCP and DNS enabled for its 172.16.16.0 network. I am not able to introduce VLAN because those routers don't support it.
The problem is that when connected to customers' wifi on WNR2200, I am able to ping and access all the devices on DGN2200's 192.168.0.0 network and obviously I don't want that.
I was wondering what's the best solution. I have researched a little bit and some people suggested getting another router in between DGN2200 and WNR2200. Additionally, I tried TP-LINK TL-WA901ND but it wouldn't sort out the problem.
Thank you for all suggestions.