Here's a pic of the setup I wanted to accomplish. It's similar to the first line except that my DIR-655 is wirelessly bridged to the WNR3500 and the WNR3500 acts as the vpn endpoint. (if you dont have a dd-wrt capable router then youll have to use a computer or another device as the vpn endpoint)
Here's some links for reference to get you familiar:
1. Wireless Bridge
http://www.dd-wrt.com/wiki/index.php/Wireless_Bridge2. Repeater Bridge
http://www.dd-wrt.com/wiki/index.php/Repeater_Bridge3. Configuring PPTP VPN
http://www.hanselman.com/blog/ConfiguringPPTPVPNWithAlternateLinksysRouterFirmware.aspx4. VPN Pass-through not working on D-Link DI-524 - Networking
http://fixunix.com/networking/37500-vpn-pass-through-not-working-d-link-di-524-a.html Here's how I did it. (refer to links 1 & 2) I set my DIR-655 ip as 192.168.1.1 (you could set this to whatever you want), which will also be the default gateway address. Setup your DDNS service and anything else. For the wireless side you have to pick a specific wireless channel, channel width, encryption type, SSID and password, etc.
On the dd-wrt router (refer again to links 1, 2 & 3) set router address to 192.168.1.2 with the default gateway the ip address from the first router which was 192.168.1.1. On the wireless side while the router is in AP mode, setup the specific wireless channel, channel width, encryption type, SSID and password, etc exactly as the host AP. Setup your DDNS service if you wish (although I dont think it matters since the host router is setup with ddns already plus the ddns updates dont occur to the second router as it seems to not work going from wan to wireless lan). Under VPN the server ip will be the IP address of dd-wrt router since its hosting the VPN endpoint. For me it was 192.168.1.2 finally change it client bridge and save and apply settings.
Back to the hosting router the DIR-655. (refer to link 4) Youll need to forward ports or create virtual servers to allow the vpn traffic to come through. I chose the virtual server route as mentioned in the link.
on my router dir-655, you will need to set this in the virtual server list...
Gre:
Under traffic type, the protocol is "Other", and set to 4. The public and private field should greyed out. Ip, is ip to your server or vpn endpoint. For my case it was 192.168.1.2
pptp:
Under traffic type, the protocol is "TCP", and set to 6. The public and private field is set to 1723. Ip, is ip to your server or vpn endpoint.
Make sure your software firewall allows this. (you can disable it)
Make sure in the ALG section that pptp is checked. (all the options there should be already checked by default)
If everything is setup successfully youll should be able to create and connect to a vpn connection successfully (refer to link 3) In addition to this I have full access to both routers. I can type the ip address of either router and get to the router page successfully. I can also remote manage the routers as well.