Set these up one at a time; when you've finished with the first 655, power it off and then set up the second.
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Turning a router into an AP.On the 1st DIR-655Set it up with the wizards included in the web interface
Set up any additional options you want (QoS, Port Forwarding, etc)
On the 2nd DIR-655Set the Router's IP address to one that is outside of the 1st 655's range (e.g. 192.168.0.50)
Disable DHCP/SPI/uPnp/Filters
Use the Wireless Network Wizard and set it up identically to the first 655. Channels needs to be different. SSID and PW can be the same.
Now take your Cat5 cable and plug it into port 1 of the first 655 and run it to port 1 of the second 655. Power both 655s up.
That should be it.
Remember if you want to make changes to Port Forwarding, Virtual Server, QoS, DHCP, Rules, MAC Address Fitering, Website Filtering, or any other changable feature,
do it on the first DIR-655 only.