Verizon FIOS setup Walkaround with Coax cable (MoCA)
From DD-WRT Wiki
 Verizon Fios setup Walkaround with Coax cable (MoCA)
This is a walkaround for Verizon Fios setup if you already have Fios installed with an Actiontec Router MI424WR (AT) connected by coax cable (MoCA).
1.- First thing you should do is go into the AT setup by the router's IP usually 192.168.1.1 . Enter the or your Username and Password (defaults: admin and password/password1).
2.- Turn off the wireless by going to Wireless Settings, then Basic Security Settings turning wireless Off then hit Apply. Now that this is done, unplug the power cord from your AT.
3.- Now configure your dd-wrt router into AP mode and change the IP address from 192.168.1.1 to for example: 192.168.0.1 . After doing this unplug the power from dd-wrt router. Then take an ethernet cable plug into a LAN port of the dd-wrt router to your PC.
4.- Now take another ethernet cable and plug it into a WAN port from the dd-wrt router to a LAN port on the AT.
5.- Last power both routers on, the AT first and then the dd-wrt router. TADA!!!! Now you have a secondary router and can connect to the internet through it. If you have Fios TV, VOD and Widgets will still work with this setup. And I believe you will have Verizon support for AT configuration.
NOTE: You should have your WAN Connection type to Automatic Configuration-DHCP on the dd-wrt router. Meaning that it will hand out the IP addresses automatically.
NOTE: If you want your dd-wrt router as the Primary router, it is best to get Verizon to turn Ethernet on at the ONT and run a cable to you PC.
From here you can just log into the web GUI of the dd-wrt router from the address that you used (192.168.0.1) and set it up however you like. To change any settings in your Verizon AT router you still just use the default IP address 192.168.1.1 .
If you want or have Verizon Fios with Ethernet instead of coax cable (MoCA) connected read this Tutorial, http://www.dd-wrt.com/wiki/index.php/Verizon_FIOS_setup_with_dd-wrt_as_primary_router