I have been attempting to connect a Verizon 4G LTE USB551L to a RT-N66U. I have looked all over the interwebs, but found no encouraging info. I was successful using Asus latest build 22.214.171.124.270. The Modem was setup, and it worked good in a Cradlepoint MBR-900, and ZVW access. After trying a bunch of settings in the RT-N66U, and messing it up. I was finally successful with the following settings: Enable USB Modem Yes Location USA ISP Verizon APN service VZWINTERNET Dial Number *99***3# PIN code Username Password USB Adapter Auto All other fields were left blank. Reboot, and it works great. Up to 22 Mbps downloads. Speed is between 9Mbps and 22. I will now flash back to Merlin build, Tomato, and report back in this thread.