i already buy the device.i use huawei e220 as my modem.my question is do i have to install the modem 1st or just connect to the router?
You should attached the huawei 220 first to the WAN port (USB port) of DIR-451 first. Then attach the RJ-45 UTP cable to LAN Port 1 of DIR-451 and then attach the other end of RJ-45 to the ethernet controller on your CPU. Plug the power adapter to the back of the DIR-451 then plug the other end of the power adapter to electric outlet. The router will initiate the initialization and internet connection process. That's all. Good luck.