C3700 with Home Security System

So I just got my new C3700 Gateway. I also just recently purchased a home security system. When setting up the NVR box for the security system, it needs to be connected to WAN through an ethernet cable. My C3700 is being used for general WIFI for my house. But I would also like to hook up my home security system as well. However the C3700 only has to inputs for LAN. Is there anything I can do to connect my NVR box without interupting my existing home WIFI?