The main functions of the router include connecting to the network, assigning IP addresses, realizing network security, data flow control and wireless network connection.  ‌‌A router is a hardware device that connects two or more networks and works at the network layer as a gateway.  It can query the routing table and routing protocol to find the best transmission path for the received packets, and then forward the packets from the corresponding interface to the destination address

Routers can provide connections within the enterprise, between the enterprise and the Internet, or between Internet Service Provider (ISP) networks.  The largest routers interconnect various ISPs or may be used in large corporate networks.  Smaller routers usually provide connections for typical home and office networks.  Different types of routers can be used for different needs.