What's the difference between a gateway and a router?

A gateway connects two different networks, while a router directs data traffic within or between networks.

A gateway is a node in a computer network that serves as an access point to another network, often involving not only a change of addressing, but also a different networking technology. For example, a local area network (LAN) that uses IP addressing may be connected to a wide area network (WAN) that uses a different addressing scheme, and the gateway is the device that facilitates this connection and translation. Gateways can operate at any layer of the OSI model, but they are typically associated with the network layer. They can perform more complex tasks than routers, such as protocol translation and data encryption/decryption.

On the other hand, a router is a device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node. Routers operate at the network layer (Layer 3) of the OSI model and use IP addresses to determine the most efficient path for forwarding the packets.

While both gateways and routers are essential for directing network traffic, they serve different purposes. A router connects devices within a network by forwarding data packets between them. This can be within a small home network or within a large corporate network. A gateway, however, is more complex and serves as the 'door' between two networks, often involving a change in addressing or protocols.

In summary, while routers and gateways both help direct network traffic, they do so in different ways and in different contexts. Routers are primarily used to connect devices within a network, while gateways serve as the connection point between two different networks.