From LQWiki

A router is a networking device which operates at layer 3 of the OSI Model. Its purpose is to switch data packets between its various interfaces based upon the destination IP address of the packet.

Routers are intelligent devices and can make decisions about which route a packet can take through a network if there are multiple paths possible. The decision about which path to take is made from a link's cost which is calculated from the factors of bandwidth, hop count, financial cost, load, delay and reliability.

Most Linux distributions come with routing support allowing your Linux machine to operate as a router if it has one or more NIC installed.

Many routers also provide a service known as Network Address Translation or NAT.

It should also be pointed out that from a security point of view, if you have a router, then every computer behind it is protected from attack from the other side (i.e. the internet). This doesn't protect you from someone sending you a trojan through email, if you run the attachment however, but it will protect you from worms running around on the internet. Linux of course does not have anything like the kind of problems with worms and trojans that windows has though.

See also

• Guide to setting up IP routing.

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