Traffic Cops of the Internet
We will only talk about Cisco routers, that is . . . since 99% of customers use that brand. Included are all of the basic Cisco router commands, along with descriptions of the interface.
Routers are the lynchpins of an IP network. They control the path that every packet takes from its original source to its final destination. The packets consist of bits (1's and 0's), and the all the bits in each packet are treated as a single unit by the router. In other words - a router routes packets of bits - not individual bits. It does receive and send data one bit at a time, but the routing intelligence relies on the structure of IP packets.
Here we will supply enough information to allow you to go to a customer site with a basic IP network - and configure or troubleshoot their routers. The more complex commands are omitted, and BGP concepts are not covered here (see the IP section for that)..