|  |  | Overview
In "Router Configuration" you learned to use router modes and configuration methods to update a router's configuration file with current and prior versions of Cisco IOS software. In this chapter, you will learn to use a variety of Cisco IOS software source options, execute commands to load Cisco IOS software onto the router, maintain backup files, and upgrade Cisco IOS software. In addition, you will learn about the functions of the configuration register and how to determine what version of the file you have. This chapter also describes how to use a TFTP server as a software source. Multiple source options provide flexibility and fallback alternatives. Routers boot Cisco IOS software from: Flash memory TFTP server ROM (not full Cisco IOS software)