IOS Images and Configuration Files

Eventually you will want to upgrade your router's software. The IOS (Internetwork Operating System) is the software that resides inside the Cisco device. Upgrading IOS involves transferring a new IOS image to your router from some kind of server. As we'll see in this chapter, there are several methods for uploading a new IOS image: the most common include using Trivial File Transfer Protocol (TFTP), Remote Copy Protocol (RCP), or Secure Copy Protocol (SCP). Before we discuss how to transfer a new image, let's define exactly what is meant by an "image file" and how it differs from a configuration file.

IOS image files contain the system code that your router uses to function, that is, the image contains the IOS itself, plus various feature sets (optional features or router-specific features). However, the features are not configured in any way. The router's actual configurationwhich features are enabled and how they are used in your particular network environmentis stored in a configuration file written in IOS's configuration language. The commands in this file describe everything from the router's name and the IP address of each interface to the protocols that you're using, address translation, security, and more. The router is useless without a concrete configurationjust like an operating system kernel is useless without the configuration files (such as the Windows registry or the files in /etc on a Unix system) that tell the kernel how you want it to operate in a particular situation.

Getting Started

IOS Images and Configuration Files

Basic Router Configuration

Line Commands

Interface Commands

Networking Technologies

Access Lists

IP Routing Topics

Interior Routing Protocols

Border Gateway Protocol

Quality of Service

Dial-on-Demand Routing

Specialized Networking Topics

Switches and VLANs

Router Security

Troubleshooting and Logging

Quick Reference

Appendix A Network Basics


Cisco IOS in a Nutshell
Cisco IOS in a Nutshell (In a Nutshell (OReilly))
ISBN: 0596008694
EAN: 2147483647
Year: 2006
Pages: 1031
Authors: James Boney © 2008-2020.
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