Cisco Systems CCNA 2 manual IOS file system overview, IOS naming convention

5.2.1 IOS file system overview

A router or switch requires software to operate. The following are two basic types of essential software:

•The operating system

•The config file

The operating system that is used in almost all Cisco devices is the Cisco IOS. The IOS is the software that allows the hardware to function as a router or a switch. The software a router or switch uses is referred to as the configuration, or config file. The configuration file contains the instructions that define how the device will route or switch.

The IOS is stored in Flash memory. The configuration file is stored in NVRAM. Discuss with the students the differences between these types of memory and help the student understand by opening a router and showing the inside of the router to the students. Discuss RAM, ROM, flash, and NVRAM. Students must understand the differences between them. One difference to discuss is that the IOS in flash or RAM is several megabytes and the configuration file in NVRAM is up to a few kilobytes.

Version 12 and newer releases of the IOS provide a single interface to all file systems. This is referred to as the Cisco IOS File System (IFS). The IFS can be used to perform all the file system management for a router. Explain that the IFS is based on UNIX file systems.

5.2.2 IOS naming convention

Many different versions of the IOS are available. The IOS supports many different hardware platforms and features. This is a continuous development process.

To identify the different versions, Cisco has a naming convention for the IOS files. The IOS naming convention uses different fields in the name such as hardware platform identification, feature set identification, and the numerical release.

The first part of the IOS filename identifies the hardware platform. The second part of the IOS filename identifies the various features that the file contains. The third part of the filename indicates the file format. It specifies if the IOS is stored in flash, if it is in compressed format, and if it can be released. The fourth part of the filename identifies the IOS release.

This is an important concept for students to understand. They should be able to look at an IOS filename and determine the hardware platform, features, file format, and the release. Students should also understand that these naming conventions vary for different releases. This occurs as the feature sets are rebundled and renamed.

Show students some of the tools for IOS planning that are available on the Cisco website. Most of these are only available to users who have obtained user ids through SmartNet.

http://www.cisco.com/warp/customer/620/1.html

http://www.cisco.com/en/US/customer/products/sw/iosswrel/ios_abcs_ios_networking_the_ent erprise0900aecd800a4e14.html

55 - 238 CCNA 2: Routers and Routing Basics v3.1 Instructor Guide – Module 5 Copyright ♥ 2004, Cisco Systems, Inc.