Cisco 2501 - Router - EN Bedienungsanleitung PDF herunterladen (Seite 6)

184

Chapter 4

Introduction to the Cisco IOS and SDM

As a heads up, I'm going to be using all new 2800, 1800, and 800 series routers throughout

this book to demonstrate examples of router configurations. But understand that you can use

the 2600 and even 2500 routers to practice routing principles.

You can find more information about all Cisco routers at

www.cisco.com/en/

US/products/hw/routers/index.html

Bringing Up a Router

When you first bring up a Cisco router, it will run a power-on self-test (POST). If it passes,

it will then look for and load the Cisco IOS from flash memory—if an IOS file is present.

(Just in case you don’t know, flash memory is electronically erasable programmable read-only

memory—an EEPROM.) After that, the IOS loads and looks for a valid configuration—the

startup-config—that’s stored in nonvolatile RAM, or NVRAM.

The following messages appear when you first boot or reload a router (I am using my

2811 router):

System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Initializing memory for ECC

c2811 platform with 262144 Kbytes of main memory

Main memory is configured to 64 bit mode with ECC enabled

Upgrade ROMMON initialized

program load complete, entry point: 0x8000f000, size: 0xcb80

This is the first part of the router boot process output. It’s information about the bootstrap

program that first runs the POST. It then tells the router how to load, which by default is to

find the IOS in flash memory. It also lists the amount of RAM in the router.

The next part shows us that the IOS is being decompressed into RAM:

program load complete, entry point: 0x8000f000, size: 0x14b45f8

Self decompressing the image :

####################################################################

############################################ [OK]

The pound signs are telling us that the IOS is being loaded into RAM. After it is decom-

pressed into RAM, the IOS is loaded and starts running the router, as shown below. Notice

that the IOS version is stated as advanced security version 12.4(12):

[some output cut]

Cisco IOS Software, 2800 Software (C2800NM-ADVSECURITYK9-M), Version

12.4(12), RELEASE SOFTWARE (fc1)

47020.book Page 184 Wednesday, January 2, 2008 4:31 PM

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