MANAGING CISCO IOS

By

Anil Kumar Vishwakarma

MCA,MCTS,CCNA

OVERVIEW

The router boot sequence

Locating IOS software

The configuration register

Recovering Passwords

Backing Up the Cisco IOS

Restoring or Upgrading the Cisco Router IOS

Backing Up Router Configuration

Restoring Router Configuration

Cisco Discovery Protocol (CDP)

ROUTER BOOT SEQUENCE 1. The router performs a POST. The POST tests the hardware to

verify that all components of the device are operational and present. For example, the POST checks for the different interfaces on the router. The POST is stored in and run from ROM (read-only memory)

2. The bootstrap looks for and loads the Cisco IOS software. The bootstrap is a program in ROM that is used to execute programs. The bootstrap program is responsible for finding where each IOS program is located and then loading the file. By default, the IOS software is loaded from flash memory in all Cisco routers.

3. The IOS software looks for a valid configuration file stored in NVRAM. This file is called startup-config and is only there if an administrator copies the running-config file into NVRAM.

4. If a startup-config file is in NVRAM, the router will load and run this file. The router is now operational. If a startup-config file is not in NVRAM, the router will start the setup-mode configuration upon bootup.

LOCATING IOS SOFTWARE

CONFIGURATION REGISTER It is 16-bit software register that’s written into NVRAM.

Used to control how the router boots up.

The default configuration setting on Cisco routers is 0x2102.

To know what is the current value of configuration register, use show version command.

You can change the default value by using this command.

Router(config)#config-register 0x2142

Notice that bit 6 can be used to ignore the NVRAM contents. If it is enabled.

RECOVERING PASSWORDS Here are the main steps to password recovery:

1. Interrupting the Router Boot Sequence by pressing the Ctrl+Break key combination when using HyperTerminal and while the router first reboots. The command prompt will be like that.

rommon 1 >

2. Changing the Configuration Register to ignore NVRAM contents by using this command

rommon 1 > confreg 0x2142

3. Reloading the Router and Entering Privileged Mode by this command

rommon 1 > reset

The router will reload and ask if you want to use setup mode answer NO.

4. Copy startup-config to running-config in Privileged Mode by using this command

Router#copy start run

RECOVERING PASSWORDS

5. Change password by setting new password

Router#conf t

Router(config)#enable secret kkkk

6. Change the value of configuration register to enable NVRAM

contents

Router(config)#config-register 0x2102

7. Save your work

Router#copy run start

8. Reload router to activate changing of configuration register

Router#reload

BACKING UP THE CISCO IOS

Before you upgrade or restore a Cisco IOS, you really should copy

the existing file to a TFTP or FTP host as a backup just in case the

new image crashes and burns.

To back up the Cisco IOS to a TFTP server, you use this command

Router#copy flash FTP OR

Router#copy flash TFTP

This command requires only the source filename and the IP address

of the TFTP or FTP server.

You can get the source filename by using Show flash command.

The key to success in this backup routine is to make sure that you’ve

got good, solid connectivity to the TFTP server. Check this by pinging

the device from the router.

Router#ping FTP_server

RESTORING OR UPGRADING ROUTER IOS

You can download the file from a TFTP or FTP server to flash memory

by this command

Router#copy FTP flash

This command requires the IP address of the FTP server and the name

of the file you want to download.

You are prompted to make sure that you really want to proceed with

erasing flash memory.

BACKING UP ROUTER CONFIGURATION

To copy the router’s configuration from a router to a FTP server, you can

use these commands.

Router#copy run FTP

Router#copy start FTP

Copying the Current Configuration to NVRAM

Router#copy run start

RESTORING ROUTER

CONFIGURATION

If you did copy the router’s configuration to a TFTP server

as a second backup, you can restore the configuration

Router#copy tftp run

This command ask you about FTP_IP address, Source

filename and destination filename.

CISCO DISCOVERY PROTOCOL CDP is a proprietary protocol designed by Cisco to help administrators

collect information about both locally attached and remote devices.

By using CDP, you can gather hardware and protocol information about

neighbor devices, which is useful info for troubleshooting and

documenting the network.

The show cdp command gives you information about two CDP global

parameters that can be configured on Cisco devices:

how often CDP packets are transmitted to all

active interfaces. CDP timer

the amount of time that the device will hold

packets received from neighbor devices. CDP holdtime

Router#sh cdp

Global CDP information:

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

Use the global commands cdp holdtime and cdp timer to configure the CDP holdtime and timer on a router:

Router(config)#cdp timer 90

Router(config)#cdp holdtime 240

Gathering Neighbor Information by using this command Router#sh cdp nei

Gathering Interface Traffic Information including the number of CDP packets sent and received and the errors with CDP.

Router#sh cdp traffic Gathering Port and Interface Information including CDP status on router

interfaces or switch ports.

Router#sh cdp interface To turn off CDP on one interface on a router,

Router(config)#int s0

Router(config-if)#no cdp enable

CISCO DISCOVERY PROTOCOL

(CDP)

Thank You