1. Introduction to the Cisco IOS
Chapter 4
Introduction to the Cisco IOS

2. Cisco Internetwork Operating System (IOS)
Most Cisco stuff runs on same OS
Uses command line interface (CLI)
Handles protocols and functions
Controls security
Scaleable
Reliable

3. Connecting to a Cisco Router
Configure router, verify configuration, check statistics
Three ways to connect:
Console port, often used first to set up router (RJ-45 jack)
Auxiliary port for modem access (RJ-45)
Telnet to any active interface
Serial interfaces for WANs, AUI for Ethernet

4. 2501 Router

5. Bringing up a Router Power on self-test (POST)
Then, loads Cisco IOS from flash memory
Flash memory is electronically erasable programmable read only memory (EEPROM)
IOS loads and looks for startup-config file in nonvolatile RAM (NVRAM)
No startup-config? Then router enters setup mode for you to configure it

6. Setup Mode
Basic Management Setup to get the thing started and allow connectivity
Extended Setup to configure global parameters and each interface
Defaults are provided in [ ]
Or, use Command-Line Interface
Don’t enter the initial configuration dialog
Router then checks all interfaces
Router then sits at prompt and waits for you

7. Passwords Can Be Confusing
enable secret is password to get into configurations
enable password is older version, you can set it and not use it ever again if enable secret is set
virtual terminal password is used when telnetting to router (must have one before telnet is allowed)

8. The Interfaces Can set: Router then displays your settings
duplex mode
IP address
Subnet mask
Router then displays your settings
Choosing not to configure during bootup brings you to CLI

9. Logging into the Router
User mode:
Router>
Used mostly to view statistics
Router> logout exits
Router> enable enters privileged mode
Privileged mode:
Router#
Used to view & change router configuration
Router# disable goes back to user mode
Router# logout exits

10. Overview of Router Modes
Global changes:
config terminal or config t
Changes made to running-config (DRAM)
To change the startup-config (NVRAM)
config memory or config mem
Note: Any configuration changes need to be placed into RAM. Typing config mem or config net (from a TFTP host) will replace the current running-config

11. Configuration and CLI Prompts
Global configuration prompt
Router(config)#
Interfaces
Router(config-if)#
Sub-interfaces
Router(config-subif)#
Line Commands
Router(config-line)#
Routing Protocol Configurations
Router(config-router)#

12. Editing & Help Features

13. Editing & Help Features
Commands starting with a certain letter
Router#c?
clear clock configure connect copy
Router# clock ? shows next options for clock
Enhanced editing commands on pp
Router-command history shows recent commands used (p. 162)
show history (last 10 commands)
Gathering Basic Routing Information
show version

14. Hands-On Labs
Pages

15. Setting the Passwords 5 passwords:
1st two used to set your enable password
Used to secure privileged mode; Router>enable
Other three are used to configure a password in user mode via:
console port
auxiliary port
Telnet

16. Passwords Enable passwords Auxiliary password Console password
Router(config)#enable password cisco
Router(config)#enable secret cisco
Auxiliary password
Console password
Telnet Password (must be set before telnet allowed)
Router# sh run will display passwords! To encrypt:
Router(config)#service password-encryption

17. Hands-On Labs
Pages

18. Banners Users & admins see them when logging in Types
exec
incoming
login
Message of the day (motd) is most common, displays for all users arriving on any port
Notice delimiting character

19. Router Interfaces
Routers have interfaces to connect networks: serial, ethernet, fast ethernet
How to set interfaces?
Router# show int e0 lets you check check status of Ethernet interface
Router# config t enters configuration mode
Router(config)# int e0 to work with Ethernet interface
Router(config-if)# no shutdown brings it up
Router(config-if)# shutdown takes it down

20. Setting IP Address Configuring an IP address on an interface:
Router(config)#int e0
Router(config-if)#ip address
Router(config-if)#no shut

21. Serial Interfaces
Serial interfaces usually are DTE and connect to CSU/DSU, which is the DCE
CSU/DSU usually provides the clocking
In a lab, one router will be DTE and the other will be DCE
Router(config)# int s0
Router(config-if)# clock rate 64000
Clock rate is in bits per second
Set bandwidth for routing protocols to use:
Router(config-if)# bandwidth 64
Bandwidth is in KB per second

22. Hostnames & Descriptions
Hostnames locally significant (not used as network name)
Router(config)# hostname todd
todd(config)#
Descriptions can make printouts easier to read (see page 205)
Atlanta(config)# int e0
Atlanta(config-if)# description Sales Lan

23. Viewing, & Saving Configurations
running-config saved in DRAM
startup-config saved in NVRAM
Router# copy run start
Router# sh run
Router# sh start
Router# erase startup-config

24. Verifying Your Configuration
Tools to check your config (pp ):
show running-config
show startup-config
ping an IP address
show cdp nei detail to find out IP addresses
trace to discover path through network
telnet to devices with IP addresses
sh interface to see one interface
sh int e0 sh int s1 (line up/down protocol up/down)
sh controllers s 0 (notice the space)

25. Hands-On Lab 4.5
Pages