1. CCNA 2 v3.1 Module 2

2. Module 2 Introduction to Routers
CCNA 2
Module 2
Introduction to Routers

3. Cisco IOS
Cisco Internetwork Operating System is the software that controls routing and switching functions of internetworking devices
Network services provided by Cisco IOS :
Basic routing and switching functions
Reliable and secure access to networked resources
Network scalability

4. User Router Interface
Cisco IOS software uses a command-line interface (CLI)
This environment is accessible through several methods.
Console session
Uses a low speed serial connection directly from a computer or terminal to the console connection on the router
No initial configuration necessary

5. Dialup connection:
Using a modem or null modem connected to the router AUX port.
No initial configuration necessary
Telnet session:
At least one interface must be configured with an IP address, and virtual terminal sessions must be configured for login and passwords.

6. Router user interface modes
CLI uses a hierarchical structure.
Entry into different modes to accomplish tasks
E.g., To configure a router interface, the user must enter interface configuration mode.
Command executive (EXEC): Validates and executes the entered commands.

7. IOS software separates the EXEC sessions into two access levels:
User EXEC mode
Privileged EXEC mode (enable)
User EXEC mode (view only)
Limited number of basic monitoring commands
To check and view the router status
Cannot change the configuration of the router
Prompt >

8. Privileged EXEC mode (enable mode)
Accesses all router commands
Configuration and management
To ensure authorized users access this mode
Configured it to require a password from the user before accessing it & User ID
Provides access to
Global configuration mode and others
Prompt #

9. Type enable to enter privileged exec mode
Type disable to enter privileged exec mode
Entering a question mark (?) at the privileged EXEC level will reveal many more command options than those available at the user EXEC level.

10. IOS Naming Conventions
Platform (Hardware): C1005
Features: “b”, Appletalk = 40 bit encryption
Format: F = Flash, M = RAM
Compression: Z = Zip compressed

11. Consideration when selecting a new IOS image
Compatibility with the router flash and RAM memory
i.e., is there enough space
To find this information use show version
router#show version
Displays the amount of available RAM
…cisco 1721 (68380) processor (revision C) with 3584K/512K bytes of memory.
3584k main memory
512k shared memory
router#show flash
Displays the amount of flash memory
… bytes total ( bytes free

12. Operation of Cisco IOS Software
The startup process of the router normally loads into RAM and executes one of three operating environments/ modes.
ROM monitor
Boot ROM
Cisco IOS
Systems administrator uses the configuration register setting to control the default start up mode for the router

13. ROM Monitor:
provides low-level functionality and diagnostics
used to
recover from system failures
recover a lost password
Can only be accessed by direct, physical connection through the console port
Prompt: ROMMON>
Boot ROM :
Prompt: Router(boot)>
Offers only limited IOS features
Used for flash image updates
copy tftp flash
copies an IOS image stored on a TFTP server into the flash memory of the router

14. Cisco IOS show version show flash Normal operating mode
Usually stored in Flash but run from RAM
Prompt: router>
show version
Displays
IOS image and version
Configuration register setting
Amount of available RAM
show flash
Displays the amount of flash memory
Used to verify that the system has sufficient memory to load a new Cisco IOS image

15. Initial startup of Cisco routers
If the router cannot find a configuration file, it enters “setup mode”. It is a basic configuration

16. Startup routines must accomplish 3 things
Make sure that the router hardware is tested and functional.
Find and load the Cisco IOS software
Flash, TFTP Server, ROM
Find and apply the startup configuration file or enter the setup mode
NVRAM, TFTP Server, Console

17. Router Startup Sequence
Powers up
Performs a power-on self test (POST)
Executes diagnostics from ROM to check all hardware modules
This verifies basic operation of CPU, memory, network interface ports
Software initialization
The boot field of the configuration register determines the location to be used in loading the IOS.
Flash (0X2102), TFTP Server, ROM
IOS Software is loaded
List of hardware and software is displayed on console screen
If valid configuration file exists
Configuration file from NVRAM is loaded into main memory
start routing processes, supply addresses for interfaces
If no valid configuration file exists
Operating system searches for TFTP server
If no TFTP server the setup dialog is initiated

18. Setup Mode
Entered only if configuration file cannot be found in NVRAM or TFTP
Permits administrator to enter minimal router configurations
Default answers appear in [ ]
Press Enter to use these defaults
Press Ctrl-C at any time
to terminate the process(setup mode)
all interfaces will be administratively shutdown

19. Router LED indicators
An interface LED indicates the activity of the corresponding interface.
A green OK LED indicates system is initialized correctly

20. Examining the initial router bootup Output
Output indicates a problem with the “NVRAM”. It could be “Write erased”

21. Router Output Tells Bootstrap version IOS version the router
Router model
Processor
Number of interfaces
Types of interfaces
Amount of NVRAM
Amount of flash memory

22. Logging into the router

23. Password commands to access privileged EXEC mode
When entering the Privilaged exec mode if the password: prompt is displayed, enter the password that has been set
Password commands to access privileged EXEC mode
Router(config)# Enable password <password>
Not encrypted
Router(config)#Enable secret <password>
Encrypted
Cannot be the same as enable password
Takes precedence over enable password

24. To return to the privileged mode type Ctrl Z.
From the Privileged mode you can enter the “Global Mode” & can configure the following;
Interface
Subinterface
Line
Router
Route-map
To return to the privileged mode type Ctrl Z.

25. Keyboard help in the router CLI
Typing a question mark (?) displays a handy list of available commands. (user or privileged modes)

26. “?” can also be used to complete incomplete commands
Eg .. Setting the router clock

28. The "^" symbol appears at the point in the command string where an incorrect command, keyword, or argument was entered.

29. Enhanced editing commands
“$” sign indicates that the command has scrolled onto the next line.

30. Router command history
The maximum number of commands held is 256.

31. The show version command
IOS version and descriptive information
Bootstrap ROM version
Boot ROM version
Router up time
Last restart method
System image file and location
Router platform
Configuration register setting