Cisco IOS Software

1. Cisco IOS Software • Cisco’s operating system is called Cisco Internetwork Operating System (IOS) • IOS provides the following network services: • basic routing and switching functions • reliable and secure access to networked resources • network scalability

2. Access to Router • Cisco IOS software uses a command-line interface (CLI) as the console environment. • This environment is accessible via: • console session • Uses a low speed serial connection directly from PC to router • AUX port • Dialup with a modem through AUX port. Don’t need the router to be connected to network services • Telnet • Must have at least one interface configured with IP address, and virtual terminal sessions must be configured for login & password.

3. Cisco IOS Software • The Cisco CLI uses a hierarchical structure, called modes. • The IOS provides a command interpreter service known as the command executive (EXEC). • There are two access levels: • user EXEC mode • Has limited number of basic monitoring commands. The mode is identified by > • privileged EXEC • Requires password & also can require user ID. By this mode one can accesses all router commands. This modes is identified by #

4. Cisco IOS Software • Cisco IOS releases naming convention contain 3 parts: • platform on which the image runs • special features supported in the image • where the image runs & whether it has been zipped or compressed • It is of the form: xxxx-yyyy-ww • xxxx = Platform • yyyy = Features • ww = Format – where it executes

5. Cisco IOS Software Before installing a new Cisco IOS software image on the router, check to see if the router meets the memory requirements. Use the command: show version To find out amount of flash memory, use the command: show flash

6. Cisco IOS Software Cisco IOS has 3 distinct operating environments or modes: • ROM monitor • Performs the bootstrap process & provides low-level functionality & diagnostics. Used for password recovery. Can NOT be accessed thru any interface. • Boot ROM • Only a limited subset of Cisco IOS features are available. One is allowed to write to flash memory & is used primary to replace the Cisco IOS image stored in flash • Cisco IOS • Need the full IOS image as stored in flash

7. Initial Startup The major steps in initialization of a router are: • Power up self test (POST) • bootstrap loader in ROM executes • locate and load the operating system • locate and load the configuration files

8. Initial Startup • bootstrap loader • Simple set of instructions that tests hardware & initializes the IOS • locate & load IOS (determined by the configuration register stored in NVRAM) • flash • TFTP server • ROM • locate & load configuration files • NVRAM • TFTP server • console If no TFTP server is found, then the setup dialog is initiated.

9. Initial Startup After the system initializes correctly, the LED to the right of the AUX port will become green. (2500 series; 2600 light is in the front)

10. HyperTerminal The default parameters for the console port are: • console port: 9600 baud • data bits: 8 • no parity • 1 stop bit • no flow control

11. Router Modes • User Router> • Privilege Router# • Global configuration mode Router# config t • Only accessible from the privilege mode. • From this mode one can access: • interfaces • subinterfaces • line • router • router-map

12. HELP commands for the Router ? Ctrl-A – moves to the beginning of the command line Esc-B – move back one word Ctrl-B – move back one character (left arrow) Ctrl-E – move to the end of the command line Ctrl-F – move forward one character (right arrow) Esc-F – move forward one word Ctrl-P – recalls last or previous command (up arrow) Ctrl-N – recalls most recent command (down arrow) <Tab> - complete the entry

13. Router Commands • 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 (how IOS is booted)