INTRODUCTION TO IOS AND CISCO ROUTERS By Anil Kumar Vishwakarma MCA,MCTS,CCNA
CISCO ROUTER IOS o The Cisco IOS (Internetwork Operating System) was created to deliver network services and enable networked applications. It runs on most Cisco routers.
o Some of the important things that the Cisco router IOS software is responsible for include o o o o
Carrying network protocols and functions. Connecting high-speed traffic between devices. Adding security to control access and stop unauthorized network use. Supplying network reliability for connecting to network resources.
CISCO ROUTER
Router uses to connect: Subnet with another Subnet (By LAN Interface). LAN with another LAN (By WAN Interface). LAN with WAN (By WAN Interface). WAN with another WAN (By WAN Interface). Router Consist of External Components (Interfaces) and Internal Components
INTERNAL COMPONENT
CONNECTING TO A CISCO ROUTER You can connect to a Cisco router to configure it, verify its configuration, and check statistics. There are Three ways to do that:
Console Session. Auxiliary Session. Telnet Session can’t use this method after router has taken valid IP address.
COMPUTER CONSOLE CONNECTION
MODEM CONNECTION
BRINGING UP A ROUTER
When you first bring up a router, it will takes this Boot Sequence:
Perform POST (Power On Self Test) which is small program stored in ROM to check router components. Load IOS image from Flash memory and decompress it into RAM. Display the information from POST. Running Valid Configuration (Startup Conf). If no configuration router will go into Setup mode.
MEMORY ARCHITECTURE
MEMORY TYPES RAM
Used to store working tables as well as running IOS image
ROM
Stores a bootable IOS image that provides basic functionality as well as a barebones interface called the ROM Monitor (ROMMON)
Flash
Memory
Stores the full function IOS image and is the default location for IOS at boot
NVRAM
Stores startup configuration file
MEMORY TYPES
RAM (Working Memory)
Flash (IOS)
NVRAM (Startup Config)
ROM (Basic IOS)
CONFIGURATION AND IOS IMAGES
CONFIGURATION FILE The
configuration is a text file that contains configuration commands that are executed at startup When the router boots a copy of the config in NVRAM (startup-config) is executed to establish the initial configuration Configuration commands entered while the router is running are entered into the temporary configuration stored in RAM (running-config)
SAVING A CONFIGURATION
Copy startup-config running-config RAM (Running-Config) Merged
Replaces NVRAM (Startup-Config)
Copy running-config startup-config
SYNTAX OF THE COPY COMMAND
Copy From-Location To-Location Where: From- and To-Location - {tftp|running-config|startup-config} tftp – a trivial ftp server located somewhere on the network
ENTERING THE CONFIGURATION Setup
Mode
If no configuration exists when the router boots, it enters setup mode Router hasn‟t been configured before Someone used the „Erase Startup-Config‟ then rebooted NVRAM was damaged
Setup mode is a question and answer process that can be used to create basic configurations
Command
Line Interface (CLI)
Configuration commands entered at command prompt then saved to NVRAM
SETUP MODE Setup
Interface summary Router hostname Passwords SNMP Various network protocols
Mode allows configuration of:
DECnet, Appletalk, IP, IPX
Routing protocols Interfaces
When
finished setup mode gives the user the option of copying the configuration to NVRAM and RAM
VIEWING CONFIGURATIONS
Show {running-config|startup-config}
THE CLI AND GETTING HELP
COMMAND LINE INTERFACE Most
Cisco devices use a command line interface Commands can be entered and edited before they are executed by hitting the enter key Commands can be abbreviated as long as they are not ambiguous
e.g. Show Interface => sh int
COMMAND LINE INTERFACE
If a command has an error the command will be repeated and a “^” will mark the location of the error access-list 110 permit host 1.1.1.1 ^ %Invalid input detected at „^‟ marker.
COMMAND HISTORY
Up and Down arrows scroll through command history Also ctrl+p (up) and ctrl+n (down) Command history commands
Show history – shows commands in history Show terminal – shows terminal configurations and terminal history size (default = 10) Terminal history size – changes history buffer size up to a max of 256
GETTING HELP
Typing ? at any point will cause IOS to show what options exist at that point Just ? on a line will list all commands available in that mode Typing one letter followed by ? will show all commands that begin with the letter Adding ? after a command will show what arguments are available for the command
CONNECTING TO THE ROUTER
CONNECTING TO THE ROUTER Console
Connect directly to console port and use a terminal program like Windows Hyperterminal or Linux‟s Minicom
AUX
The auxiliary port is port you can attach a modem to Can also be used as a backup connection dial on demand circuit
TTY
Can use Telnet to connect to TTY once router has been configured initially Most routers have 5 TTY connections
IOS MODES
IOS MODES Telnet
Aux
Console
User Mode
Router> enable
disable
Privileged (Enable) Mode
Router#
IOS CONFIGURATION MODES Privileged Mode
Router# Config terminal (config t)
Router (Router rip)
Configuration Mode
Router Configuration Mode
Router(config)#
Router(config-router)#
Interface (interface ethernet 0) Interface Configuration Mode
Router(config-if)#
ROUTER INTERFACES
INTERFACES LANs
Ethernet (Ethernet 0, E0, E1, etc.) FastEthernet (FastEthernet 0, F0, F1, etc.) Token Ring (TokenRing 0, TO0, TO1, etc.)
WANs
Serial 0, S0, S1, etc.
INTERFACES ON EXPANSION CARDS
Interfaces on add in expansion cards include the slot number followed by a slash then the interface number
The first FastEthernet interface on a card in the first slot would be FastEthernet 0/0
On 7500 series routers three values are required (slot/port-adapter/port) so it would be FastEthernet 0/0/0 for example
LOOPBACK INTERFACES
Loopback interfaces are internal interfaces and treated like other interfaces
Loopback interfaces are never shutdown
Loopback interfaces are useful when you need an interface that will never go down
INTERFACE CONFIGURATION MODE
Use the Interface command in configuration or interface configuration mode to enter configuration mode Router(config)#interface e0 Router(config-if)#interface Lo0 Router(config)#interface s0/1
BRINGING UP AN INTERFACE
By default, all interfaces (except loopback interfaces) are in administrative shutdown mode To activate the interface use the no shutdown command in the interface configuration mode
ASSIGNING AN IP ADDRESS
IP addresses are assigned in interface configuration mode
Router#config t Router(config)#interface s0 Router(config-if)#ip address 129.130.32.1 255.255.224.0 Router(config-if)#no shutdown Router(config-if)#exit
SETTING THE CLOCK RATE On
serial connections the DCE must set a clock rate to synchronize communication Router(config)#int s0 Router(config-if)#clockrate 2000000
In the lab the 2501 that is a router is a DCE because the cable attached is a DCE cable so the clock rate must be set on this router The 2501 that is a Frame Relay switch is also a DCE but you do not configure this one
SETTING THE SERIAL ENCAPSULATION
We‟ll discuss this in more detail later in the semester but the data link layer protocol must be set for the Frame Relay link using the encapsulation command
Router(config)#interface s0 Router(config-if)#encapsulation frame-relay
PASSWORDS
PRIVILEGED MODE PASSWORDS
Enable password Enable password Enable password is shown in clear text Not used if enable secret password is set
Enable secret password Enable secret Enable secret password is encrypted
USER MODE PASSWORDS
Console Line console 0 Login Password
Auxiliary Line aux 0 Login Password
Enter configuration mode Require login
Set password
Telnet Line vty 0 4 Login Password
Most routers have 5 telnet lines. This command sets all five.
ENCRYPTING PASSWORDS User
mode passwords are normally stored in the configuration file in clear text
To
encrypt them use the following sequence of commands service password-encryption line console 0 login password no service password-encryption
IOS COMMANDS TO KNOW Enable/disable
Enable secret/password
Config Editing
commands Show history Show terminal Terminal history size Line
How to require login and set password for console, vty and aux
IOS COMMANDS TO KNOW Service
password-encryption
Banner Interface
Shutdown Know the interfaces commands for ethernet, fast ethernet, serial, token ring and loopback Description
Hostname Show
running/startup-config Copy
IOS COMMANDS TO KNOW Show interface Show controllers Clock rate Ip address Show Version Show flash
Thank You
