1. INTRODUCTION TO IOS
AND CISCO ROUTERS
By
Anil Kumar Vishwakarma
MCA,MCTS,CCNA

2. CISCO ROUTER IOS
oThe Cisco IOS (Internetwork Operating System) was
created to deliver network services and enable networked
applications. It runs on most Cisco routers.
oSome of the important things that the Cisco router IOS
software is responsible for include
o Carrying network protocols and functions.
o Connecting high-speed traffic between devices.
o Adding security to control access and stop unauthorized
network use.
o Supplying network reliability for connecting to network
resources.

3. 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

5. INTERNAL COMPONENT

6. 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.

7. COMPUTER CONSOLE CONNECTION

8. MODEM CONNECTION

9. 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.

10. MEMORY ARCHITECTURE

11. 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

12. MEMORY TYPES
RAM
(Working Memory)
Flash
(IOS)
ROM
(Basic IOS)
NVRAM
(Startup Config)

13. CONFIGURATION AND IOS
IMAGES

14. 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)

15. SAVING A CONFIGURATION
RAM
(Running-Config)
NVRAM
(Startup-Config)
Copy running-config startup-config
Copy startup-config running-config
Merged
Replaces

16. 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

17. 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

18. SETUP MODE
 Setup Mode allows configuration of:
 Interface summary
 Router hostname
 Passwords
 SNMP
 Various network protocols
 DECnet, Appletalk, IP, IPX
 Routing protocols
 Interfaces
 When finished setup mode gives the user
the option of copying the configuration to
NVRAM and RAM

19. VIEWING CONFIGURATIONS
Show {running-config|startup-config}

20. THE CLI AND GETTING HELP

21. 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

22. 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.

23. 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

24. 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

25. CONNECTING TO THE ROUTER

26. 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

27. IOS MODES

28. IOS MODES
User Mode
Router>
Privileged (Enable) Mode
Router#
disable enable
Telnet Aux Console

29. IOS CONFIGURATION MODES
Configuration Mode
Router(config)#
Privileged Mode
Router#
Config terminal
(config t)
Interface Configuration Mode
Router(config-if)#
Interface <interface>
(interface ethernet 0)
Router Configuration Mode
Router(config-router)#
Router <protocol>
(Router rip)

30. ROUTER INTERFACES

31. 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.

32. 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

33. 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

34. 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

35. 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

36. 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

37. SETTING THE CLOCK RATE
 On serial connections the DCE must set a
clock rate to synchronize communication
 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
Router(config)#int s0
Router(config-if)#clockrate 2000000

38. 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

39. PASSWORDS

40. PRIVILEGED MODE PASSWORDS
 Enable password
 Enable password <password>
 Enable password is shown in clear text
 Not used if enable secret password is set
 Enable secret password
 Enable secret <password>
 Enable secret password is encrypted

41. USER MODE PASSWORDS
 Console
Line console 0
Login
Password <password>
 Auxiliary
Line aux 0
Login
Password <password>
 Telnet
Line vty 0 4
Login
Password <password>
Enter configuration mode
Require login
Set password
Most routers have 5 telnet
lines. This command sets
all five.

42. 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 <password>
no service password-encryption

43. 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

44. 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 <running-config/startup-config,tftp>
<running-config/startup-config,tftp>

45. IOS COMMANDS TO KNOW
 Show interface
 Show controllers
 Clock rate
 Ip address
 Show Version
 Show flash

46. Thank You