Introduction to IOS and Cisco Routers

1
Introduction to IOS and Cisco Routers
2
Memory Architecture
3
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

4
Memory Types
RAM (Working Memory)
NVRAM (Startup Config)
ROM (Basic IOS)
Flash (IOS)
5
Configuration and IOS Images
6
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)

7
Saving a Configuration
Copy startup-config running-config
RAM (Running-Config)
Merged
Replaces
NVRAM (Startup-Config)
Copy running-config startup-config
8
Syntax of the Copy Command
Copy From-Location To-Location Where From-
and To-Location - tftprunning-configstartup-con
fig tftp a trivial ftp server located
somewhere on the network
9
Entering the Configuration

• Setup Mode
• If no configuration exists when the router boots,
  it enters setup mode
• Router hasnt 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

10
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

11
Viewing Configurations
Show running-configstartup-config
12
The CLI and Getting Help
13
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 gt sh int

14
Command Line Interface

• If a command has an error the command will be
  repeated and a will mark the location of the
  erroraccess-list 110 permit host 1.1.1.1
  Invalid input detected
  at marker.

15
Command History

• Up and Down arrows scroll through command history
• Also ctrlp (up) and ctrln (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

16
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

17
Connecting to the Router
18
Connecting to the Router

• Console
• Connect directly to console port and use a
  terminal program like Windows Hyperterminal or
  Linuxs 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

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IOS Modes
20
IOS Modes
Telnet Aux Console
User Mode Routergt
enable
disable
Privileged (Enable) Mode Router
21
IOS Configuration Modes
Privileged Mode Router
Config terminal (config t)
Router ltprotocolgt (Router rip)
Configuration Mode Router(config)
Router Configuration Mode Router(config-router)
Interface ltinterfacegt (interface ethernet 0)
Interface Configuration Mode Router(config-if)
22
Router Interfaces
23
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.

24
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

25
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

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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

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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

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Assigning an IP Address

• IP addresses are assigned in interface
  configuration mode

Routerconfig 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
29
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
30
Setting the Serial Encapsulation

• Well 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)enca
psulation frame-relay
31
Passwords
32
Privileged Mode Passwords

• Enable password
• Enable password ltpasswordgt
• Enable password is shown in clear text
• Not used if enable secret password is set
• Enable secret password
• Enable secret ltpasswordgt
• Enable secret password is encrypted

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User Mode Passwords
Enter configuration mode

• Console Line console 0 Login Password
  ltpasswordgt
• Auxiliary Line aux 0 Login Password
  ltpasswordgt
• Telnet Line vty 0 4 Login Password ltpasswordgt

Require login
Set password
Most routers have 5 telnet lines. This command
sets all five.
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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 ltpasswordgt no
  service password-encryption

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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

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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 ltrunning-config/startup-config,tftpgt
  ltrunning-config/startup-config,tftpgt

37
IOS Commands to Know

• Show interface
• Show controllers
• Clock rate
• Ip address
• Show Version
• Show flash