Introduction to the Cisco IOS

1
Chapter 4

• Introduction to the Cisco IOS

2
Cisco Internetwork Operating System (IOS)

• Most Cisco stuff runs on same OS
• Uses command line interface (CLI)
• Handles protocols and functions
• Controls security
• Scaleable
• Reliable

3
Connecting to a Cisco Router

• Configure router, verify configuration, check
  statistics
• Three ways to connect
• Console port, often used first to set up router
  (RJ-45 jack)
• Auxiliary port for modem access (RJ-45)
• Telnet to any active interface
• Serial interfaces for WANs, AUI for Ethernet

4
2501 Router
5
Bringing up a Router

• Power on self-test (POST)
• Then, loads Cisco IOS from flash memory
• Flash memory is electronically erasable
  programmable read only memory (EEPROM)
• IOS loads and looks for startup-config file in
  nonvolatile RAM (NVRAM)
• No startup-config? Then router enters setup mode
  for you to configure it

6
Setup Mode

• Basic Management Setup to get the thing started
  and allow connectivity
• Extended Setup to configure global parameters and
  each interface
• Defaults are provided in
• Or, use Command-Line Interface
• Dont enter the initial configuration dialog
• Router then checks all interfaces
• Router then sits at prompt and waits for you

7
Passwords Can Be Confusing

• enable secret is password to get into
  configurations
• enable password is older version, you can set it
  and not use it ever again if enable secret is set
• virtual terminal password is used when telnetting
  to router (must have one before telnet is
  allowed)

8
The Interfaces

• Can set
• duplex mode
• IP address
• Subnet mask
• Router then displays your settings
• Choosing not to configure during bootup brings
  you to CLI

9
Logging into the Router

• User mode
• Routergt
• Used mostly to view statistics
• Routergt logout exits
• Routergt enable enters privileged mode
• Privileged mode
• Router
• Used to view change router configuration
• Router disable goes back to user mode
• Router logout exits

10
Overview of Router Modes

• Global changes
• config terminal or config t
• Changes made to running-config (DRAM)
• To change the startup-config (NVRAM)
• config memory or config mem
• Note Any configuration changes need to be placed
  into RAM. Typing config mem or config net (from a
  TFTP host) will replace the current running-config

11
Configuration and CLI Prompts

• Global configuration prompt
• Router(config)
• Interfaces
• Router(config-if)
• Sub-interfaces
• Router(config-subif)
• Line Commands
• Router(config-line)
• Routing Protocol Configurations
• Router(config-router)

12
Editing Help Features
13
Editing Help Features

• Commands starting with a certain letter
• Routerc?
• clear clock configure connect copy
• Router clock ? shows next options for clock
• Enhanced editing commands on pp. 161-162
• Router-command history shows recent commands used
  (p. 162)
• show history (last 10 commands)
• Gathering Basic Routing Information
• show version

14
Hands-On Labs 4.1- 4.2

• Pages 192-194

15
Setting the Passwords

• 5 passwords
• 1st two used to set your enable password
• Used to secure privileged mode Routergtenable
• Other three are used to configure a password in
  user mode via
• console port
• auxiliary port
• Telnet

16
Passwords

• Enable passwords
• Router(config)enable password cisco
• Router(config)enable secret cisco
• Auxiliary password
• Console password
• Telnet Password (must be set before telnet
  allowed)
• Router sh run will display passwords! To
  encrypt
• Router(config)service password-encryption

17
Hands-On Labs 4.3- 4.4

• Pages 194-196

18
Banners

• Users admins see them when logging in
• Types
• exec
• incoming
• login
• Message of the day (motd) is most common,
  displays for all users arriving on any port
• Notice delimiting character

19
Router Interfaces

• Routers have interfaces to connect networks
  serial, ethernet, fast ethernet
• How to set interfaces?
• Router show int e0 lets you check check status
  of Ethernet interface
• Router config t enters configuration mode
• Router(config) int e0 to work with Ethernet
  interface
• Router(config-if) no shutdown brings it up
• Router(config-if) shutdown takes it down

20
Setting IP Address

• Configuring an IP address on an interface
• Router(config)int e0
• Router(config-if)ip address 172.16.10.2
  255.255.255.0
• Router(config-if)no shut

21
Serial Interfaces

• Serial interfaces usually are DTE and connect to
  CSU/DSU, which is the DCE
• CSU/DSU usually provides the clocking
• In a lab, one router will be DTE and the other
  will be DCE
• Router(config) int s0
• Router(config-if) clock rate 64000
• Clock rate is in bits per second
• Set bandwidth for routing protocols to use
• Router(config-if) bandwidth 64
• Bandwidth is in KB per second

22
Hostnames Descriptions

• Hostnames locally significant (not used as
  network name)
• Router(config) hostname todd
• todd(config)
• Descriptions can make printouts easier to read
  (see page 205)
• Atlanta(config) int e0
• Atlanta(config-if) description Sales Lan

23
Viewing, Saving Configurations

• Viewing Saving Configurations
• running-config saved in DRAM
• startup-config saved in NVRAM
• Router copy run start
• Router sh run
• Router sh start
• Router erase startup-config

24
Verifying Your Configuration

• Tools to check your config (pp. 207-212)
• show running-config
• show startup-config
• ping an IP address
• show cdp nei detail to find out IP addresses
• trace to discover path through network
• telnet to devices with IP addresses
• sh interface to see one interface
• sh int e0 sh int s1 (line up/down protocol
  up/down)
• sh controllers s 0 (notice the space)

25
Hands-On Lab 4.5

• Pages 197-198