Essentials of Cisco routers configuration

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Essentials of Cisco routers configuration
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Introduction - Why?

• Cisco routers are most common used in the market
• we use them in our lab too
• learning the basics makes lab exercises easier

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Router basic

• Cisco routers run the Internetwork Operating
  System (IOS)
• IOS support everything anyone would ever want to
  do with router
• command like interface, much like shell
• complete on-line help
• full line editing, including history

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Router components
ROM
RAM
NVRAM
Flash
- Bootstrap - IOS - Rxboot
- Active config - Tables - Buffers
- Startup config
- IOS - Other files
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Router modes
New session
password
User
enable
password
Privileged
config term
Configuration
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Sessions

• Sessions can be initiated from direct line
  (console, aux) or virtual line (vty)
• each line can be password protected (with
  separate passwords)
• it is possible to use user based authentication

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Router modes (cont.)

• User mode
• user can examine router status and operation.
• configuration cannot be viewed or altered from
  user mode
• prompt routergt
• Privileged mode (root)
• complete control over the router (anything can be
  set or reset)
• configuration cannot be altered
• prompt router

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User modes (cont.)

• Configuration mode
• used only for change of configuration
• not password protected from privileged mode
• privileged mode commands dont have meaning in
  configuration mode
• most statements can be removed from the
  configuration with the prefix no (ex. no
  shutdown)
• prompt router(config)

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Router configurations

• Two configurations
• the active configuration (show running-config)
• the startup configuration (show startup-config)

Terminal
RAM Active config
NVRAM
Flash
Network
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On line help

• IOS have built-in help
• at any point user may type ? and receive a list
  of what the executive expect to see next
• when used after character, help displays all
  command with the same prefix
• at the beginning of command line ? will give a
  list of all commands available in the current mode