Essentials of Cisco routers configuration

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Essentials of Cisco routers configuration

• Nevenko Bartolincic
• Nevenko.Bartolincic_at_CARNet.hr

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Introduction - Why?

• Cisco routers dominate the market
• we use them in our lab
• 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

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Command line editing

• all commands and strings can be abbreviated to
  their shortest unique prefix (ex. sh run)
• arrow keys will move the cursor to the left and
  right on the command line
• command history is accessed via up and down
  arrows
• previous commands can be edited and re-entered

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Command Line Editing

• Advanced features
• A Move to left of line
• B Move to right of line
• D Delete character under cursor
• K Delete to end of line
• F Move forward
• B Move backward
• P Move to previous line
• N Move to next line

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Network interfaces

• each network interface is identified by type and
  number
• types can be abbreviated, numbers start at 0
• ethernet0 e0
• serial2 s2
• tokenring1 to1
• virtual interfaces for various purposes
• loopback
• tunnel
• vlan

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Example

• routergt enable
• router conf t
• router(config) int e0
• router(config-if) ip addr 10.0.0.10
  255.255.255.0
• router(config-if) no shut
• router(config-if) z
• router sho ip int e0

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Useful commands

• set the console password
• router(config) line con 0
• router(config-line) password mysecret
• set the vty passwords
• router(config-line) line vty 0 4
• router(config-line) password mysecret
• router(config-line) exit
• set the enable password
• router(config) enable password mysecret
• router(config) service password-encryption
• router(config) Z

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Useful commands (cont.)

• list all interfaces in a router
• router show interface
• display running configuration
• router show running-configuration
• save the configuration
• router copy running-config startup-config
• display IOS information
• router show version
• display contents of flash
• router show flash
• display running network protocols
• router show protocols

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Useful commands (cont.)

• non-console session can receive messages
• terminal monitor
• disable console logging
• no logging console (config)
• configure router to use syslog
• logging on (config)
• logging ltip-addressgt
• store in buffer
• logging buffered (config)
• display current configuration of message logging
• show logging

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Useful commands

• configuring an interface
• ip address ltaddressgt ltmaskgt (config)
• static routing (config)
• ip route ltnetworkgt ltmaskgt ltaddressgt distance
• default route (config)
• ip route 0.0.0.0 0.0.0.0 ltaddressgt
• ip default-network ltnetworkgt
• in the second case router determines next hop
• netmask format (decimal,hexadecimal,bit-count)
• terminal ip netmask-format ltformatgt
• ip netmask-format ltformatgt (config)
• session break sequence
• CTRL-SHIFT-6 x

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If you want to know more

• Cisco courses (ICRC,ACRC)
• Cisco documentation (www.cisco.com)
• Cisco mailing list
• cisco-reguest_at_spot.colorado.edu
• search engine
• http//www.nexial.com/cgi-bin/ciscobody
• Books
• Managing IP Networks with Cisco Routers,
  Scott Bellew, OReilly and Associates
• TCP/IP Illustrated, Volume 1 The protocols,
  W. Richard Stevens, Addison-Wesley