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8/6/2019 Cisco Router Basics
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BasicBasic
Cisco routerCisco routerconfigurationconfiguration
Donald W. SmithDonald W. SmithNovember 2001November 2001
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Cisco Router Basics 2
Cisco IOS
n Cisco routers run IOS
IOS = Internetwork Operating System
n Current version of IOS is 12.x
n Command line interface
complete on-line help
full line editing, history
n
IOS supports everything anyone would everwant to do with router
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Cisco Router Basics 3
CLI Sessions
n CLI sessions can be initiated from:
Console port
Aux port (modem)
Telnet (virtual line = vty)l Multiple sessions are allows (0-4 for IOS 12.0)
l Cannot telnet into router if no password set
n Each port can be password protected (with
separate passwords)n It is possible to use user based authentication
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Cisco Router Basics 5
Router modes (cont.)
User mode router> Show router status and operation
Configuration cannot be viewed or altered
Privileged mode router#
Complete control over the router (anything can be setor reset)
Configuration cannot be altered
Configuration mode router(config)#
Used only for change of configuration Privileged mode commands are not available
Not password protected
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Cisco Router Basics 6
Router Mode commands
User
Privileged
Config
enable
config t
Ctrl Z
disable
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Cisco Router Basics 7
ROM
- Bootstrap- IOS- Rxboot
RAM
- Running IOS
- Running config
- Tables- Buffers
NVRAM
- startup-config
Flash
- IOS
- Other files
Router memory
1
2
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Cisco Router Basics 8
Router configurations
Two configurations: the active configuration (show running-config)
the startup configuration (show startup-config)
RAM
Active
config
Terminal
NVRAMStartup-config
NetworkTFTP config
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Cisco Router Basics 9
IOS Help System
n IOS has built-in help
n At the beginning of command line ?? will give a list ofall commands available in the current mode
If more than one screen,
l Space bar shows next screen
l Enter shows one more line
n Command (space) ?? showsshows a list of options
No Enter key is required
Retypes line ready for additional input
n If used after a character, help displays all
commands with the same prefix
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Cisco Router Basics 10
Command Line Editing
n All commands and strings can be abbreviated totheir shortest unique prefix (ex. sh run)
n Arrow keys will move the cursor to the left and
right on the command line
n Command history is accessed via up and downarrows
n Previous commands can be edited and re-
entered
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Cisco Router Basics 11
Command Line Editing
Advanced features:
^A To left end of line
^E To right end of line
^D Delete character under cursor ^K Delete to end of line
^F One character forward (or right ->)
^B One character backward (or left
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Cisco Router Basics 12
Network interfaces
n Each network interface has a type and number
n Types can be abbreviated, numbers start at 0
ethernet0 e0
Fastethernet0 f0 serial2 s2
tokenring1 to1
n Virtual interfaces are for various purposes
loopback tunnel
vlan
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Cisco Router Basics 13
Example Sequence
router> enable
router# conf t
router(config)# int e0
router(config-if)# ip addr192.168.1.10 255.255.255.0
router(config-if)# no shut
router(config-if)# ^z
router# sho ip int e0
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Cisco Router Basics 14
Passwords
n There are five (5) passwords Enable
l Password Legacy support only
l Secret Newer, encrypted password Console port
Aux port
Vty (telnet) port
n You can also use a tacacs server tomanage all passwords in your network
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Cisco Router Basics 15
Setting Passwords
n set the enable secret password router(config)# enable secret
router(config)# service password-encryption
router(config)# ^Z
n Set the console password router(config)# line con 0
router(config-line)# password
router(config-line)# login
n Set the telnet password (for all sessions) router(config-line)# line vty 0 4
router(config-line)# password
router(config-line)# login
router(config-line)# exit
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Cisco Router Basics 16
Useful Commands
n List all interfaces in a router router# show interface
n Display running configuration router# show running-configuration
n
Save the configuration (ram to NV-RAM) router# copy running-config startup-config
Router# copy run start
n Show IOS version, interfaces and memory router# show version
n Show contents of flash (IOS image) router# show flash
n Show running network protocols router# show protocols
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Cisco Router Basics 17
n Non-console session can receive messages
terminal monitor
n Disable console logging
no logging console (config)
n Configure router to use syslog
logging on (config)
logging
n Store in buffer
logging buffered (config)
n Display current configuration of message logging
show logging
Logging commands
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