Chapter 6 – Using the CLI

Switches can be operated: 

  • Using CLI. 
  • Provide web interface (user can connect to the web server running in switch). 
  • Switches can be controlled and operated using network management software. 
  • Some switches from the 2960 family have 48 UTP  ports (10/100/100) which means they can negotiate the use of cabling 
  • Switch’s physical connectors are interfaces or ports. 
  • The interface has type and number. 
  • interface type can be Ethernet, FastEthernet, Gigabit Ethernet, and so on. 
  • Naming interfaces: some switches use x/y or x/y/z port numbering methods.   
  • Cisco has an OS, IOS Internetwork Operating System 
  • CLI can be accessed by the console, telnet, and SSH 
  • Telnet and ssh use the IP network  
  • The console is a physical port built for accessing the CLI by laptop or PC 

Accessing switch using console connection

  • Contains three things: console cable, serial port on PC, and console port on switch 
  • The serial port has 9 pins (called DB-9) and its rectangular D-shell connector 
  • Rollover cable has pinouts and they are ordered as follows: 1 to 8, 2 to 7, 3 to 6, 4 to 5, 5 to 4, 6 to 3, 7 to 2, 8 to 1 
  • After the cable is plugged in, we need a software that will be used as a way to access CLI 
  • Terminal emulator software must be installed 
  • It treats all data as text, accepts the text typed by the user and sends it over the console cable to the switch 

Accessing the CLI with Telnet and SSH

  • Traffic flows through the IP network and not through a console cable. 
  • Telnet uses telnet client and telnet server concept 
  • Telnet client is the user that enters commands and sends them to switch 
  • Telnet server accepts commands and replies back to the user 
  • Telnet uses port 23  
  • Sends all data as plain text (not encrypted) 
  • SSH uses TCP, port 22 

User and Enable Modes

  • User EXEC – exec means switch executes a command  
  • User mode 
  • Enable or privileged mode 
  • Cisco IOS stores configuration commands in a configuration file 

Three ways to remove startup configuration files

  • write erase 
  • erase startup-config 
  • erase nvram 

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