How To Configure Your Switch

In This Lesson We Will:

  • Learn How To Connect Devices
  • How to configure your Cisco Switch
  • Learn Various CLI commands

Configuring Your Switch

Once you’ve unboxed your switch, it’s basically ready to go and forward traffic immediately after connecting it to your network. Switches are handy that way, they’re plug-n-play. However, they do require some configuration if you wish to connect remotely using SSH or Telnet, configure VLANs, etc. We’ll touch on that today. However, because the set up is so similar to setting up a router, I recommend you read this lesson alongside the Router Configuration lesson (Setting Up Your Cisco Router – Every Day Tech CCNA 200-301 – (every-day-tech.com))

Once you’ve connected your switch, there are two modes, much like in your router, that you’ll have access to configure through, and you must connect physically to the switch as Telnet or SSH won’t be set up:

Standard/User EXEC Mode – This is the mode the user is placed when immediately upon opening the CLI for the switch. Very limited monitoring and troubleshooting commands, ‘show’ and ‘ping’

Privileged EXEC Mode – This provides full access to the device commands, including configuration and management. This is your “enable” mode.

Helpful Tips

If you’re ever not sure which command to use or how to complete the command, you can simply start typing the command, and press ‘?’, and the CLI will give you the option for outputs:

The IOS is also set up to notify you whenever a command is input incorrectly and will display an error message.

Switch History and Examination Commands

Switches also keep a history buffer of the last 10 commands that were input. To see the history buffer, use ‘show history’ to display the commands currently stored in the buffer, and ‘terminal history’ to enable a longer terminal history length. Terminal History can store up to 256 command lines.

Below is a list of ‘show’ commands, and what they verify when you are troubleshooting your switch:

Show – Output

  • interface – shows the available interfaces on the switch
  • flash – shows the operating systems
  • startup-config – shows the NVRAM, backup configuration
  • memory – shows configured memory
  • stacks – shows configured stacks
  • buffers – shows configured buffers
  • running-config – shows the active configuration file

Common Switch Configuration Commands

Below is a table of most, if not all of the configuration CLI commands you would use to set up your switch for the first time. These aren’t in order of use:

Configure VLAN1:

Configure and interface to a new VLAN:

Duplexing and Port Speeds

There are three things to keep in mind when setting up ports on a switch. It’s worth noting though, for the most part, the switch will auto-config these settings for optimal performance. There are times though when an administrator would need to manually configure the duplex and speed of ports and interfaces.

Half-Duplex – Unidirectional data flow. A device can only send or receive on an ethernet LAN, one at a time.

Full-Duplex – Bidirectional data flow. A device can both send and receive on an ethernet LAN simultaneously. This means that a full-duplex port can take the bandwidth of both the device and its own port, and effectively double it. Two 100mpbs interfaces can transmit and receive at 100mbps, providing 200mbps of bandwidth.

Port Speed – This simply the bandwidth the port is running at. The most common speeds are 100mbps, 1Gbps, and 10Gbps.

Line, Protocol, and Interface Status

The CLI command ‘show interfaces’ will give you vital information about the performance of all interfaces on the switch. Interfaces on a switch are typically either ‘up’ or ‘down’, with some variation between the two depending upon how the interface has been set up. Below is a list of interface codes, and what they mean:

Line Status – Protocol Status – Interface Status – What It Means

Administratively Down – Down – disabled – ‘shutdown’ cmd configured

Down – Down – notconnect – Typically a cabling issue

Up – Down – notconnect – A L2 problem on L3 switches

Down – Down (err-disabled) – err-disabled – Port security disabled interface

Up – up – connect – Interface working as expected

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Thank you for reading!

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