Basic Cisco Switch Configuration

Outline

1. How to access the switch
   1. Command Modes
   2. Verify current settings on switch if any and remove them if found.
   3. Switch Setup
      1. Setting up your hostname
      2. Setting up Telnet
      3. Configuring your enable password
      4. Encrypting your passwords
      5. Setting up your switch IP Address
      6. Setting up Default Gateway
      7. Saving your configuration
2. Basic port configuration
   1. Setting up access ports
   2. Setting up a Trunk port
   3. Using the Range command

Accessing the Switch:

We need to connect to the switch using either a Cisco USB cable or a console cable with a usb-serial adapter.  Most computers today do not come with a serial port anymore so I recommend purchasing a usb-serial adapter.  You can find these pretty cheap on Amazon or Ebay

After you have installed the drivers for your usb-serial adapter, we need to setup putty to communicate with the switch.  I’m going to be using the below setting for my switch.

Command Modes:

Mode	Symbol	Accessing mode	Exiting mode
User Exec Mode	Switch>	Default Mode, basic show command available	Exit
Privileged EXEC Mode	Switch#	The “Enable” command will move you into this mode	Exit
Global Configuration Mode	Switch(config)#	“Configure Terminal” or “Config t” command from Privileged mode	Exit or Ctrl + Z to move back to EXEC mode
Interface Configuration	Switch(config-fi)#	Use Interface (interface name+number> command from global configuration mode	Exit will move you back to global mode, END will move you back to Privileged mode Switch#

Verify current settings on the Switch:

So, I like to verify the switch is in a fresh configuration, meaning that the switch is in it’s default factory state.  If you are unsure I would delete the configurations and reload the switch.

Steps to reload a switch……

Configuring the Switch Hostname:

Alright, let’s move from EXEC mode -> Privileged Mode, (EN or Enable) -> Configure Terminal (Config T).  Now type the following command -> Hostname “NAME”.

Switch# hostname 3560-24

Switch>enable
Switch#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)#hostname 3560-24
3560-24(config)#
3560-24(config)#
3560-24(config)#

We should now see the CLI change from SWITCH# to 3560-24#

Setting up Telnet:

Alright let’s move into the Global Configuration mode, then into Interface Configuration. 

3560-24>en
3560-24#config t
Enter configuration commands, one per line.  End with CNTL/Z.
3560-24(config)#line con 0

We will now be setting line CON 0 with a password and login rights

3560-24>en
3560-24#config t
Enter configuration commands, one per line.  End with CNTL/Z.
3560-24(config)#line con 0
3560-24(config-line)#password cisco
3560-24(config-line)#login

Now lets jump right from CON 0 into VTY 0 4 (Telnet Lines 0 thru 4) and setup the password and login commands.

3560-24(config-line)#line vty 0 4
3560-24(config-line)#password cisco
3560-24(config-line)#login
3560-24(config-line)#
3560-24(config-line)#exit
3560-24(config)#exit
3560-24#

After we have set both of these up, I like to exit the switch and test to make sure that we can at least get back into the switch before we save to configuration.

Alright, everything is looking good so let’s configure the Enable password.  We will move back into Privileged EXEC mode then into Global configuration mode.  Using the command “enable secret <password>” will make our password encrypted.  This command does not encrypt our VTY and Con 0 passwords, so we will also run the command “Service Password-Encryption”

3560-24>en
3560-24#config t
3560-24(config)#enable secret cisco
3560-24(config)#service password-encryption
3560-24#exit

Now before you save your configuration.  I like to logout and login to verify all passwords are working correctly.  Now if you use the command “show running-config” we should see that our enable passwords and line passwords are encrypted.

Setting the Switches IP Address:

We are going to be starting from the EXEC mode and move to the Interface Configuration mode.

3560-24>enable
Password:
3560-24#config t
Enter configuration commands, one per line.  End with CNTL/Z.
3560-24(config)#int Vlan 1
3560-24(config-if)#

Now lets configure Vlan 1 with an IP Address and enable the interface.

3560-24(config)#int vlan 1
3560-24(config-if)#ip address 10.10.10.1 255.255.255.0
3560-24(config-if)#no shutdown
3560-24(config-if)#
17:04:18: %LINK-3-UPDOWN: Interface Vlan1, changed state to up

Now that we have an IP Address on the switch, I also like to setup a default-gateway just in case we have other subnets on our network we need to talk too.  If all your devices are on Vlan 1 then you don’t have to do this, but I would highly suggest you do.

3560-24(config)#ip default-gateway 10.10.10.254

Verifying the gateway

3560-24#sh ip route
Default gateway is 10.10.10.254

Host               Gateway           Last Use    Total Uses  Interface
ICMP redirect cache is empty
3560-24#

Saving your Configuration:

Saving your Configuration by either entering “wr” or “copy running-config startup-config”

3560-24#wr
Building configuration...
[OK]

or

(This is the Cisco preferred method)

3560-24#copy running-config startup-config
Destination filename [startup-config]?
Building configuration...
[OK]
3560-24#

Alright, let’s move on to configuring our interfaces with some basic settings.

Basic Access Port:

The two commands we are going to use are “Switchport mode access” and “Switchport access vlan <number>”.  The “switchport mode access” command disables DTP – Dynamic Trunking Protocol on the specified interface, which basically turns off trunk negotiation.

3560-24#config t
Enter configuration commands, one per line.  End with CNTL/Z.
3560-24(config)#int fa0/1
3560-24(config-if)#switchport mode access
3560-24(config-if)#switchport access vlan 1
3560-24(config-if)#

Now lets verify our configuration, you will not see “switchport access vlan 1” as it already in Vlan 1, but if we had configured Vlan 10 we would see it on the port config.  By default all ports are in Vlan 1 unless otherwise configured.

Vlan 1:

Vlan 10:

 I also like to setup “Spanning-tree Portfast” so the port will come up as fast as possible.  You will see a warning message when you enter this command, as it’s important to know not to configure “Portfast” if you are connecting this port to other Hubs, Switches, etc.

3560-24#config t
Enter configuration commands, one per line.  End with CNTL/Z.
3560-24(config)#int fa0/1
3560-24(config-if)#spanning-tree portfast

Here is a screenshot of the warning and the now configured port.

Basic Trunk Port:

This is a basic Trunk port configuration if you have multiple Vans and are needing them to pass to another switch.  I’m not going to get into much about trunk ports as I’ll be doing another post and video on this topic, but the below commands will configure a trunk port and pass all configured vlans thru the port.

3560-24#config t
Enter configuration commands, one per line.  End with CNTL/Z.
3560-24(config)#int fa0/2
3560-24(config-if)#switchport trunk encapsulation dot1q
3560-24(config-if)#switchport mode trunk
3560-24(config-if)#end

Verifying configuration:

Extra Knowledge:

If you want to configure multiple ports at one time you can use the “Interface Range” command to select contiguous ports.

3560-24#config t
Enter configuration commands, one per line.  End with CNTL/Z.
3560-24(config)#int range fa0/3 - 10
3560-24(config-if-range)#switchport mode access
3560-24(config-if-range)#switchport access vlan 10
3560-24(config-if-range)#spanning-tree portfast

You can verify your config using “show running-config” and we will see all the ports configured. 

Thanks for reading and I hope this helped!