A Cisco Catalyst Switch includes hundreds of commands to fulfill the requirement of network. In this article, I will explain the essential commands. As a instructor I can personally assure you that those individuals who spent time in learning the essential technologies have always had a much higher chance of success, both in exam and on job.
To take full advantage of this article I recommend you to use Packet Tracer software. Packet Tracer is a network simulator software developed by Cisco System for critical hands-on experience. This software includes all necessary devices for the practice of entry level cisco exams. You can download Packet Tracer freely from our site. For this article I assume that you have packet tracer installed on your system.
Command reference, mode, and, purpose
User EXEC: Allow you to connect with remote devices, perform basic tests, temporary change terminal setting, list system information
Privileged EXEC: Allow you to set operating parameters. It also includes high level testing and list commands like show, copy, debug.
Global Configuration: Contain commands those affect the entire system
Interface Configuration: Contain commands those modify the operation of an interface
VLAN configuration: Create new VLAN or configure, modify, delete existing VLAN.
Line configuration: Line configuration commands modify the operation of a terminal line. Line configuration commands always follow a line command, which defines a line number.
Example of Cisco Switch Basic Configuration
switch>enable
switch#configure terminal
switch(config)#hostname switch1
switch1(config)#line console 0
swicth1(config-line)#password linecon4321
switch1(config-line)#login
switch1(config-line)#exit
switch1(config)#line aux 0
switch1(config)#line vty 0 15
siwtch1(config-line)#telnet4321
switch1(config-line)#login
switch1(config--line)#exit
switch1(config)#exit
switch1#copy run start
How to reset switch to factory defaults
Switch>enable
Switch#delete flash:vlan.dat
Delete filename [vlan.dat]? [Press Enter Key]
Delete flash:vlan.dat? [confirm] [ Reconfirm by pressing enter key]
Switch#erase startup-config
Switch#reload
How to set IP address in Switch
IP address is the address of device in network. Switch allows us to set IP address on interface level. IP address assigned on interface is used to manage that particular interface. To manage entire switch we have to assign IP address to VLAN1( Default VLAN of switch). We also have to set default gateway IP address from global configuration mode. In following example we would assign IP 172.16.10.2 255.255.255.0 to VLAN1 and set default gateway to 172.16.10.1.
Switch>enable
Switch#configure terminal
Switch(config)#interface vlan1
Switch(config-if)#ip address 172.16.10.2 255.255.255.0
Switch(config-if)#exit
Switch(config)#ip default-gateway 172.16.10.1
How to set interface description
Switches have several interfaces. Adding description to interface is a good habit. It may help you in finding correct interface. To add description use following commands. In following example we would add description Development VLAN to interface FastEthernet 0/1.
Switch(config)#interface fastethernet 0/1
Switch(config-if)#description Development VLAN
How to clear mac address table
Switch stores MAC addresses in MAC address table. Gradually it could be full. Once it full, switch automatically starts removing old entries. You can also clear these tables manually from privileged exec mode. To delete all entries use following command
switch#clear mac address-table
To delete only dynamic entries use
switch#clear mac address-table dynamic
How to add static MAC address in CAM table
For security purpose sometime we have to add mac address in CAM table manually. To add static MAC address in CAM table use following command
Switch(config)#mac address-table static aaaa.aaaa.aaaa vlan 1 interface fastethernet 0/1
How to set duplex mode
Switch automatically adjust duplex mode depending upon remote device. We could change this mode with any of other supported mode. For example to force switch to use full duplex mode use
Switch(config)# #interface fastethernet 0/1
Switch(config-if)#duplex full
To use half duplex use
Switch(config)# #interface fastethernet 0/1
Switch(config-if)#duplex half
How to show the version of IOS
show version command provides general information about device including its model number, type of interfaces, its software version, configuration settings, location of IOS and configuration files, and available memories.
Switch>show version
How to show mac address table
Switch stores MAC address of devices those are attached with its interfaces in CAM table. We can use show mac-address-table command to list all learned devices. Switch uses this table to make forward decision. See our previous article to learn more about switch functions.
Switch>enable
Switch#show mac-address-table
How to show the running configuration
Configuration parameter values are created, stored, updated and deleted from running configuration. Running configuration is stored in RAM. We can use show running-config command to view the running configuration.
Switch>enable
Switch#show running-config
How to show startup config
Any configuration stored in RAM is erased when devices is turned off. We can save running configuration in NVRAM. If we have saved running configuration in NVRAM, it would be automatically loaded back in RAM from NVRAM during the next boot. As switch load this configuration back in RAM in startup of device, at NVRAM it is known as startup-config.
Switch>enable
Switch#show startup-config
How to show VLAN config
Switch#show vlan
How to show interface config
show interface command displays information about interfaces. Without argument it would list all interfaces. To get information about specific interface we need to pass its interface number as an argument. For example to view details about FastEthernet 0/1, use show interface fastethernet 0/1.
Switch#show interface
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