Cisco is defiantly the name of the game when it comes to networking equipment. They are pretty much what you would call top DOG when it comes to business networks. Cisco builds switches, routers, firewalls, cache engines, IDS/IPS sensors, wireless AP, wireless bridges, and the list could literally go on and on. Well I am going to get you started on some basic commands you can use on a Cisco Switch.

Cisco is evolving to more and more web-based configuration, but you if are anything like me you want the CLI (command line interface) to make all your changes. Well the first thing you will obviously have to do is connect to the switch. Lets assume the we have a single switch that is connecting three computer like the image below.

This diagram above is what we will be referencing throughout this article. Well the first thing that we want to do is to connect to the switch. For a brand new switch the best option is to use a console cable connected to the serial port of a laptop. Pretty much all Cisco equipment comes with a console cable and all equipment comes with a console port. Simply plug the RJ45 end of the console cable into the sonsole port on the switch and the serial end into your laptop. Once that is done you can launch hyperterm.exe on your laptop. Set Hyperterm to look at what ever serial port you are plugged into and default speed setting normally work just fine. In case you want them, they are 9600, 8, N, 1.

Now you are connected to the switch and you will probably be at a prompt similar to this.

 Cisco3550>en Cisco3550#

As you can see we got the inition promtp of Cisco3550> and then I entered the command “en” which put you into enable mode. One cool thing about Cisco switches and pretty much any cisco equipment is that you don’t have to type the entire command for it to be executed. You only have to type enough that the command can only be one thing. Now lets take a look at the help menu on this switch.

 Cisco3550#>? Exec commands: <1-99> Session number to resume access-enable Create a temporary Access-List entry access-template Create a temporary Access-List entry archive manage archive files cd Change current directory clear Reset functions clock Manage the system clock cns CNS agents configure Enter configuration mode connect Open a terminal connection copy Copy from one file to another debug Debugging functions (see also 'undebug') delete Delete a file dir List files on a filesystem disable Turn off privileged commands disconnect Disconnect an existing network connection dot1x Dot1x Exec Commands enable Turn on privileged commands erase Erase a filesystem exit Exit from the EXEC format Format a filesystem fsck Fsck a filesystem help Description of the interactive help system lock Lock the terminal login Log in as a particular user logout Exit from the EXEC mkdir Create new directory more Display the contents of a file name-connection Name an existing network connection no Disable debugging functions ping Send echo messages pwd Display current working directory rcommand Run command on remote switch reload Halt and perform a cold restart rename Rename a file resume Resume an active network connection rmdir Remove existing directory rsh Execute a remote command rtr RTR Exec Configuration send Send a message to other tty lines set Set system parameter (not config) setup Run the SETUP command facility show Show running system information ssh Open a secure shell client connection systat Display information about terminal lines telnet Open a telnet connection terminal Set terminal line parameters test Test subsystems, memory, and interfaces traceroute Trace route to destination tunnel Open a tunnel connection udld UDLD protocol commands undebug Disable debugging functions (see also 'debug') verify Verify a file vlan Configure VLAN parameters vmps VMPS actions vtp Configure global VTP state where List active connections write Write running configuration to memory, network, or terminal Cisco3550#

By just typing ? you will be shown the menu of possible commands you can type. This menu is extremly helpful when trying to remember a specific configuration command. By typing the first letter of a word and following it with a ? will give you all the possible options.

 Cisco3550#s? *s=show send set setup show ssh systat Cisco3550#

As you can see the help menu show us all the possibe commands that start with S. Now this help menu can even go further than this.

 Cisco3550#show access-lists List access lists accounting Accounting data for active sessions adjacency Adjacent nodes aliases Display alias commands arp ARP table auto Show Automation Template boot show boot attributes buffers Buffer pool statistics cdp CDP information cef Cisco Express Forwarding class-map Show QoS Class Map clock Display the system clock cluster Cluster information cns CNS agents configuration Contents of Non-Volatile memory controllers Interface controller status crypto Encryption module debugging State of each debugging option dhcp Dynamic Host Configuration Protocol status dot1q-tunnel Display dot1q tunnel ports dot1x Dot1x information dtp DTP information env Environmental facilities errdisable Error disable etherchannel EtherChannel information exception exception informations file Show filesystem information flash: display information about flash: file system flowcontrol show flow control information fm Feature Manager Information forward Show forwarding info history Display the session command history hosts IP domain-name, lookup style, nameservers, and host table html HTML helper commands idb List of Hardware Interface Descriptor Blocks interfaces Interface status and configuration inventory Show the physical inventory ip IP information kerberos Show Kerberos Values key Key information l2protocol-tunnel Tunnel ports l2tcam Show L2TCAM Manager tables l3tcam Show L3TCAM Manager tables lacp Port channel information line TTY line information location Display the system location logging Show the contents of logging buffers mac MAC configuration mac-address-table MAC forwarding table memory Memory statistics mls Show MultiLayer Switching information monitor Show a SPAN session mvr Show mvr global parameters ntp Network time protocol pagp Port channel information parser Show parser commands platform Platform-specific show commands pm Show Port Manager commands policy-map Show QoS Policy Map port-security Show secure port information post Show the results of the system POST power Switch Power privilege Show current privilege level processes Active process statistics protocols Active network routing protocols queue Show queue contents queueing Show queueing configuration radius Shows radius information region Region Manager Status registry Function registry information reload Scheduled reload information rhosts Remote-host+user equivalences rmon rmon statistics route-map route-map information rtr Response Time Reporter (RTR) running-config Current operating configuration sdm Switch database management templates sessions Information about Telnet connections setup Show express setup settings snmp snmp statistics spanning-tree Spanning tree topology ssh Status of SSH server connections stacks Process stack utilization standby Hot Standby Router Protocol (HSRP) information startup-config Contents of startup configuration storm-control Show packet storm control configuration subsys Show subsystem information system Show the system configuration tacacs Shows tacacs+ server statistics tcam TCAM Information tcp Status of TCP connections tech-support Show system information for Tech-Support template Template information terminal Display terminal configuration parameters time-range Time range udld UDLD information users Display information about terminal lines version System hardware and software status vlan VTP VLAN status vmps VMPS version information vtp VTP information Cisco3550#Show

The help menu is now giving us all the different commands we can type after the show command. This help menu can take you all the way through a specific command and the syntax of it.

Now that you are somewhat familier with the CLI I will continue on view the switch configuration. Once you have connected to the switch and enterend enable (remember the EN command) enter the command show run and the running configuration of the switch will begin to display on the screen. One important thing to remember about the switch config is that there are two different configs stored on Cisco switches, the Running Conig and the Startup Config. The Running Config is the configuration that is currently running on the switch and when you make a change to the switch you are making changes to the running config. The Startup Config is the config that runs when the switch has been turned on, esentially the Startup Config becomes the Running Config when you reboot the switch. If you make changes to a switch and them reboot it, all the changes you made will be lost. That is why we have the write memory (or wr mem for short). This command will take the Running Config and write it to the Startup Config, so if the switch was rebooted you would save all of your configurations.

We talked about enable mode (EN) now lets talk about configuration mode. Configuration Mode is the mode you will enter to make most of your changes. To enter configuration mode you are going to type configure terminal or conf t for short. You will know that you are configuration mode because the prompt will change from Cisco3550# to Cicsco3550(config)#.

Now lets say based on the diagram above we want to configure a port on the switch for the computer on the left and lets say we are going to plug the computer into port number one on the switch. cisco switches normally label their ports by type of connection, layer, and then port. So F0/1 will be Fastethernet, layer 0, port 1. So lets configure F0/1 port and then discuss what we did.

 Cisco3550#configure terminal Cisco3550(config)#interface F0/1 Cisco3550(config-if)#Description John's Computer Far Left Cisco3550(config-if)#Speed 100 Cisco3550(config-if)#duplex full Cisco3550(config-if)#^Z Cisco3550#Write Memory Building configuration... [OK] Cisco3550#show running-config interface F0/1 Building Configuration... Current configuration : 202 bytes ! interface FastEthernet0/1 description John's Computer Far Left speed 100 duplex full end Cisco3550#exit

Now lets step through what we configured, first I did configure terminal to get into Configuration Mode. Next I need to specify what I am going to be configuring so I enter the command interface F0/1 which tells the switch which physical port I will be configuring. 5 years from now when I am looking back at this switch (assuming its still there) I am going to want to know what port F0/1 is connected to so I will add a description field to the port. Simply do this be typing Description (or Desc for short) and then type anything you want afterwards. The switch will save what you type and display it as a description whenever you or someone else looks at the specific port from a configuration stantpoint. I am making the assumption that everyone knows the difference between 100mps and 10mps, simply one is faster than the other. I am also making the assumption that everyone knows the different between half and full duplex. Half duplex is one way communication, only on thing can be talking at a time similar to a walkie talkie. Full duplex is two way communications where both devices can be talking to each other at the same time similar to a telephone. As you may have guessed the command speed 100 sets the speed of the port to 100 and likewise duplex full sets the duplex of the port full. The ^Z that you see there is actually a ctrl+Z key combination that is used to exit configuration mode. Then I promptly did a Write memory command so that I wouldn’t lose my configuration if the switch happens to reboot. Now I want to check and see if my configuration actually took place on the port so I am going to type show running-config interfacer F0/1 and all configuration that has been done for interface F0/1 will show up on screen and we see that everything that I configured is still there. I have successfully configured interface F0/1 for the computer on the far left, all he has to do now is plug into it.

This has been a very basic article about configuring Cisco switches. This is just the tip of the ice berg when it comes to configuring Cisco switches, but for a basic article I think we have covered a good amount. Please read my other Cisco articles for more indepth coverage of different concepts and practical applications using Cisco equipment.

If this topic really interests you please check out the following links for Cisco simulators.

Cisco Website
CCNA Simulator
TechExams.Net
SemSim.com
CertExams.com

Thanks for reading.
Mike walton