If you are preparing for your CCNA exam, you probably know about the simulation questions that Cisco will throw are you. These simulation questions are going to be some of the most difficult and intimidating questions on the whole exam. Instead of choosing a multiple choice answer, you will be forced to type in commands and interact with a network the same way you would in the real world.
Luckily, Cisco does not make these simulation questions are difficult as they could. When I was studying for my CCNA I was expecting the simulation questions to ask me to configure a router or something similarly difficult. Instead, most of the questions were actually on debugging existing configurations. What I had to do was look through an existing router and/or switch configuration and figure out what was wrong with the configuration and why device A could not reach device B.
Because these questions are mostly based on troubleshooting existing configurations, the most important CCNA commands are different types of ‘show’ commands. The CCNA exam can be time consuming, and you must know what information each show command will display. You cannot afford to sit around trying to find the information you need during the simulation questions. You must know all the show commands so you can quickly find the errors that the CCNA questions are asking you to find.
The following is a list of the top CCNA show commands that you will have to know to do well on the exam.
?
The question mark does function on the CCNA simulation questions. This is one of the most useful commands on Cisco devices. When you use the question mark, it shows you the possible commands you can run at that point. You can type a partial command and then use the question mark to see what your options are for completing the command. This is great if you cannot remember what parameters a command takes, or even the order of the parameters. For example “show ip ?” will give you a list of what you can run to complete the “show ip XXX” command.
If you get stuck on a CCNA simulation question and need some help, use the question mark to give you a hint. If you are having trouble remember all the show commands you can try, type in “show ?” and the Cisco software will help you.
show running-configuration
This command shows the device’s current configuration. This is the configuration that is currently running in the memory, which is not necessarily the same configuration as the device will have upon a reboot.
This command will give you more details about how the device is currently configured than any other show command. When you are in doubt, try this command. There is a good chance that it will display what you are looking for.
To save the current configuration you must type ” copy running-configuration startup-configuration”
show ip interface
As you know, the IP protocol takes place on the third layer of the OSI model. This command shows you the layer 3 information for an interface on the device you are looking at. This includes the IP address, network mask along with the layer2 and layer 3 status.
To look at a specific interface you would add the interface to the end of the command: “show ip int fa 0/3”.
show interface
This command displays the status of the interfaces on a device. You can run it as “show int” to show all the interfaces or you can specify a certain interface by running “show int fa 0/3” of whatever.
This command has very detailed information about each interface and is great for troubleshooting when you think there might be a problem on a specific interface. This can include MTU mismatches, Errors on the interface, the status of the interface, etc.
‘show ip interface brief’
This is a quick command to run when starting to troubleshoot. It will give you a rundown of the interfaces and let you know which interfaces are currently down. As the command implies, it is a brief summary of the interfaces on the device.
show ip route
This is a layer 3 command showing you details on the routing table of a router. A router’s main job is to route traffic to it’s destination. To do this, the router has a table of different destination IP blocks and how to get to each of them. A router knows which interface to send traffic out of. This information is kept in a routing table.
The “show ip route” command is used to look up the information in the routing table. This allows you to confirm that a router does know where to send traffic for a certain destination. It also allows you to confirm that the router is sending traffic our of the correct interfaces. This information includes how the router learned about those destinations (OSPF, static route, etc.)
show vlan
This command will display vlan information, including which vlan is set on which interface. If you ever come across a question where one side is part of a vlan, use this command to make sure the other end of the connection is also set to allow traffic from the same vlan.
show access-list
The show access list command shows you all the access lists on the device. If you are interested only in the IPv4 access lists you can type “show ip access-list”. For IPv6 access lists you can type “show ipv6 access-list”.
Note that this command does not tell you which interface each of the access lists is actually applied to. To see the access lists along with the interfaces that the access lists are applied to, run “show running-config”.
With these commands you should be able to ace the simulation questions on the CCNA exam.
