Top 10 Cisco CCNA commands to know

These Cisco CCNA commands are a must for all network admins and those preparing to take the CCNA 200-301 certification! I am referring to the show…. command, which is generally used for network troubleshooting and also for finding configuration information on a router or switch.

The show…commands help you find any configuration information on a router or switch. Knowing how to use these CCNA commands is therefore essential to administer a company’s network and also to pass your CCNA 200-301 exam. From now on, there will be AMLs during associate and professional level exams. For more information, see this article on the Cisco website

Here are the top Cisco CCNA commands to know:

show running-config

The show running-config command, often abbreviated to show run, is the most commonly used command by network administrators. It provides you with the complete configuration report on a network device (router or switch).

The result of the show run command contains all configurations made on a router or switch. This can be IP address configuration information on interfaces, security information, routing protocols, VLANs, etc.

All this information helps you in troubleshooting a network and also to copy and save the configurations in a TXT file or other on your computer.

copy running-config startup-config

The copy running-config startup-config command allows you to save the configurations.

Remember that the startup configuration file, also called startup-config, is stored in the NVRAM of the device.

And the running configuration file, also called running-config is stored in RAM.

Thus, the copy running-config startup-config command copies the running-config file to the startup-config file.

The opposite, i.e. copy startup-config running-config allows to copy the startup-config file to the running configuration file.

The write command plays the same role as copy running-config startup-config! But during the test, it is not recommended to use the write command.

show interfaces

Show interfaces displays in detail all interface information of a router or switch. You can also use the shortcut sh inte to get the same results.

This command can be used to display detailed information about a specific interface, for example: show interfaces gigabitEthernet 0/0 .

show ip protocols

The show ip protocols command on a router displays the configured routing protocols and route statistics. This command is used to determine the routing protocols used on a device.

show ip route

show ip route on a router or switch L3 displays the routing table used to transmit data from one network to another.

This command will also tell you the routes learned by the L3 router or switch.

You will find in the results: directly connected routes, static routes, or routes learned by routing protocols like OSPF, EIGRP, RIP, BGP, etc.

The show ip route command is often used to identify and troubleshoot routing problems on an L3 router or switch.

Role and function of switches – CCNA 200-301 – Networks (

show cdp neighbors

The show cdp neighbors command on a Cisco router or switch displays information about Cisco devices connected to the device you are using.

It should be noted that the CDP protocol is Cisco proprietary, so it only works on Cisco equipment.

The information displayed by the command can be: the type of the equipment, its IP address, the interface connected to the neighbor, its identifier, etc.

Network administrators usually use this command to determine the neighbors of a device to discover the network topology.

show lldp neighbors

show lldp neighbors works in the same way as show cdp neighbors, except that the lldp is open, i.e. it also works on other manufacturers’ equipment. It is used to discover nearby network topologies.

LLDP is not enabled by default on Cisco devices. To enable LLDP on a Cisco device, use the lldp run command in global configuration mode.

show vlan brief

show vlan brief displays the information and status of VLANs on a device.

The results include the VLANS names, number, and interfaces assigned to the VLANs.

show interfaces trunk

To check the trunk on the different ports of a switch, use the show interfaces trunk command.

It displays the information of the VLANs authorized on each port in Trunk mode. The show interfaces trunk command only gives results if the trunk is configured on the ports of a switch.

show access-lists

The show access-lists command displays the access lists configured on a network device. If there is no list access configured on the equipment, the command does not display any results.

show ?

To go further and discover more commands, you can use ? after each command to get a list of all available options.

For example, show ? on a router gives this :

Router#show ?
 aaa Show AAA values
 access-lists List access lists
 arp Arp table
 cdp CDP information
 class-map Show QoS Class Map
 clock Display the system clock
 controllers Interface controllers status
 crypto Encryption module
 debugging State of each debugging option
 dhcp Dynamic Host Configuration Protocol status
 dot11 IEEE 802.11 show information
 file Show filesystem information
 flash: display information about flash: file system
 flow Flow information
 frame-relay Frame-Relay information
 history Display the session command history
 hosts IP domain-name, lookup style, nameservers, and host table
 interfaces Interface status and configuration
 ip IP information
 ipv6 IPv6 information
 license Show license information
 line TTY line information
 lldp LLDP information
 logging Show the contents of logging buffers
 login Display Secure Login Configurations and State
 mac-address-table MAC forwarding table
 ntp Network time protocol
 parser Show parser commands
 policy-map Show QoS Policy Map
 pppoe PPPoE information
 privilege Show current privilege level
 processes Active process statistics
 protocols Active network routing protocols
 queue Show queue contents
 queueing Show queueing configuration
 running-config Current operating configuration
 secure Show secure image and configuration archive

Press the ENTER key on your keyboard to scroll through the available options. In front of each option, a description allowing you to know the utility of the command.

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Adam Guipelbé

Ingénieur Systèmes et Réseaux

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