Common and Useful Show Commands For Cisco Devices

Posted on: April 12, 2020, by :

 

Show Commands for Cisco IOS devices

During Configuration, Operation and Troubleshooting, an Admin might have to check some parameters of CISCO devices. Those parameters checked with the help of “ show” command. Show Commands are used in Privilege mode (e.g. Router#)

if an Admin doesn’t know the exact command to check the required information, then he can take help using question mark “ ?” at the end of show .

For example:

CSSD_LAB_Router#show ?

aaa Show AAA values

access-expression List access expression

access-lists List access lists

adjacency Adjacent nodes

aliases Display alias commands

alignment Show alignment information

appfw Application Firewall information

archive Archive functions

arp ARP table

There are lots of things you can get using Show commands in cisco, but for basic fundamental help, The Chef will show some common Show commands for devices like A router or A switch.

Following show commands are explained here:

  1. show version
  2. show inventory
  3. show flash:
  4. show running-config or show startup-config
  5. show interface interface_id
  6. show ip interface brief
  7. show interface description
  8. show interface status
  9. show running-config [interface-id]
  10. show interface trunk
  11. show vlan brief
  12. show users
  13. show arp
  14. show ip route
  15. show ip protocols
  16. show cdp neighbors
  17. show cdp neighbors detail
  18. show history

Note: Router and Switch has same commands to check the common parameters.

Show Version:Show Version command will show the device’s information such as Size of RAM, FLASH, Total Interfaces, PID, Serial Number, Software Version and revision number, IOS location, License information The command shows same output for both Switch router and Firewall. The command is the following:

CSSD_LAB_ROUTER# Show Version

Note: There is another command “ show Hardware”. This command also shows the similar output of show version.

Show Inventory: show inventory command shows the output of the device’s hardware component information . This command is very useful to check Product ID(PID),Serial ,Description of Modules such as Network interface Module (NIM), Chessis, SFP modules, AC power Supply Unit etc. Captured Output is given below:

Note: there is another similar command “ show module” which is used to check the detail information regarding the modules connected to the device.

Read More: How To Set Up A Wireless Router

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Show Flash:This command is used to check the Flash of a cisco device. Cisco Device IOS image is stored in the flash. To check the Image name,location , available free space, storing configuration file, vlan database file etc. ,we check the device’s Flash using “show flash:” command. Please note that there is a “:” at the end of the command.

Note: Switch# diris another command shows the similar output.

Show Running-config and show startup-config:Device is operated from ram and ram generates a configuration file. This Configuration file is called Running-config file. When we save the configuration file RAM copies the running-config file to NV-RAM and name it as Startup-config. So as a usual behavior of RAM, when device is restarted all unsaved data will be lost.

Output of the Show Running-Config is given below. Note: Startup config will be similar.

Show interface Inteface_ID:[example : show interface gigabitethernet 0/0] this command is used to check the detail information of an interface. Mac-address , State, IP address etc are captured from this output.

Show ip interface brief:this command is used to check the interface summary such as if the interface is active or not , IP address assigned to the interface etc. this is a very useful command and mostly used for basic troubleshoot to check interface functionality status.

Show interface description:this command Is used to check the interface status and description . This command doesn’t show the IP address assigned to the interface.

Show interface status:this command is used to check the interface physical status like if the interface is plugged with cable or not, Interface Speed, Duplex , Type etc.

Show running-config interface Interface_ID[e.g. show running-config interface G0/0] :this command is used to filter out the interface information from the running-config file. This is also another useful command to check the interface configuration in running-config file.

Show interface trunk:This is a command commonly used in Switches to check the trunk ports. The command captures and show all the trunk interfaces information such as encapsulation type, Native vlan, Allowed vlan, vlan pruning etc.

Show vlan brief:this command is used to check all the vlan from vlan database. The output shows the list of vlan, vlan name, VLAN port membership and vlan functionality status.

Please note that Vlan 1, and Vlan 1002 to 1005 are default configured vlan. These vlan can not be deleted.

Show users :this command is used to check which Users are currently logged in the device and also User’s IP address.

Show arp:Show ARP(address resolution protocol) shows the IP to mac-address mapping in Layer 2. And also shows the Interface ID using which the IP and MAC is being received.

Show IP route:This command shows all the routes available in the routing Table of a Layer 3 device. Show ip route shows lots of information like route is received by which interface, routing protocol used etc.

IN routing table, the Networks which are created in router’s interface will be declared as Directly Connected network and the Code is “C”. Default Route is a special route and its Code is “S*”. The Code list for the Route types is also mentioned in the routing table.

you can apply filter to the show ip route command to get specific route’s availability :

show ip route connected

will show the connected routes only show ip route static

will show the static routes only show ip route ospf

will show the connected routes only show ip route eigrp

will show the connected routes only show ip route rip

will show the rip routes only show ip route [Network/host Address] [Subnet Mask] for example:

Show ip route 192.168.1.0 255.255.255.0

Will show only the route for 192.168.1.0 255.255.255.0 network

Show IP protocols:Show ip protocol shows the configured dynamic routing protocol information. Like the Process ID, network which are being broadcast or Multicast, AD value etc.  this output was taken from a LAB setup.

Show CDP Neighbor:Show cdp neighbor shows a layer 2 topology. This is a very useful command and this command is cisco proprietary. Cisco has developed this protocol. Show CDP neighbor command shows How the remote devices are directly connected with the source device[the device from where we are applying the command]. Beside those, CDP protocol also fetch the remote device information such as device Model No, hostname,device type ,Local interface and outgoing interface

Example:in Core Router the chef has applied the configuration show cdp neighborto check how the remote devices are connected to the Core-RTR

Note: we are applying command “show cdp neighbor” in CORE-RTR. Local Interface means CORE-RTR’s interface. outgoing interface (Port ID) is the information of remote devices.

Show CDP neighbor detail :this command shows the detail information of remote devices. For example show cdp neighbor detail shows the output like Remote device IP address, Software Version, Source Router’s Port ID and Remote router’s Port ID,Hostname etc.

Show history:This command is used to check the history of the show commands. And “ Show history all” command is used to see the logs of the commands applied.

CSSD_LAB_Router#show history
show history
show running-config
show ip interface brief
show inventory
conf t
show history
CSSD_LAB_Router#

Read More: Step-by-step Guide to Configure and Setup Home or Office Routers

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