Common Show Commands - Cisco IOs

The Show commands display important information about the configuration and operation of the device in the Cisco IOs command Line Interface (CLI) mode. Network administrators use different show commands to examine device status; interfaces, process and configuration files to validate the device operational status. The status of almost all process and function of the router can be view and verify using show command. The important show commands of Cisco IOS are the following:-

• show version
• show running-config
• show arp
• show interfaces
• show protocols
• show ip protocols
• show ip route
• show ip interface brief
• show cdp neighbors

show version

The show version command on Cisco router displays hardware information. The command output gives insight into the routers capabilities. This command can be abbreviated sh ver. The output of show version command consist of following unique information:-

• IOS version
• Image filename
• System uptime
• Type of processor
• Amount of RAM
• Number of ports on the switch
• Amount of flash memory
• Current configuration register

The figure below illustrates the output of the show version command on the Cisco router.

Show running-config

This command is used to display the configuration information currently running on the terminal. We can also use this command in combination with the show startup-config command to compare the information in running memory to the information stored in NVRAM or in a place specified by the CONFIG_FILE. This command can be abbreviated sh ru

show arp

This command displays the ARP table of the router. The ARP table is the table which contains the resolved IPv4 address to MAC address mappings. If a host is can't ping? Make sure using the show arp command that you're getting an arp entry of the host that you want to ping. The command can be abbreviated sh ar .

show interfaces

The show interface command displays all type of interfaces with configuration and statistics. It is very important for the network administrator to know what interfaces are installed and configure in the router. This command provides a lot of information in the output. This command can be abbreviated as sh int.  The figure below illustrates the output of the show interface command.

show protocols

This command displays the status of configured layer three protocols on all interfaces of the Cisco routers. This command can be abbreviated as sh prot

show ip route

The show ip route command is used to show the routing table of the router. The routing table is the list of all networks that the router can communicate; their metrics and how to communicate with them. This command can be abbreviated with sh ip ro. The command also has parameters after route (ro) like sh ip ro rip for all RIP routes. The figure below illustrates the output of the show ip route command

show ip interface brief

The show ip interface brief is one of the most frequently used commands in the Cisco devices. This command provides abbreviated output than the show ip interface command. It provides an outline of the key information for all the network interfaces on a router. The figure below illustrates the output of this command.  The output displays all interfaces on the router; the IP address assigned interfaces, if any, and the operational status of the interface. The show ip interface brief command can also be used to verify the status of the switch interfaces.

Show CDP neighbors

This command display information about the Cisco devices that are connected to your current device. Cisco Discovery Protocol (CDP) is a Cisco proprietary protocol and will only detect Cisco products. To show detailed information about neighboring devices discovered using CDP; use the show cdp neighbors command in privileged EXEC mode. The command can be abbreviated with sh cd ne.

Router interface Configuration and Verify Configuration

For Ethernet interface configuration you need to make a physical connection to the router Ethernet Interface. After establishing a connection, you can proceed with the basic configuration of Ethernet, Fast Ethernet, or Gigabit Ethernet interfaces.

Connecting To Your Router

After connecting to a router you need to get into the Global Configuration Mode  of your router using the following commands:

Router>enable Password: Router# Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)

 

The next option is to choose the correct interface. There are many different types of interfaces available on Cisco routers such as Ethernet, Fast Ethernet, Gigabit Ethernet or serial interface. All devices in current IOS versions are numbered for example.

• Gigabit Ethernet interfaces– GigabitEthernet 0/0 (G0/0) , GigabitEthernet 0/1 (G0/1)


• A serial WAN interface card (WIC) interfaces- Serial 0/0/0 (S0/0/0) and Serial 0/0/1 (S0/0/1)

For example, we want to configure FastEthernt 0/0 interface. We should enter the interface mode of  FastEthernet 0/0 using the following command.

Router(config)#interface FastEthernet 0/0

 

Adding A Description To Ethernet Interface

This feature in not necessary, you may bypass this feature. This feature providing a description about the interface and it does not assist with the configuration. It just helps prevent human error.

Router(config-if)#description Internal Interface

Setting IP Address To Interface

Now you did all prerequisites before adding IP address. Now you can add IP address to this interface.

Router(config-if)#ip address 192.168.1.1 255.255.255.0

Enabling Your Interface

Before using the router interface you need to enable the router interface. You can enable the router interface by entering the following command.

Router(config-if)#no shutdown   %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

Verifying Router Interface Configuration

There are several commands that can verify interface configuration. The show IP interface brief is the most useful command for verifying interface configuration. The output of this command display all interfaces with their IPv4 address, and their current status. The configured and connected interfaces should display a Status “up” and Protocol  “up”. Any other statements would indicate a problem with either the configuration or the cabling. Remember that show command are working in “Privileged mode”

You can also verify the configuration of interface from “show running-config”.  and Show startup-config.Another way to verify connectivity from the interface using the ping command. Ping command send five consecutive pings and measure minimal, average, and maximum round-trip times.Exclamation marks verify connectivity.

Following is the output of the show IP interface brief command, which show all three interfaces of the router. FastEthernet  0/0, status is up and protocol is up. its mean that this interface is connected to other network and protocol is up. FastEthernet status is up, it means that interface is configured and enabled with no shutdown command, its protocol is down, its mean that there is something wrong with the cable or some problem from another side. Serial 0/0/0 interface is not configured, not enabled and there is no IP address assigned to this interface.

Router#show ip interface brief Interface                     IP-Address            OK?      Method                   Status                       Protocol FastEthernet0/0     192.168.0.1            YES      manual                      up                              down FastEthernet0/1     192.168.1.1            YES     manual                      up                                up Serial0/0/0                unassigned            YES      unset          administratively down    down

Following are other commands that we can use to verify interface configuration.

• show interfaces– This command displays statistics for all interfaces on the device.


• Ping - This command generated five exclamation marks verifying connectivity to the remote side.


• show IP interface brief- Displays the IPv4 statistics for all interfaces on a router.


• Show running-config-.This command display entire configuration of the router. Here we need to see the router section in the configuration file to verify the interface configuration.


• Show startup-config:- When the configuration is saved with the write command, then configuration can be verified by the help of this command.