Which Cisco IOS command would produce the following output?
A. show ip interface
B. show ip interface brief
C. show interfaces
D. show interface brief
Correct Answer: C
The output given in the question is produced with the show interfaces command. This command is used to view the statistics for the configured interfaces on the router. From the
sample output, we can determine the following facts:
The interface has not been enabled, as indicated by the first line Serial0/0/0 is administratively down. It is not ready to for to forward packets. To enable it, the no shutdown
command should be entered.
Line 3 shows that the subnet mask is 255.255.255.0.
Line 3 shows that the IP address is 184.108.40.206, a public IP address.
Line 6 shows that the encapsulation is HDLC, which is the default.
The interface is NOT connected to a LAN, because it is a serial interface.
Two fields worth mentioning in the output of the show interfaces command are the no buffer and the ignored fields. The ignored field shows the number of received packets ignored by
the interface because the interface hardware ran low on internal buffers. The no buffer field shows the number of received packets discarded because there was no buffer space in the
main system. When either of these two counters begins to increment, it could be the result of a broadcast storm.
Since the show interfaces command displays the up/down state of the interfaces, it is a good command for troubleshooting. For example, any time users cannot access a resource
that requires them to traverse a router, it is always a good idea to use show interfaces to take a quick look at the state of the interfaces. In the example diagram below, users cannot
access the resource in the network of the Acme Company from the LAN in the Ajax Company. The first step would be to execute the show interfaces command in R1 to verify
functionality of the interfaces on R1.
The show ip interface command is incorrect because this command is used to view whether the interfaces configured for Internet Protocol (IP) are usable. Following is a sample
output of the show ip interface command:
The show ip interface brief command is incorrect because this command provides an overview of all the interfaces configured for IP on the router. The following is sample output from
the show ip interface brief command. It can be quite useful for troubleshooting as well. For example, if you cannot ping the Ethernet1 interface from a host on the Ethernet 0 LAN, you
could determine from the output below that the Ethernet 1 interface is administratively down.
Router# show ip interface brief
Interface IP-Address OK? Method Status Protocol
Ethernet0 220.127.116.11 YES NVRAM up up
Ethernet1 unassigned YES unset administratively down down
Loopback0 18.104.22.168 YES NVRAM up up
Serial0 22.214.171.124 YES NVRAM up up
The solution here would be to enter configuration mode for the interface Ethernet 1 and enable it with the no shutdown command.
The show interface brief command is incorrect because this command is not a valid Cisco IOS command.
LAN Switching Fundamentals
Troubleshoot interface and cable issues (collisions, errors, duplex, speed)