Cisco IOS Commands – Using The Show Interface Cisco IOS Command For Troubleshooting Network Issues
by Francis Teo on August 29, 2009
in Cisco IOS Commands
Mastery of Cisco IOS commands is a very important part of the CCNA test and is also essential for anybody who is serious about a career in computer networks. Of all the commands, the most crucial are those you should have at the tips of your fingers when something goes wrong and you are suddenly called upon to troubleshoot. Every so often, the issue is related to a switchport and it is important to know how to use the show interface Cisco IOS command properly. If there is a network issue regarding slowness or disconnects, here are a 6 things you should be looking at when you check on the output of the “show interface” Cisco IOS command:
1. Is the physical port and line protocol up? If you don’t have layer 1 and layer 2 connectivity, there is no way any IP packet is going through this port.
2. Any duplex mismatch issues? Duplex mismatch could lead to slowness and errors in the network. If the speed does not match, the port won’t even come up.
3. Any QoS drops? If you have a QoS policy in place, it might be shaping and policing the traffic and dropping the packets. In this case, you might need to either rework your QoS policies, or advise the user about the high traffic levels.
4. What are the traffic levels, is this normal? You can check the input and output rates to see if this is normal for this time of day.
5. Any CRC or other input errors? Input and CRC errors could signify a physical problem with the port or cabling.
6. Any output errors or collisions? Output errors could also indicate a physical issue with the port or cabling. A full-duplex connection should have no collisions while it is quite normal for a half-duplex port to have collisions.
Cheers,
Francis (SavvyNetCert.Com)
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