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In this lesson,

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we're going to discuss interface issues.

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When we talk about an interface issue,

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we're really focused on any problems

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in the network's interface operation

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that can impact your data transmissions

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and network performance.

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These interface issues can significantly affect

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your network's performance and reliability as well,

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so it's important to understand

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how you can best troubleshoot

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and remediate these different kinds of interface issues.

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Interface issues include things

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like increasing interface counters

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for cyclic redundancy check errors, runts,

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giants and drops,

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as well as issues with various port statuses,

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including the error disabled,

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administratively down, and suspended port statuses.

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First, we have increasing interface counters

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that are associated with cyclic redundancy errors.

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A cyclical redundancy error or CRC error is any error

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that occurs when the check of a data's block integrity

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upon reception doesn't match the check sum value

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that was attached during the transmission.

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Now, when this occurs,

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this indicates that the actual data

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has been corrupted or altered

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during the transmission from one device to another.

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Whenever you see increasing numbers of CRC errors,

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this can indicate that there is a noise,

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interference, or other physical issue

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that's affecting your network connectivity.

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These CRC errors can occur whenever the frame's check sum

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doesn't match the check sum that's calculated upon arrival

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for that data frame.

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So if you see a high number of CRC errors in your network,

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this usually is going to indicate that there's an issue

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related to the electrical interference, cable damage,

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or a hardware fault inside of your network

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or your network devices.

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Second, we have increasing interface counters

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associated with runts.

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Now, runts are frames that are smaller

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than the minimum frame size used by your network.

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A runt is going to be created whenever there's a collision

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or other disruption that occurs

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during your packet transmissions on your network,

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but they can also be indicative of a deeper network issue

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that you may need to diagnose and resolve.

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When I've experienced these type of runts in the past,

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it's normally going to be caused by a problem

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like a network card malfunction,

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using a collision domain that's too large,

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or simply being a cabling issue

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that may need your attention.

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For these reasons,

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it's essential that you monitor your network traffic

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to identify and address the root cause of any runt frames

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that you see in order to maintain the integrity

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and performance levels associated with your network.

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Third, we have an increasing interface counter

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associated with giants.

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Now, giants are going to refer to any frames

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that exceed the maximum frame size of your network.

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A giant is often created due to a misconfiguration

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or the malfunctioning of a network device.

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Now, because a giant is so much larger

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than the expected frame size on your network,

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a giant can cause network traffic congestion,

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which can lead to poor performance inside of your networks.

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To prevent these kinds of congestions,

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many network devices are going to be configured

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to simply drop any frames

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that are larger than the maximum frame size setting

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for your particular network.

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If this happens,

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you're going to see the number of giants increase

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and the number of drop frames also increase

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in a direct linear relationship.

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Like runts, you should always monitor your network traffic

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to identify and address the root cause of any giant frames

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that you may find on your network.

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Fourth, we have the increasing interface counters

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that are associated with drops.

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Now, drops occur when the device's buffer is full

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and it can't accommodate incoming frames or packets anymore.

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This kind of dropping can lead to the packet

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simply being discarded by your network device

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because it's becoming too overloaded or overwhelmed,

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and therefore it's unable to process

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any new incoming frames.

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Now, drops usually occur

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whenever a high level of network traffic

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is being experienced by a device,

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or if the network device is operating

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beyond its normal operating capacity limits.

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If you see fairly persistent drop rates inside your network,

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this will significantly affect the data flow

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and the network efficiency that you can achieve,

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so it is important that you set up monitoring

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to identify and address any underlying issues,

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such as bandwidth bottlenecks,

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inefficient traffic management,

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or to determine if

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inadequate hardware resources are available.

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Fifth, we have the issue associated

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with an error disabled port status.

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Now, a port status of error disabled

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is going to be used to indicate

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that a port on a switch has been automatically shut down

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by the network system itself

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because of a network error or a violation in policy.

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For example, if a port starts to experience

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a bridge protocol data unit guard violation,

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that switch can proactively disable the port

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to prevent possible network loops from occurring.

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Then it can require that you perform a manual intervention

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or that you utilize specific configuration commands

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to re-enable the port for normal operations once more.

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Six, we have the issues associated

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with an administratively down port status.

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Now, an administratively down port status

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is going to signify that a network port

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has been intentionally disabled

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by your network administrators

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and that the port was not disabled

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due to some kind of error or network issue.

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For example, your network administrator

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may have chosen to shut down a port to perform an upgrade,

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or to modify the settings on that port.

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In this type of scenario,

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the port status will be reflected as administratively down

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because this indicates that a deliberate,

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not an error induced deactivation of that port has occurred.

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Now, to return an administratively down port

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back to normal operations, again,

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you simply need to issue a specific command

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within the network device's interface configuration mode.

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If you're using a Cisco based device, for example,

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you're going to use the command no shutdown.

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to reverse the administrative down status

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and re-enable the port

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for normal traffic flow in operations.

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Before you activate the port using the no shutdown command,

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you should first ensure

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that the port is ready to be reactivated

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and that all the necessary maintenance and configurations

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have been completed properly to avoid any potential issues

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once that port is reactivated

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and back in normal operational use.

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Seventh and finally,

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we have the issues associated with a suspended port status.

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Now, a suspended port status is normally going to indicate

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when there's a violation of an established protocol

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or policy within your network.

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For example, if there is an ether channel misconfiguration

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on your network switch port,

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that network switch port will automatically be placed

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into a suspended port status.

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Basically, anytime the network determines

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that a port has the potential

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to cause a data transmission error or a network loop,

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that switch port will be put into a suspended port status

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until the switch port's configuration issue gets resolved

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and its protocols are realigned.

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Typically, a suspended port status

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is going to be used in a port channel configuration

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whenever a violation of the channeling protocol

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is going to occur.

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To solve a suspended port status issue,

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you need to resolve the underlying configuration issue

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on that switch port first to be able to ensure

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it's consistently and correctly configured

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for ongoing operational use.

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So, remember, interface issues are defined

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as any problems in the network's interface operation

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that could impact your data transmission

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and network performance.

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Interface issues include things

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such as increasing interface counters

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for cyclic redundancy check errors,

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runts, giants, and drops,

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as well as any issues with various port statuses,

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like the error disabled,

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administratively down, and suspended port statuses.

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By learning how to best troubleshoot

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and remediate the different kinds of interface issues,

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you can drastically increase the performance

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and reliability of your networks.