In this lesson,
we're going to discuss interface issues.
When we talk about an interface issue,
we're really focused on any problems
in the network's interface operation
that can impact your data transmissions
and network performance.
These interface issues can significantly affect
your network's performance and reliability as well,
so it's important to understand
how you can best troubleshoot
and remediate these different kinds of interface issues.
Interface issues include things
like increasing interface counters
for cyclic redundancy check errors, runts,
giants and drops,
as well as issues with various port statuses,
including the error disabled,
administratively down, and suspended port statuses.
First, we have increasing interface counters
that are associated with cyclic redundancy errors.
A cyclical redundancy error or CRC error is any error
that occurs when the check of a data's block integrity
upon reception doesn't match the check sum value
that was attached during the transmission.
Now, when this occurs,
this indicates that the actual data
has been corrupted or altered
during the transmission from one device to another.
Whenever you see increasing numbers of CRC errors,
this can indicate that there is a noise,
interference, or other physical issue
that's affecting your network connectivity.
These CRC errors can occur whenever the frame's check sum
doesn't match the check sum that's calculated upon arrival
for that data frame.
So if you see a high number of CRC errors in your network,
this usually is going to indicate that there's an issue
related to the electrical interference, cable damage,
or a hardware fault inside of your network
or your network devices.
Second, we have increasing interface counters
associated with runts.
Now, runts are frames that are smaller
than the minimum frame size used by your network.
A runt is going to be created whenever there's a collision
or other disruption that occurs
during your packet transmissions on your network,
but they can also be indicative of a deeper network issue
that you may need to diagnose and resolve.
When I've experienced these type of runts in the past,
it's normally going to be caused by a problem
like a network card malfunction,
using a collision domain that's too large,
or simply being a cabling issue
that may need your attention.
For these reasons,
it's essential that you monitor your network traffic
to identify and address the root cause of any runt frames
that you see in order to maintain the integrity
and performance levels associated with your network.
Third, we have an increasing interface counter
associated with giants.
Now, giants are going to refer to any frames
that exceed the maximum frame size of your network.
A giant is often created due to a misconfiguration
or the malfunctioning of a network device.
Now, because a giant is so much larger
than the expected frame size on your network,
a giant can cause network traffic congestion,
which can lead to poor performance inside of your networks.
To prevent these kinds of congestions,
many network devices are going to be configured
to simply drop any frames
that are larger than the maximum frame size setting
for your particular network.
If this happens,
you're going to see the number of giants increase
and the number of drop frames also increase
in a direct linear relationship.
Like runts, you should always monitor your network traffic
to identify and address the root cause of any giant frames
that you may find on your network.
Fourth, we have the increasing interface counters
that are associated with drops.
Now, drops occur when the device's buffer is full
and it can't accommodate incoming frames or packets anymore.
This kind of dropping can lead to the packet
simply being discarded by your network device
because it's becoming too overloaded or overwhelmed,
and therefore it's unable to process
any new incoming frames.
Now, drops usually occur
whenever a high level of network traffic
is being experienced by a device,
or if the network device is operating
beyond its normal operating capacity limits.
If you see fairly persistent drop rates inside your network,
this will significantly affect the data flow
and the network efficiency that you can achieve,
so it is important that you set up monitoring
to identify and address any underlying issues,
such as bandwidth bottlenecks,
inefficient traffic management,
or to determine if
inadequate hardware resources are available.
Fifth, we have the issue associated
with an error disabled port status.
Now, a port status of error disabled
is going to be used to indicate
that a port on a switch has been automatically shut down
by the network system itself
because of a network error or a violation in policy.
For example, if a port starts to experience
a bridge protocol data unit guard violation,
that switch can proactively disable the port
to prevent possible network loops from occurring.
Then it can require that you perform a manual intervention
or that you utilize specific configuration commands
to re-enable the port for normal operations once more.
Six, we have the issues associated
with an administratively down port status.
Now, an administratively down port status
is going to signify that a network port
has been intentionally disabled
by your network administrators
and that the port was not disabled
due to some kind of error or network issue.
For example, your network administrator
may have chosen to shut down a port to perform an upgrade,
or to modify the settings on that port.
In this type of scenario,
the port status will be reflected as administratively down
because this indicates that a deliberate,
not an error induced deactivation of that port has occurred.
Now, to return an administratively down port
back to normal operations, again,
you simply need to issue a specific command
within the network device's interface configuration mode.
If you're using a Cisco based device, for example,
you're going to use the command no shutdown.
to reverse the administrative down status
and re-enable the port
for normal traffic flow in operations.
Before you activate the port using the no shutdown command,
you should first ensure
that the port is ready to be reactivated
and that all the necessary maintenance and configurations
have been completed properly to avoid any potential issues
once that port is reactivated
and back in normal operational use.
Seventh and finally,
we have the issues associated with a suspended port status.
Now, a suspended port status is normally going to indicate
when there's a violation of an established protocol
or policy within your network.
For example, if there is an ether channel misconfiguration
on your network switch port,
that network switch port will automatically be placed
into a suspended port status.
Basically, anytime the network determines
that a port has the potential
to cause a data transmission error or a network loop,
that switch port will be put into a suspended port status
until the switch port's configuration issue gets resolved
and its protocols are realigned.
Typically, a suspended port status
is going to be used in a port channel configuration
whenever a violation of the channeling protocol
is going to occur.
To solve a suspended port status issue,
you need to resolve the underlying configuration issue
on that switch port first to be able to ensure
it's consistently and correctly configured
for ongoing operational use.
So, remember, interface issues are defined
as any problems in the network's interface operation
that could impact your data transmission
and network performance.
Interface issues include things
such as increasing interface counters
for cyclic redundancy check errors,
runts, giants, and drops,
as well as any issues with various port statuses,
like the error disabled,
administratively down, and suspended port statuses.
By learning how to best troubleshoot
and remediate the different kinds of interface issues,
you can drastically increase the performance
and reliability of your networks.