Interface and cable issues |collisions, errors, duplex, speed mismatch| explained |CCNA 200-301

In this session we will look at INterface and cable issues (collisions, errors, mismatch duplex, and/or speed) and more unusual cases in which the interface is working but not working well, as revealed by different interface status codes and statistics.
Cisco switches actually use two different sets of interface status codes-
one set of two codes (words) that use the same conventions as do router interface status codes,
and another set with a single code (word).
Both sets of status codes can determine whether an interface is working.
The switch show interfaces and show interfaces description commands list the two-code status named the line status and protocol status.
The line status generally refers to whether Layer 1 is working, with protocol status generally referring to whether Layer 2 is working.
the show interfaces status command lists a single-word state
The single-code interface status corresponds to different combinations of the traditional two-code interface status codes and can be easily correlated to those codes.
Such as connected state for working interfaces,
If you see the line status as admin down and protocol status as down or if the interface status is disabled then the likely cause is the shutdown command is configured under the interface.
If you see the line status as down and protocol status as down or if the interface status is not connect state then the likely cause is there is No cable; bad cable; wrong cable pinouts; speed mismatch; neighboring device is (a) powered off, (b) shutdown, or (c) error disabled.
If you see the line status as down and protocol status as down(err-disabled or if the interface status is err-disabled then the likely cause is the Port security has disabled the interface.
If you see the line status as up and protocol status as up or if the interface status is connected then the interface is working normal.
Next lets have a look at Interface Speed and Duplex Issues To understand some of the speed and duplex issues, lets have a look at the output from the show interfaces status and show interfaces commands
show interfaces status lists a one-line summary of the interface status and tells us more about auto-negotiation.
show interfaces gives many details but not much about autonegotiation
the show interfaces status command implies how the switch determined the speed and duplex settings.
The command output lists autonegotiated settings with a prefix of a-
and the manually set values without the a- prefix.
Some of the Common Layer 1 Problems on Working Interfaces
When the interface reaches the connect (up/up) state, the switch considers the interface to be working.
and at the same time, the switch keeps various interface counters.
These interface counters can help identify problems that can occur even though the interface is in a connect state, like issues related to the duplex mismatch problem
Whenever the physical transmission has problems, the receiving device might receive a frame whose bits have changed values.
Lets look at some of the known counters and errors in brief
Runts: are Frames that did not meet the minimum frame size requirement (64 bytes) and Can be caused by collisions.
Giants: are Frames that exceed the maximum frame size requirement (1518 bytes)
Input Errors: A total of many counters, including runts, giants, no buffer, CRC, frame, overrun, and ignored counts.
CRC: This counter increases if it Receives frame that did not pass the FCS math; can be caused by collisions.These frames do not pass the error detection logic as implemented in the FCS field in the Ethernet trailer,
Frame: This counter increase when it Receives frames that have an illegal format.Packets Output: this counter counts Total number of packets (frames) forwarded out the interface.
Output Errors: this counter counts Total number of packets (frames) that the switch port tried to transmit, but for which some problem occurred.
Collisions: this counter couts all collisions that occur when the interface is transmitting a frame.
Thats it for this session i hope this was helpful for you and please do feel free to ask any questions through email or comments.
In my next session we will have a discussion between TCP and UDP.
Thank you for watching please do like share and subscribe and hit the bell icon.
#ccna #interface #cable #issues

[@Oomtet]

This was really awesome thank you..I always come back to this video to understand more troubleshooting skills...

[@NetworkBruh]

Excellent tutorial... This is exactly how I explained it. I also used Wendell Odoms book too!

[@alandanilomc]

Muito boa a explicação. Com uma ilustração excelente! Parabéns e obrigado por compartilhar!

[@raghdajar3186]

I'm watting for the next videos.. Excellent and informative explanation.. 👋👍

[@networkingwithh4716]

Thanks 🙏🏻.. I will be uploading next video soon..

[@MahmoudMohamed-si3by]

Perfect

[@user-wb5vh1kg6b]

Somebody love Wendell Odom...

[@networkingwithh4716]

I know what you mean..

[@troysipple2591]

Good

[@networkingwithh4716]

Thanks

[@non2614]

please more detail about runs ang giants plz

[@networkingwithh4716]

Please share me your email address..

[@non2614]

@@networkingwithh4716 akurd255 @gmail.com and if you have telegram this is my number 07515886223

[@muhari776]

i have a problem with my line protocol. it show "line protocol is down (disabled). i did shutdown and no shutdown, and nothing happen. im also change the duplex and the speed to auto, but it still disabled. please help me

[@networkingwithh4716]

can you please explain the topology and share the show running config interface output

[@muhari776]

@@networkingwithh4716 Thank you very much for replying my comment. but im already solve it. my line protocol problem is the duplex. it seem that it need to be half to be up again. first time i watch your video i was really confused, and because that im not watch it properly. but after watch it again i can solve it. thank you very much, your video really help me.

[@networkingwithh4716]

@@muhari776 you are most welcome brother.

[@MrProTV]

this is copy paste from wendell odom ccna book page167 ch7 hahaha