Switch 9300 / One port failure > No uplink, no log > How to fix it ?

[Elrick Landon]

Hi to all,

I have Cisco Switch WS-C9300-48P-E, port 19 on this switch doesn't work, if i connect a device on this port (POE device or not), no uplink, no reaction from Cisco panel, no notification into console... so i dunno how to fix this issue.

Port setup sound good as other, so no reason... 

How can make more investigation to knowing if it's a port failure please?

Best Regards.

[Leo Laohoo]

What is the exact firmware of the switch?

What is the uptime of the switch?

If the device is moved to, say, port 36, does the link light up?

[Elrick Landon]

Firmware  = Amsterdam-17.3.7

1 Week at this time, already restarted, but same issue.

If i moved device to another port it works fine, uplink is appear in yellow and green some few seconds after.

[Leo Laohoo]

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@Elrick Landon wrote:

If i moved device to another port it works fine, uplink is appear in yellow and green some few seconds after.

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In our place of work, we call it "ghost ports". 

This behaviour is very common with switches loaded with IOS-XE.  The "fix" is not to reload the switch but to remove the power supplies.

Please post the complete output to the command "sh post".

[Elrick Landon]

[Leo Laohoo]

Perfect.  This eliminates hardware failure.  

The only culprit left on the table is "ghost ports". 

I also notice that this is a PoE capable switch.  This actually helps because ghost ports are very common with the following combination:  PoE-capable switch and IOS-XE.  

This is because of a hardware design "bug" called MOSFET which affects all Cisco Catalyst PoE switches that run on IOS-XE, starting from 3650/3850 and extends all the way up to all Catalyst 9k switches.  The Bug IDs are:  CSCvd46008 & CSCvj76259

The only workaround is a cold-hard reboot:  Remove the all the power supplies until the power supplies stop screaming.  This will force the electrical component a "hard reset" and restore itself.  IF the same issue, after a cold-hard reboot, are still occurring (different ports this time), RMA the switch.