C9300-48S switchport problem

[ptothhu]

Hello Everyone,

This is the situation:

We recently upgraded some C9300-48S stacks to IOS 17.9.4. No other physical or logical change was made on the network.

Symptoms:

After the upgrade, the ports are selectively down/down. The devices connected are desktop PCs and printers.

The connection is 1GB via MM fiber. There is visible red light from both sides (PC NIC card, fiber cable, and SFPs in the switch). However, the port status is mostly down/down (indicating a L1 issue).

The stacks in question have been rebooted, but no change. What could be the problem?

Regards,

Peter

[paul driver]

Hello
Possible bug -here

[ptothhu]

Thanks, Paul, but that's not the case. Your link shows possible solutions for PoE switches.

Mine is an SFP switch with FO connections. They don't have PoE features.

[paul driver]

Hello
Yes understand--bbut as it the same ios version and same switch model I just wondering if it could be effecting your ports - have you tried downgrading or even upgrading once more?

[marce1000]

  - Check logs on the switch (and or stack) for starters ,

 M.

[marce1000]

 - Also when encountering such issues , always use latest advisory :
          https://software.cisco.com/download/home/286322252/type/282046477/release/Dublin-17.12.4

 M.

[Joshqun Ismayilov]

@ptothhu 

Did you check ROMMON version  ?  or did you Upgrade it also? 

Please check links :
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17-9/release_notes/ol-17-9-9300/upgrading_the_switch_software.html

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17-9/release_notes/ol-17-9-9300/rommon_versions.html#rommon-versions

Thanks!

[Leo Laohoo]

Power down the switch, pull the power supplies out and wait for the power supplie's fans to stop spinning. 

Put the power supplies back in and energize the switch/stack.

[ptothhu · Accepted solution]

After some testing, investigation and trials by error, it turned out that the solution was relatively simple. This is the missing line from the config:

speed nonegotiate

After adding this line to the switch port config, all the connections to the various devices were reestablished and have worked correctly ever since.

Thank you for all your contributions and valuable advice. Those inputs helped a lot in narrowing down the real problem.

Regards,

Peter