Catalyst C1200 - can't console in after configuring except on reboot

DavidL-AOCU · ‎08-27-2025

Hi,

So we have a bunch of C1200 (and a couple of C1300) series switches that we recently bought and I've configured for our setup, however I've noticed that after doing so, I can no longer console into them unless I have the cable connected to the switch while it reboots. And to be clear, it's not a matter of I can see output but can't interact, the console app actually errors on connection and cannot connect.

I'm using Putty on Windows 11 24H2 with a USB C to C cable on a Dell Latitude 5540 laptop.

When I connect the console cable with the switch already running, device manager never shows a COM port. If I reboot the switch, after a few seconds device manager will show a COM port connected. If I disconnect and reconnect the cable, the COM port goes away and does not return. When the COM port does not show, expectedly, Putty errors out and cannot connect.

I can connect to the switches via GUI and SSH just fine.

Before I configured the switches, I did not have these issues with consoling in (I could connect the cable when the switch was already running, or disconnect and reconnect the cable, and a COM port would appear in device manager every time). See edit below.

Any thoughts on what I may have done (or be doing) wrong?

I've attached an anonymized config in a txt file for reference.

Edit Aug 29th: I just tried updating the firmware to the latest release (4.1.7.17) on one of the units and I still experience the same issue.

Also, apparently I was wrong about this issue not being present when they are unconfigured? I could have sworn they worked as expected before I started configuring them, but I just tested doing a factory reset to the same one I did the firmware upgrade on and it still experiences the issue after the reset. 🫤

Jens Albrecht · ‎08-27-2025

Hello @DavidL-AOCU,

there are 2 bugs related to the console of the Catalyst 1200/1300 switches that I am aware of.
One of them (CSCwi00760) should have been fixed with the software you are running and the other one is this:

CSCwp85371
Symptom
Sometimes auto baud rate cause console hang
Workaround
Disable auto baud rate on the console.

If you boot with the console cable being connected, the baud rate is already fixed so you might be hit by this one.

Hence disable auto baud rate on the console and check again.

HTH!

DavidL-AOCU · ‎08-27-2025

Hmm, ok, thanks for the suggestion. I'll take a look on Friday when I have the next opportunity to connect to one of these and give it a try.

DavidL-AOCU · ‎08-29-2025

Ok, just had a chance to test via disabling the auto baud rate. No dice. Still does the same thing.

DavidL-AOCU · ‎08-29-2025

I just tried updating the firmware to the latest release (4.1.7.17) on one of the units and I still experience the same issue.

Also, apparently I was wrong about this issue not being present when they are unconfigured? I could have sworn they worked as expected before I started configuring them, but I just tested doing a factory reset to the same one I did the firmware upgrade on and it still experiences the issue after the reset. 🫤

Jens Albrecht · ‎08-29-2025

Well, the auto baud rate bug I mentioned above is still not fixed in 4.1.7.17.
What console speed did you set when disabling auto baud rate? 115200?

DavidL-AOCU · ‎08-29-2025

I did the update in case it was something else that may have been fixed in there. No harm in trying.

When disabling auto baud, the switch defaults to a static of 115200. I also tried setting the speed to 9600. No luck either way.

Would the baud rate even affect this, though? I would think that wouldn't come into play until attempting to make the connection. With the problem I'm having, there's no COM port even showing in device manager for me to attempt to connect on.

Jens Albrecht · ‎08-29-2025

...there's no COM port even showing in device manager

Never seen this happen. Looks like you need to open a TAC case.

DavidL-AOCU · ‎08-29-2025

I was afraid it might come to that. I'm going to try a couple more things, but opening a TAC case will have to wait until the 8th... I'll be out until then.

Julialisa · ‎08-29-2025

@DavidL-AOCU wrote:

That’s interesting, thanks for sharing all the details. Since the COM port itself isn’t even showing up in Device Manager unless the switch is rebooting with the cable already attached, it really sounds more like a driver/USB chipset interaction than just a baud rate issue. A couple of things you might want to try before going through TAC:

Test with Cisco’s USB console driver instead of relying on Windows’ built-in one (sometimes Windows assigns a generic driver that doesn’t behave consistently).
Try a USB-A to USB-C cable with a known-good USB-A port instead of C-to-C, just to rule out Dell’s USB-C controller quirks.
Check if the COM port sticks around if you disable USB selective suspend in Windows power settings.

If none of that makes a difference, then yeah, opening a TAC case is probably the way to go.

DavidL-AOCU · ‎09-09-2025

Hey, apologies, I never got notified of your post and have been on vacation since my last post.

Will any Cisco USB console driver work? I found one listed under a different model switch (https://software.cisco.com/download/home/284455380/type/282855122/release/3.1), but there doesn't appear to be any for the C1300/C1200 series (https://software.cisco.com/download/home/286331157/type).
That was one of the things I wanted to try, but could not find one amongst our spare cables before going out on vacation for a week. Now that I'm back, and seeing your post, I decided to give finding another one a go today and happened upon someone with one for charging their phone, so I borrowed that. This one works as expected! I can freely connect and disconnect it at any time and the COM port returns without the need to reboot the switch.
Best method I could find to do this was some instructions for Win 10 that posts say still work for Win 11 (https://www.tenforums.com/tutorials/73187-turn-off-usb-selective-suspend-windows-10-a.html#option2), but no affect on the C-to-C cable method.

I have tried a couple different USB C-to-C cables just to be sure it wasn't a faulty cable; all show the same issue.

Thoughts here? Is this likely a driver issue? I have tried both of the C ports on the laptop (which I think are technically Thunderbolt 4?), as well as the ports provided on the Dell WD22TB4 dock when it is plugged into the laptop.