Port disabled but not disabled

[AnotherRon]

I have two MS120-24P switches equipped with 1000BASE-SX: 1.3 Gbps SFP modules on port 28, and connected to each other with MM fibre. The second switch (call it MS02) was issuing UDLD alerts on the port, but there was no UDLD alerts on port 28 of MS01, which I find strange. If one end of the connection is unidirectional it must surely be the same on the other end?

There is another trunk between the two switches so I disabled port 28 on MS01, but port 28 on MS02, the partner port stays active. Why? Does disabled not mean disabled?

Also, while the MS01 port was disabled, the SFP module was reseated, and I see this activity on the event log of MS02 in the form of RSTP role changes.

Can anyone clarify what disabling a port actually does? My understanding is that is should be the equivalent of an admin shutdown on a Cisco switch, but the logs and port status indicate that this isn't the case.

[KH]

Hey @AnotherRon 

You are correct, disabling the port should be similar to an admin shutdown. I would ensure however that the config was pushed to the switch. UDLD errors usually may coincide with loops/general connectivity issues so its possible that its having a hard time fetching config. You can check that it says up to date in the bottom left corner. The port should look like this:

[AnotherRon]

Thanks for the response. Here is the port status on the B side of the connection where the port is configured as enabled:

Here is the status of the A side if the connection where the port is disabled:

As you can see, the B end has an active status despite the A end being disabled.

[AnotherRon]

The only plausible explanation that I can think of is that there is a repeater/bridge in the fibre that maintains link layer connectivity on the B end, but the cabling contractor insists that it's pure end to end fibre. Unfortunately I'm in London and the kit is in Nice so I'm not in a position to verify.

[KH]

That would be one of the only things that makes sense. You could also take a Packet capture on that port which might give you an idea of what's on the other end.

[cmr]

What about the new transceiver receive and transmit power monitoring, couldn't that help here?

[AnotherRon]

The packet counter on the interface aren't incrementing so there's nothing happening on the port. A packet capture is empty.  It's behaving in the same way a port would if connected to a media converter with link fault pass through set to off. That is, active connection to the media converter, but no connection beyond .