In my case, the ports go down and couple seconds after they go up, then the ports go into STP forwarding status. There is nothing else on the logs prior to the ports going down. I am working remotely so I don't know if the recommended cable lengths was exceeded.
These is what I have tried so far:
Update firmware to the latest version.
Turned off PorFast.
Enabled BPDU-Guard on all the access interfaces.
Disabled Energy Enhanced Ethernet.
Disabled trunk negotiation
Hard coded the interfaces as Full Duplex and Speed 1000.
Can you believe we are still having this issue with this switch? I just discovered that the same thing is happening to multiple of our SG300 switches. I have called Cisco and they have NO IDEA of what is going on. I believe this is a firmware issue because I've found other people on the web having the same problem. We have updated the firmware to the latest version and still nothing. The cable lengths are ok. I actually have a printer and a UPS NICs connected to the switch with 5 feet cables and both of those ports are flapping just like the other ones. I disabled STP globally on this switch but the problem continued. I configured MSTP on the whole network and the problem continues. It is hard for me to believe that there is something in the network causing this issue because the interfaces flap randomly at different times.
Any help with this from anybody will be greatly appreciated.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...