I upgraded many Dell 6248 switches to the latest and greatest firmware over the weekend. I have been experiencing more packet loss than I would ever want to see on an internal LAN. Connecting from the servers on the same switch would yield a periodic lost packet for no apparent reason. There were some clues on the switch with logged “spanning tree topology changes” in the log file. During this log event, I would drop packets not only on the local switch, but other connecting switches as well. All of these switches are configured with Rapid STP, LAG groups between them, and two VLANs.
Reading up on the dell site, I saw some good advice entailing turning on “Port Fast” on every port that isn’t an edge link between switches, namely ports connected to switches and servers. This advice appears to be valid. With the latest firmware I could go to Global STP settings and simply enable Port Fast. It was smart enough to not turn it on for the LAG groups and switch interconnects with multi-vlans on them. So far so good…over the past few hours I haven’t had any dropped packets.