https://kb.vmware.com/s/article/2047822
Bridged Protocol Data Units (BPDUs) are the frames that are exchanged between physical switches as part of the Spanning Tree Protocol (STP). STP is used to prevent loops in the network and is commonly enabled on physical switches. When a link on a physical switch port goes up, the STP protocol starts its calculation and BPDU exchange to determine if the port should be in forwarding or blocking state. Bridge Protocol Data Unit (BPDU) frames exchange across the physical switch ports to identify the Root Bridge and form a tree topology. VMware’s vSwitches do not support STP and do not participate in BPDU exchanges. If a BPDU frame is received on a vSwitch uplink, that frame is not processed for STP and traverses the vSwitch. For best practice, either the physical switch should have BPDU filters enabled or the Net.BlockGuestBPDU option on the host should be enabled in order for those BPDU frames to be blocked. The BPDU filter needs to be enabled on the physical switch or host to prevent physical ports to go down. Likewise, VMware vSwitches do not generate BPDU frames.
Note: VMware vSwitches (Standard and Distributed) cannot form loops as there is no way to join two virtual switches together at layer 2 of the OSI layer. As such, no Spanning Tree Protocol functionality has been incorporated into the virtual switches.
The STP process of identifying root bridge and finding if the switch ports are in forwarding or blocking state takes somewhere around 30 to 50 seconds. During that time no data can be passed from those switch ports. If a server connected to the port cannot communicate for that long, the applications running on them will time out. To avoid this issue of time out on the servers, the best practice is to enable Port Fast configuration on the switch ports where the server’s NICs are connected. The Port Fast configuration puts the physical switch port immediately into STP forwarding state. For more information, see STP may cause temporary loss of network connectivity when a failover or failback event occurs (1003804).
