Not necessary.
Not necessary.
Looking into this setup, I'm wondering if a nasty loop might have formed. Virtual switches function like regular switches, and having them across three hosts raises the question of whether STP is necessary. My environment is typical—multi-node vSphere cluster with various VLAN port groups. It's impressive how well networking is handled here. I manage a USG supporting three VLANs: v120 for management, v21 for WiFi, and v130 for internet traffic directed to pfSense. Behind pfSense are additional VLANs: v20, v30, v50, and v240. A basic layout would show Internet at the top, followed by Unifi Secure Gateway, then port 1 ESXiHOST#3 running a VM-pfSense with hardware passthrough for WAN (v130). Port 2 connects to a Nexus 3048 Switch via trunked ports (v120, v21), and Port 3 links to an Unifi Access Point (v21). ESXi hosts 1-3 each have one 10GB and two 1GB connections per port to the switch, all using trunking (v20, v30, v50, v240). Everything operates on a distributed virtual switch with dedicated port groups for each VLAN. My physical setup includes a FreeNAS box with two 10GB links—one v240 for iSCSI and another v30 for SMB/management traffic.
VSwitch includes advanced forwarding settings to stop cycles without needing STP. A broadcast storm becomes obvious fast.