STGs

The BayStack 470 supports a maximum of 8 multiple STGs, either all in one standalone switch or across a stack.When working with STGs, observe the following rules:

Enable load balancing using multiple STGs by configuring each path with a different VLAN and then assigning each VLAN to a separate STG.
Each STG must be independently configured.
With a maximum of 8 STGs, on average, each STG will have 32 VLANs.
In the default configuration of the BayStack 470, a single STG with the ID of 1 includes all ports on the switch.

The Default STG sends only untagged BPDUs in order to operate with all devices that support only one instance of STP.

Although ports can be added to or deleted from the Default STG, the Default STG itself cannot be deleted from the system.

All other STGs must be created by the user.
An STG cannot be deleted until you disable it. Additionally, you cannot delete an STG while it contains VLAN members, so you must first delete the VLANs from the STG.
The ports associated with a VLAN and VLANs themselves must be contained within a single STG.
When a VLAN spans multiple switches, the VLAN must be within the same spanning tree group (have the STG ID) across all the switches.
When a VLAN is assigned to an STG, all ports belonging to that VLAN automatically join the STG. And, all VLANs in the same shared database (SVL) must be assigned to the same STG.
All members of a particular MultiLink Trunking (MLT) group must be assigned to the same STG.
Tagged ports can belong to more than one STG, but untagged ports can belong to only one STG.

When a tagged port belongs to more than one STG, the egress BPDUs are tagged to distinguish the BPDUs of one STG from those of another STG. BPDUs from STG 1 (the Default STG) are untagged.

Because some STP-compliant devices do not support tagging, you can configure whether to send tagged or untagged BPDUs, even from tagged ports, with the BayStack 470 with software version 1.2. The VLAN ID for the tagged BPDUs will be 4000+STG ID.

Note: You cannot remove VLAN 1 from spanning tree group (STG) 1.

See also