Technical data

BLADE OS 5.1 Application Guide
76
 Chapter 5: Spanning Tree Group BMD00136, November 2009
Spanning Tree Group Guidelines
This section provides important information on configuring Spanning Tree Groups (STGs):
Adding a VLAN to a Spanning Tree Group
 If no VLANs exist beyond the default VLAN 1 see “Creating a VLAN” on page 76 for
information on adding ports to VLANs.
 Add the VLAN to the STG using the following command:
Note – To ensure proper operation with switches that use Cisco Per VLAN Spanning
Tree (PVST+), you must either create a separate STG for each VLAN, or manually add all
associated VLANs into a single STG.
Creating a VLAN
When you create a VLAN, that VLAN automatically belongs to STG 1, the default STG. If you
want the VLAN in another STG, you must move the VLAN by assigning it to another STG.
 Move a newly created VLAN to an existing STG by following this order:
 Create the VLAN
 Add the VLAN to an existing STG
 VLANs must be contained within a single STG; a VLAN cannot span multiple STGs. By
confining VLANs within a single STG, you avoid problems with spanning tree blocking ports
and causing a loss of connectivity within the VLAN. When a VLAN spans multiple switches, it
is recommended that the VLAN remain within the same Spanning Tree Group (have the same
STG ID) across all the switches.
 If ports are tagged, all trunked ports can belong to multiple STGs.
 A port that is not a member of any VLAN cannot be added to any STG. The port must be added
to a VLAN, and that VLAN added to the desired STG.
>> # spanning-tree stp <STG number> vlan <VLAN number>