Specifications

Spanning Tree Domains
ExtremeWare XOS 11.0 Concepts Guide 197
Spanning Tree Domains
The switch can be partitioned into multiple virtual bridges. Each virtual bridge can run an independent
Spanning Tree instance. Each Spanning Tree instance is called a Spanning Tree Domain (STPD). Each
STPD has its own root bridge and active path. After an STPD is created, one or more VLANs can be
assigned to it.
A physical port can belong to multiple STPDs. In addition, a VLAN can span multiple STPDs.
The key points to remember when configuring VLANs and STP are:
• Each VLAN forms an independent broadcast domain.
• STP blocks paths to create a loop-free environment.
• Within any given STPD, all VLANs belonging to it use the same spanning tree.
To create an STPD, use the following command:
create stpd <stpd_name>
To delete an STPD, use the following command:
delete stpd <stpd_name>
For more detailed information about configuring STP and STP parameters, see “Configuring STP on the
Switch” on page 220.
Member VLANs
When you add a VLAN to an STPD, that VLAN becomes a member of the STPD. The two types of
member VLANs in an STPD are:
• Carrier
• Protected
Carrier VLAN
A carrier VLAN defines the scope of the STPD, which includes the physical and logical ports that
belong to the STPD and the 802.1Q tag used to transport EMISTP or PVST+ encapsulated BPDUs (see
“Encapsulation Modes” on page 199 for more information about encapsulating STP BPDUs). Only one
carrier VLAN can exist in a given STPD, although some of its ports can be outside the control of any
STPD at the same time.
STPD mode The mode of operation for the STPD. The two modes of operation are:
• 802.1D—Compatible with legacy STP and other devices using the IEEE 802.1D
standard
• 802.1W—Compatible with Rapid Spanning Tree (RSTP)
For more information about how to configure STPD modes, see “STPD Modes” on
page 198.
Table 36: STP terms (continued)
Term Description