Spanning Tree Protocol
ExtremeWare XOS 11.3 Concepts Guide
424
The key points to remember when configuring VLANs and STP are:
â—Ź Each VLAN forms an independent broadcast domain.
â—Ź STP blocks paths to create a loop-free environment.
â—Ź 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 447.
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:
â—Ź Carrier
â—Ź 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 425 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.
The StpdID must be identical to the VLANid of the carrier VLAN in that STPD. See the section
“Specifying the Carrier VLAN” on page 424, for an example.
Protected VLAN
Protected VLANs are all other VLANs that are members of the STPD. These VLANs “piggyback” on the
carrier VLAN. Protected VLANs do not transmit or receive STP BPDUs, but they are affected by STP
state changes and inherit the state of the carrier VLAN. Protected VLANs can participate in multiple
STPDs, but any particular port in the VLAN can belong to only one STPD. Also known as non-carrier
VLANs.
Specifying the Carrier VLAN
The following example:
â—Ź Creates and enables an STPD named s8.
â—Ź Creates a carrier VLAN named v5.
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