Specifications

136 ExtremeWare XOS 10.1 Concepts Guide
Spanning Tree Protocol (STP)
STP Terms
Table 27 describes the terms associated with STP.
Table 27: STP terms
Term Description
autobind If enabled, autobind automatically adds or removes ports from the STPD. If ports are
added to the carrier VLAN, the member ports of the VLAN are automatically added
to the STPD. If ports are removed from the carrier VLAN, those ports are also
removed from the STPD. For more information about the autobind feature and
adding ports to an STPD, see “Binding Ports” on page 140.
carrier VLAN Carrier VLANs define the scope of the Spanning Tree Domain (STPD) including the
physical and logical ports that belong to the STPD and the 802.1q tag used to
transport EMISTP or PVST+ encapsulated BPDUs. Only one carrier VLAN can exist
in any given STP domain. For more information about carrier VLANs, see “Member
VLANs” on page 137.
default encapsulation mode Default encapsulation allows you to specify the type of BPDU encapsulation to use
for all ports added to a given STPD, not just one individual port. There are three
encapsulation modes:
• 802.1d—This mode is used for backward compatibility with previous STP versions
and for compatibility with third-party switches using IEEE standard 802.1d.
• EMISTP—Extreme Multiple Instance Spanning Tree Protocol (EMISTP) mode is
an extension of STP that allows a physical port to belong to multiple STPDs by
assigning the port to multiple VLANs.
• PVST+ —This mode implements PVST+ in compatibility with third-party switches
running this version of STP.
For more information about how to configure the default encapsulation mode, see
“Encapsulation Modes” on page 139.
encapsulation mode You can configure ports within an STPD to accept specific BPDU encapsulations.
There are three encapsulation modes:
• 802.1d—This mode is used for backward compatibility with previous STP versions
and for compatibility with third-party switches using IEEE standard 802.1d.
• EMISTP—Extreme Multiple Instance Spanning Tree Protocol (EMISTP) mode is
an extension of STP that allows a physical port to belong to multiple STPDs by
assigning the port to multiple VLANs.
• PVST+ —This mode implements PVST+ in compatibility with third-party switches
running this version of STP.
For more information about how to configure encapsulation modes, see
“Encapsulation Modes” on page 139.
protected VLAN Protected VLANs are the other VLANs that are members of the STPD but do not
define the scope of the STPD. 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. Also known as non-carrier VLANs. For more information about
protected VLANs, see “Member VLANs” on page 137.
Spanning Tree Domain An STP instance that contains one or more VLANs. The switch can run multiple
Spanning Tree Domains (STPDs). For more information about STPD, see “Spanning
Tree Domains” on page 137.
STPD mode The mode of operation for the STPD. There are two modes of operation:
• 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 138.