Specifications
198 ExtremeWare XOS 11.0 Concepts Guide
Spanning Tree Protocol
The StpdID must be identical to the VLANid of the carrier VLAN in that STPD. See the section
“Specifying the Carrier VLAN” on page 198, 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:
• Creates and enables an STPD named s8.
• Creates a carrier VLAN named v5.
• Assigns VLAN v5 to STPD s8.
• Creates the same tag ID for the VLAN and the STPD (the carrier VLAN’s VLANid must be identical
to the STPDs StpdID).
create vlan v5
configure vlan v5 tag 100
configure vlan v5 add ports 1:1-1:20 tagged
create stpd s8
configure stpd s8 add vlan v5 ports all emistp
configure stpd s8 tag 100
enable stpd s8
Notice how the tag number for the VLAN v5 and the STPD s8 is identical (the tag is 100). By using
identical tags, you have selected the carrier VLAN. The carrier VLAN’s VLANid is identical to the
STPD’s StpdID.
STPD Modes
An STPD has two modes of operation:
• 802.1D mode
Use this mode for backward compatibility with previous STP versions and for compatibility with
third-party switches using IEEE standard 802.1D. When configured in this mode, all rapid
configuration mechanisms are disabled.
• 802.1W mode
Use this mode for compatibility with Rapid Spanning Tree (RSTP). When configured in this mode,
all rapid configuration mechanisms are enabled. The benefit of this mode is available on
point-to-point links only and when the peer is likewise configured in 802.1W mode. If you do not
select point-to-point links and the peer is not configured for 802.1W mode, the STPD fails back to
802.1D mode.
You enable or disable RSTP on a per STPD basis only. You do not enable RSTP on a per port basis.
For more information about RSTP and RSTP features, see “Rapid Spanning Tree Protocol” on
page 209.