Extreme Networks ExtremeWare Command Reference Manual page 702

STP Commands
All STP parameters default to the IEEE 802.1D values, as appropriate.
Port Modes
An STP port has three modes of operation:
• 802.1D mode
This mode is used for backward compatibility with previous STP versions and for compatibility with
third-party switches using IEEE standard 802.1D. BPDUs are sent untagged in 1D mode. Because of
this, on any given physical interface there can be only one STPD running in 1D mode.
• Extreme Multiple Instance Spanning Tree Protocol (EMISTP) mode
EMISTP mode is an extension of STP that allows a physical port to belong to multiple STPDs by
assigning the port to multiple VLANs. EMISTP adds significant flexibility to STP network design.
BPDUs are sent with an 802.1Q tag having an STPD instance Identifier (StpdID) in the VLANid field.
• PVST+ mode
This mode implements PVST+ in compatibility with third-party switches running this version of
STP. The STPDs running in this mode have a one-to-one relationship with VLANs, and send and
process packets in PVST+ format.
These port modes are for STP ports, not for physical ports. When a physical port belongs to multiple
STPDs, it is associated with multiple STP ports It is possible for the physical port to run in different
modes for different domains to which it belongs.
702 ExtremeWare Software 7.0.0 Command Reference Guide