Extreme Networks ExtremeWare 7.3.0, Command Reference Manual

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1004 ExtremeWare Software 7.3.0 Command Reference Guide
STP Commands
• STP blocks paths to create a loop-free environment.
• When STP blocks a path, no data can be transmitted or received on the blocked port.
• Within any given STPD, all VLANs belonging to it use the same spanning tree.
If you delete a STPD, the VLANs that were members of that STPD are also deleted. You must remove
all VLANs associated with the STP before deleting the STPD.
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. This mode is available for point-to-point links only.
RSTP is enabled or disabled on a per STPD basis only. You do not enable RSTP on a per port basis.
By default, the:
• STPD operates in 802.1d mode
• Default device configuration contains a single STPD called s0
• Default VLAN is a member of STPD s0
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.