User guide

Spanning Tree Domains
ExtremeWare 7.2e Installation and User Guide 193
Port Modes
An STP port has two 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.
• 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. The Summit 400 restricts each physical port
to a single STPD.
STPD Identifier
An StpdID is used to identify each STP domain. You assign the StpdID when configuring the domain,
and that VLAN cannot belong to another STPD.
An StpdID must be identical to the VLANid of one of the member VLANs in that STP domain.
NOTE
If an STPD contains at least one port not in 1D mode, the STPD must be configured with an StpdID.
STPD BPDU Tunneling
You can configure ExtremeWare to allow a BDPU to traverse a VLAN without being processed by STP,
even if STP is enabled on the port. This is known as BPDU tunneling.
To enable and disable BPDU tunneling on a VLAN, use one of the following commands:
enable ignore-bpdu vlan <vlan name>
disable ignore-bpdu vlan <vlan name>
If you have a known topology and have switches outside of your network within your STPD, use this
feature to keep the root bridge within your network.
Rapid Root Failover
ExtremeWare supports rapid root failover for faster STP failover recovery times in STP 802.1d mode. If
the active root port link goes down ExtremeWare recalculates STP and elects a new root port. Rapid root
failover allows the new root port to immediately begin forwarding, skipping the standard listening and
learning phases. Rapid root failover occurs only when the link goes down, and not when there is any
other root port failure, such as missing BPDUs.
The default setting is disabled. To enable rapid root failover, use the following command:
enable stpd <spanning tree name> rapid-root-failover