Quick Reference Guide

146 | Spanning Tree
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Spanning Tree Protocol (STP, IEEE 802.1D)
When SFTOS is set to run in basic Spanning Tree Protocol (STP) mode, SFTOS conforms to IEEE 802.1D
and the RFC 1493 Bridge MIB. A spanning tree algorithm provides path redundancy while preventing
undesirable loops in a network:
• SFTOS switching can be configured to run with STP enabled or disabled.
• Without STP, a path failure causes a loss of connectivity.
• STP allows only one active path at a time between any two network devices, but allows for backup
paths.
• When a topology change occurs, accelerated aging is used on the forwarding database(s).
STP allows port costs to be configured as zero, which causes the port to use IEEE 802.1D-recommended
values. In addition, per-port Administrative Mode affects sequence when the link comes up:
• Fast mode—listening and learning timers set to two seconds (this is recommended to avoid time-outs
during reconfiguration).
• Off/manual mode—port is always in forwarding mode (this is recommended, but only when no loops
are possible).
Basic STP (802.1D) CLI Management
Privileged and User Exec Mode CLI commands:
• Display STP settings and parameters for the switch:
— show spanning-tree summary
• Display STP settings and parameters for the bridge instance:
—
show spanning-tree [brief]
Global Config Mode CLI commands:
• [Disable] enable spanning tree for the switch:
— [no] spanning-tree
• Set maximum time for discarding STP configuration messages, default 20 seconds:
— [no] spanning-tree max-age 6-40
• Set time between STP config messages, default 2 seconds:
— [no] spanning-tree hello-time 1-10
• Set time spent in listening and learning, default 15 seconds:
— [no] spanning-tree forward-time 4-30
• Set MSTP Max Hops parameter for the common and internal spanning tree:
—
spanning-tree max-hops 1-127 (default is 20)
• Set Bridge Max Age parameter for the common and internal spanning tree:
—
spanning-tree max-age 6-40 (default is 20)
• Set the protocol Version parameter to a new value:
—
spanning-tree forceversion {802.1d | 802.1w | 802.1s}