2.5.2 - Force10 Networks

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}
154 Spanning Tree