146 | Spanning Treew w w . d e l l . c o m | s u p p o r t . d e l l . c o mSpanning Tree Protocol (STP, IEEE 802.1D)When SFTOS is set to run in basic Spanning Tree Protocol (STP) mode, SFTOS conforms to IEEE 802.1Dand the RFC 1493 Bridge MIB. A spanning tree algorithm provides path redundancy while preventingundesirable 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 backuppaths.• 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-recommendedvalues. 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-outsduring reconfiguration).• Off/manual mode—port is always in forwarding mode (this is recommended, but only when no loopsare possible).Basic STP (802.1D) CLI ManagementPrivileged 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}
