Dell PowerConnect FCS624S Configuration Guide - Page 307

Configuring STP related features 8 TABLE 54 CLI display of show spanning-tree 802.1W (Continued) This field... Displays... Machine States Received The current states of the various state machines on the port: • PIM - State of the Port Information state machine. • PRT - State of the Port Role Transition state machine. • PST - State of the Port State Transition state machine. • TCM - State of the Topology Change state machine. • PPM - State of the Port Protocol Migration. • PTX - State of the Port Transmit state machine. Refer to the section "State machines" on page 233 for details on state machines. Shows the number of BPDU types the port has received: • RST BPDU - BPDU in 802.1W format. • Config BPDU - Legacy configuration BPDU (802.1D format). • TCN BPDU - Legacy topology change BPDU (802.1D format). 802.1W Draft 3 As an alternative to full 802.1W, you can configure 802.1W Draft 3. 802.1W Draft 3 provides a subset of the RSTP capabilities described in the 802.1W STP specification. 802.1W Draft 3 support is disabled by default. When the feature is enabled, if a root port on a Dell PowerConnect device that is not the root bridge becomes unavailable, the device can automatically Switch over to an alternate root port, without reconvergence delays. 802.1W Draft 3 does not apply to the root bridge, since all the root bridge ports are always in the forwarding state. Figure 49 shows an example of an optimal STP topology. In this topology, all the non-root bridges have at least two paths to the root bridge (Switch 1 in this example). One of the paths is through the root port. The other path is a backup and is through the alternate port. While the root port is in the forwarding state, the alternate port is in the blocking state. PowerConnect B-Series FCX Configuration Guide 265 53-1002266-01