The output of show spanning-tree summary command below shows that spanning tree is running in pvst mode on SW1. The first step in spanning tree convergence involves electing the root switch.
An STP topology with three switches has one link between each pair of switches. Which answer best describes the primary decision point as to which non-root switch has a designated port on the link between switches, and which does not? A) The device with the lowest BID would always become designated, and the other switch would block.
Three spanning tree modes can be configured on Cisco switches as shown in the output below. SW1 (config)#spanning-tree mode ? By default, Cisco Catalyst 3550 switches used to build this scenario have spanning tree enabled in pvst mode. PVST stands for Per-VLAN Spanning Tree Protocol and this mode runs an instance of IEEE 802.1d STP for each VLAN.
Spanning Tree Protocol (STP) ensures a loop-free topology in a local area network (LAN) made up of switches. It is desirable to have redundant links in a switched LAN so that a single link failure cannot interrupt normal operation of the network. But redundant links may also introduce physical switching loops that are undesirable.
Additionally, an edge port with RSTP connects to a single non-switch device, meaning it will be the designated port, and therefore reach a forwarding state. As for the incorrect answers, the RSTP backup and alternate port roles exist for a port to take over for some other designated port or root port, respectively.
Because SW4's fa0/1 is its root port, SW4 will not forward Hellos out that port, and because it is already a root port, SW4's fa0/1 cannot become a designated port.Only the root creates Hellos when the network is stable, so SW2 would never create Hellos.