A network engineer must adjust the STP interface attributes to influence root port selection.
Which two elements are used to accomplish this? (Choose two.)
Correct Answer: A,B
Explanation/Reference:
Explanation:
Spanning tree forces redundant data paths into a standby (blocked) state. If a network segment in the
spanning tree fails and a redundant path exists, the spanning-tree algorithm recalculates the spanning-tree
topology and activates the standby path. Switches send and receive spanning-tree frames, called bridge
protocol data units (BPDUs), at regular intervals. The switches do not forward these frames but use them
to construct a loop-free path. BPDUs contain information about the sending switch and its ports, including
switch and MAC addresses, switch priority, port priority, and path cost. Spanning tree uses this information
to elect the root switch and root port for the switched network and the root port and designated port for
each switched segment.
When two ports on a switch are part of a loop, the spanning-tree port priority and path cost settings control
which port is put in the forwarding state and which is put in the blocking state. The spanning-tree port
priority value represents the location of a port in the network topology and how well it is located to pass
traffic. The path cost value represents the media speed.
Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-
2_55_se/configuration/guide/3750xscg/swstp.html