Port Priority

What is port priority in STP ?

STP is a protocol to avoid loop in network, it has a standard method to overcome looping problem like Bridge ID, If a loop occurs in a network topology, and there is tie in bridge id , spanning tree can use the port priority value for the ports to decide which port has to be in forwarding state. The port priority is only used to determine the topology if the loop in the network cannot be resolved using bridge IDs or path cost.

STP uses to put port in forwarding first If a higher priority (lower numerical value) is assigned to a port. When a lower priority (higher numerical value) is assigned to a port, STP uses to put port in forwarding at last. If all ports have the same priority values, STP puts the lowest numbered interface in forwarding state and blocks all other interfaces.

Valid interfaces include physical interfaces and logical interfaces (port-channel, port-channel-number). Acceptable priority values range from 0 to 240, in increments of 16. The default is 128. Valid priority values are 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, and 240. All other values are rejected. The lower the the number, the higher the priority