UMN:CLI
User Manual
V8102
366
9.4.1.4
Port Priority
If the path-costs of two paths are same, decisions are based on port-priorities. In the fig-
ure below, suppose that two switches are connected. Since the path-costs of two paths
are both 100, their port priorities are compared and the port with smaller port priority is
selected to transmit the packet.
All these functions are automatically performed by BPDU, which is the bridge information
exchange between switches to activate or disable a specific port. It is also possible to
configure BPDU to modify the root switch or the path manually.
Fig. 9.22
Port Priority
Port States
Each port on a switch can be in one of five states.
Blocking
Listening
Learning
Forwarding
BPDUs or timeout indicate
Potential to become active
BPDUs indicate port
should not be active
Forwarding timer
expired
BPDUs indicate port
should not be active
BPDUs indicate port
should not be active
Forwarding timer
expired
Disabled
Fig. 9.23
Port States
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