During the listening state, the bridge performs these three steps:
1. Selects the root bridge
2. Selects the root ports on the nonroot bridges
3. Selects the designated ports on each segment
Link Comes Up
Blocking
(Moves to Listening
After It Decides
It Is a Root
Port or a
Designated Port)
Blocking
(Loss of BPDU Detected)
(Max Age = 20 Sec)
Listening
(Forward Delay = 15 Sec)
Learning
(Forward Delay = 15 Sec)
Forwarding
Improving Performance with Spanning Tree 53
The time that it takes for a port to transition from the listening state to the learning state or
from the learning state to the forwarding state is called the forward delay. The forward
delay has a default value of 15 seconds.
The learning state reduces the amount of ?¬‚ooding required when data forwarding begins.
If a port is still a designated or root port at the end of the learning state, the port transitions
to the forwarding state. In the forwarding state, a port is capable of sending and receiving
user data. Ports that are not the designated or root ports transition back to the blocking state.
A port normally transitions from the blocking state to the forwarding state in 30 to 50
seconds.
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