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5 - Hello Time
The Hello Time option specifies the interval between the transmission of protocol configuration information by a
bridge that is, or is attempting to become, the Root. In the Spanning Tree Protocol, only one bridge can be the Root
Bridge. The Root Bridge generates a Configuration message after an interval set by this timer. (The Root is saying,
"Hello, I'm still here".) All other bridges in the network wait for this Configuration message within the Network
Hello Time to confirm that the topology is stable. If any bridge does not receive the Configuration message within
the expected time, it will send out Topology Change messages to the other bridges in order to calculate a new
configuration.
Default:
[2 sec] (IEEE 802.1D recommendation)
Range:
1 to 10 seconds
Considerations:
This value is not directly used in configuration calculations but the bridged network uses the value set at the
Root Bridge. (I.e. Network Hello Time).
Lower Value
Reducing this value increases the frequency of Configuration messages on the network, potentially creating
excessive network traffic.
Higher Value
A higher value results in a slower response to a change in the topology of the network (e.g.
addition/deletion/failure of bridges or communications paths).
Recommendations:
The default value of 2 seconds is recommended by the IEEE 802.1D standard as a reasonable balance of
performance. If a change is deemed necessary, increasing the value in small steps is the recommended action.
The following relationship to Max Age must be maintained:
Max Age > 2 x (Hello Time + 1.0)
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