3Com 4210 PWR Configuration Manual page 322

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HAPTER LUSTER
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How a Cluster Works
Figure 100 State machine of cluster role
Management device
A candidate device becomes a management device when you create a cluster
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on it. Note that a cluster must have one (and only one) management device.
On becoming a management device, the device collects network topology
information and tries to discover and determine candidate devices, which can
then be added to the cluster through configurations.
A candidate device becomes a member device after being added to a cluster.
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A member device becomes a candidate device after it is removed from the
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cluster.
A management device becomes a candidate device only after the cluster is
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removed.
After you create a cluster on a Switch 4210, the switch collects the network
topology information periodically and adds the candidate switches it finds to the
cluster. The interval for a management device to collect network topology
information is determined by the NTDP timer. If you do not want the candidate
switches to be added to a cluster automatically, you can set the topology
collection interval to 0 by using the ntdp timer command. In this case, the switch
does not collect network topology information periodically.
Switch Clusteringv2 consists of the following three protocols:
Neighbor discovery protocol (NDP)
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Neighbor topology discovery protocol (NTDP)
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Cluster
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A cluster configures and manages the devices in it through the above three
protocols.
Cluster management involves topology information collection and the
establishment/maintenance of a cluster. Topology information collection and
cluster establishment/maintenance are independent from each other. The former,
as described below, starts before a cluster is established.
Candidate device
Member device