How A Cluster Works - 3Com 4200G 12-Port Configuration Manual

Figure 2-2 State machine of cluster role
A candidate device becomes a management device when you create a cluster 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.
A member device becomes a candidate device after it is removed from the cluster.
A management device becomes a candidate device only after the cluster is removed.
After you create a cluster on an Switch 4200G switch, 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.

How a Cluster Works

HGMPv2 consists of the following three protocols:
Neighbor discovery protocol (NDP)
Neighbor topology discovery protocol (NTDP)
Cluster
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.
All devices use NDP to collect the information about their neighbors, including software version,
host name, MAC address, and port name.
The management device uses NTDP to collect the information about the devices within specific
hops and the topology information about the devices. It also determines the candidate devices
according to the information collected.
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