3Com Switch 4800G 24-Port Configuration Manual page 907

How a Cluster Works
Figure 268 Role change in a cluster
Candidate device
Designates
as a
management
device
Cancels the
designated
management
device
Management device
A device in a cluster changes its role according to the following rules:
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 configuration.
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.
Switch Clusteringv2 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 and maintenance of a cluster. Topology information collection and
cluster maintenance are independent from each other, with the former starting
before the cluster is created:
All devices use NDP to collect the information of the directly connected
■
neighbors, including their software version, host name, MAC address and port
number.
The management device uses NTDP to collect the information of the devices
■
within user-specified hops and the topology information of all devices and
specify the candidate devices of the cluster.
The management device adds or deletes a member device and modifies cluster
■
management configuration according to the candidate device information
collected through NTDP.
Cluster Management Overview
Leaves a
cluster
Joins a
cluster
Member device
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