How A Cluster Works - 3Com 4210G Series Configuration Manual

Figure 26-1 Network diagram for a cluster
As shown in Figure
management function is the management device, the other managed devices are member devices,
and the device that does not belong to any cluster but can be added to a cluster is a candidate device.
The management device and the member devices form the cluster.
Figure 26-2 Role change in a cluster
As shown in Figure
A candidate device becomes a management device when you create a cluster on it. A
management device becomes a candidate device only after the cluster is removed.
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.

How a Cluster Works

Cluster management is implemented through HW Group Management Protocol version 2 (HGMPv2),
which 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.
26-1, the device configured with a public IP address and performs the
26-2, a device in a cluster changes its role according to the following rules:
26-2