H3C Technologies H3C S5120 Series Switches - Manual (Page 674)

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cluster. Different from a member device, its topology information has been collected by the
management device but it has not been added to the cluster.
Figure 1-1 Network diagram for a cluster
As shown in Figure 1-1 , the device configured with a public IP address and performing the 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 1-2 Role change in a cluster
As shown in Figure 1-2 , a device in a cluster changes its role according to the following rules:
z 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.
z 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:
z Neighbor Discovery Protocol (NDP)
z Neighbor Topology Discovery Protocol (NTDP)
z 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:
z All devices use NDP to collect the information of the directly connected neighbors, including their
software version, host name, MAC address and port number.
z 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.
z The management device adds or deletes a member device and modifies cluster management