How A Cluster Works - HP 5820X Switch Configuration Manual

As shown in
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 60 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
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device only becomes a candidate device after the cluster is removed.
A candidate device becomes a member device after being added to a cluster. A member device
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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 protocols:
NDP
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NTDP
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Cluster
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A cluster configures and manages the devices in it through the 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; the following workflow applies:
• 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
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hops and the topology information of all devices, and then determines the candidate devices of the
cluster based on the collected information.
The management device adds or deletes a member device and modifies cluster management
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configuration according to the candidate device information collected through NTDP.
Introduction to NDP
NDP discovers the information about directly connected neighbors, including the device name, software
version, and connecting port of the adjacent devices. NDP works in the following ways:
A device running NDP periodically sends NDP packets to its neighbors. An NDP packet carries NDP
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information (including the device name, software version, and connecting port, and so on) and the
holdtime, which indicates how long the receiving devices will keep the NDP information. At the
same time, the device also receives (but does not forward) the NDP packets from its neighbors.
A device running NDP stores and maintains an NDP table. The device creates an entry in the NDP
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table for each neighbor. If a new neighbor is found, meaning that the device receives an NDP
packet sent by the neighbor for the first time, the device adds an entry in the NDP table. If the NDP
information carried in the NDP packet is different from the stored information, the corresponding
Figure 59, the device configured with a public IP address and performing the management
60, a device in a cluster changes its role according to the following rules:
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