R2511-HP MSR Router Series Network Management and Monitoring Configuration Guide(V5)

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As shown in Figure 24, the d
evice 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 25 Role change in a cluster
As shown in Figure 25, 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. A
management device becomes a candidate device only after the cluster is removed.
• A candidate device becomes a member device after it is 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 the HW Group Management Protocol version 2 (HGMPv2),
which comprises of the following three protocols:
• Neighbor Discovery Protocol (NDP)
• Neighbor Topology Discovery Protocol (NTDP)
• Cluster
These protocols enable topology data collection and cluster establishment and maintenance.
The following is the topology data collection procedure:
• Every device uses NDP to collect data on the directly connected neighbors, including their software
version, host name, MAC address and port number.
• The management device uses NTDP to collect data on the devices within user-specified hops and
their topology data, and identifies candidate devices based on the topology data.
• The management device adds or deletes a member device and modifies the cluster management
configuration according to the candidate device information collected through NTDP.
About NDP
NDP discovers 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 information (including the device name, software version, and connecting port) and the
holdtime. The holdtime 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
table for each neighbor. If a new neighbor is found, meaning the device receives an NDP packet
sent by the neighbor for the first time, the device adds an entry to the NDP table. If the NDP
information carried in the NDP packet is different from the stored information, the corresponding
entry and holdtime in the NDP table are updated. Otherwise, only the holdtime of the entry is
updated. If no NDP information from the neighbor is received when the holdtime times out, the
corresponding entry is removed from the NDP table.