How A Cluster Works - 3Com 4500 PWR 26-Port Configuration Manual

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.
After you create a cluster on a Switch 4500 switch, the switch collects the network topology information
periodically and adds the candidate switches it finds to the cluster. The interval for a management
device to collect network topology information is determined by the NTDP timer. If you do not want the
candidate switches to be added to a cluster automatically, you can set the topology collection interval to
0 by using the ntdp timer command. In this case, the switch does not collect network topology
information periodically.

How a Cluster Works

HGMPv2 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/maintenance of a
cluster. Topology information collection and cluster establishment/maintenance are independent from
each other. The former, as described below, starts before a cluster is established.
All devices use NDP to collect the information about their neighbors, including software version,
host name, MAC address, and port name.
The management device uses NTDP to collect the information about the devices within specific
hops and the topology information about the devices. It also determines the candidate devices
according to the information collected.
The management device adds the candidate devices to the cluster or removes member devices
from the cluster according to the candidate device information collected through NTDP.
Introduction to NDP
NDP is a protocol used to discover adjacent devices and provide information about them. NDP operates
on the data link layer, and therefore it supports different network layer protocols.
NDP is able to discover directly connected neighbors and provide the following neighbor information:
device type, software/hardware version, and connecting port. In addition, it may provide the following
neighbor information: device ID, port full/half duplex mode, product version, the Boot ROM version and
so on.
An NDP-enabled device maintains an NDP neighbor table. Each entry in the NDP table can
automatically ages out. You can also clear the current NDP information manually to have neighbor
information collected again.
An NDP-enabled device regularly broadcasts NDP packet through all its active ports. An NDP
packet carries a holdtime field, which indicates how long the receiving devices will keep the NDP
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