3Com 4200G 12-Port Configuration Manual page 281

Introduction to NDP
Introduction to NTDP
Figure 84 Role changing rule
Candidate device Candidate device
Management device Management device
Each cluster has one (and only one) management device. A management device
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collects NDP/NTDP information to discover and determine candidate devices,
which can be then added into the cluster through manual configurations.
A candidate device becomes a member device after being added to a cluster.
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A member device becomes a candidate device after being removed from the
■
cluster.
NDP is the protocol for discovering the information about the adjacent nodes. NDP
operates on the data link layer, so it supports different network layer protocols.
NDP is used to discover the information about directly connected neighbors, including
the device type, software/hardware version, and connecting port of the adjacent
devices. It can also provide the information concerning device ID, port address,
hardware platform and so on.
A device with NDP enabled maintains an NDP information table. Each entry in an NDP
table ages with time. You can also clear the current NDP information manually to
have adjacent information collected again.
A device with NDP enabled broadcasts NDP packets regularly through all its ports that
are in up state. An NDP packet carries the holdtime, which indicates the period for the
receiving devices to keep the information the packet carries. Receiving devices only
store the information carried in the received NDP packets rather than forward them.
The corresponding data entry in the NDP table is updated when the information
carried in a received NDP packet if the received information differs from the existing
one, otherwise, only the holdtime of the corresponding entry is updated.
NTDP is a protocol for network topology information collection. NTDP provides the
information about the devices that can be added to clusters and collects the topology
information within the specified hops for cluster management.
Based on the NDP information table created by NDP, NTDP transmits and forwards
NTDP topology collection request to collect the NDP information and neighboring
connection information of each device in a specific network range for the
management device or the network administrator to implement needed functions.
Cluster Overview 267
Member device Member device