HP 5500 EI Series Configuration Manual page 188

version, host name, MAC address and port number.
The management switch uses NTDP to collect data on the switches within user-specified hops and
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their topology data, and identifies candidate switches based on the topology data.
The management switch adds or deletes a member switch and modifies the cluster management
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configuration according to the candidate switch information collected through NTDP.
About NDP
NDP discovers information about directly connected neighbors, including the switch name, software
version, and connecting port of the adjacent switches. NDP works in the following ways:
A switch running NDP periodically sends NDP packets to its neighbors. An NDP packet carries
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NDP information (including the switch name, software version, and connecting port) and the
holdtime. The holdtime indicates how long the receiving switches will keep the NDP information. At
the same time, the switch also receives, but does not forward, NDP packets from its neighbors.
• A switch running NDP stores and maintains an NDP table. The switch creates an entry in the NDP
table for each neighbor. If a new neighbor is found, meaning the switch receives an NDP packet
sent by the neighbor for the first time, the switch 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 is received from the neighbor when the holdtime times out, the
corresponding entry is removed from the NDP table.
NDP runs on the data link layer and supports different network layer protocols.
About NTDP
NTDP provides information required for cluster management. It collects topology information about the
switches within the specified hop count. Based on the neighbor information stored in the neighbor table
maintained by NDP, NTDP on the management switch advertises NTDP topology-collection requests to
collect the NDP information of all the switches in a specific network range as well as the connection
information of all its neighbors. The information collected will be used by the management switch or the
network management software to implement required functions.
When a member switch detects a change on its neighbors through its NDP table, it informs the
management switch through handshake packets. Then the management switch triggers its NTDP to
collect specific topology information, so that its NTDP can discover topology changes promptly.
The management switch collects topology information periodically. You can also administratively launch
a topology information collection. The process of topology information collection is as follows:
The management switch periodically sends NTDP topology-collection request from the
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NTDP-enabled ports.
Upon receiving the request, the switch sends NTDP topology-collection response to the
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management switch, copies this response packet on the NTDP-enabled port, and sends it to the
adjacent switch. Topology-collection response includes the basic information of the NDP-enabled
switch and NDP information of all adjacent switches.
The adjacent switch performs the same operation until the NTDP topology-collection request is sent
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