H3C S3100V2-52TP Configuration Manual page 179

Specifies the candidate switches of the cluster based on the collected information.
• The management switch adds or deletes a member switch and modifies cluster management
configuration according to the candidate switch information collected through NTDP.
Introduction to NDP
NDP is used to discover the 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
NDP information (including the switch name, software version, and connecting port, etc.) and the
holdtime, which is 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 in 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 an entry's holdtime expires (in other words, no NDP information from the neighbor is
received to restart the hold time before it ages out), the entry is removed from the NDP table.
NDP runs on the data link layer, and therefore supports different network layer protocols.
Introduction to 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
•
NTDP-enabled ports.
Upon receiving the request, the switch sends NTDP topology-collection response to the
•
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
•
to all the switches within specified hops.
When the NTDP topology-collection request is advertised in the network, large numbers of network
switches receive the NTDP topology-collection request and send NTDP topology-collection response at
the same time. This can cause congestion and may be a problem to the management switch. You can
configure the following delays to control the speed of the NTDP topology collection request
advertisement:
Instead of immediately forwarding an NTDP topology collection request when it is received, each
•
switch waits for a period of time. At the end of the specified delay, it forwards the NTDP topology
167