1-5packet data. The receiving devices store the information carried in the NDP packet into the NDPtable but do not forward the NDP packet. When they receive another NDP packet, if the informationcarried in the packet is different from the stored one, the corresponding entry in the NDP table isupdated, otherwise only the holdtime of the entry is updated.Introduction to NTDPNTDP is a protocol used to collect network topology information. NTDP provides information requiredfor cluster management: it collects topology information about the switches within the specified hopcount, so as to provide the information of which devices can be added to a cluster.Based on the neighbor information stored in the neighbor table maintained by NDP, NTDP on themanagement device advertises NTDP topology collection requests to collect the NDP information ofeach device in a specific network range as well as the connection information of all its neighbors. Theinformation collected will be used by the management device or the network management software toimplement required functions.When a member device detects a change on its neighbors through its NDP table, it informs themanagement device through handshake packets, and the management device triggers its NTDP toperform specific topology collection, so that its NTDP can discover topology changes timely.The management device collects the topology information periodically. You can also launch anoperation of topology information collection by executing related commands. The process of topologyinformation collection is as follows.z The management device sends NTDP topology collection requests periodically through itsNTDP-enabled ports.z Upon receiving an NTDP topology collection request, the device returns a NTDP topologycollection response to the management device and forwards the request to its neighbor devicesthrough its NTDP-enable ports. The topology collection response packet contains the informationabout the local device and the NDP information about all the neighbor devices.z The neighbor devices perform the same operation until the NTDP topology collection request ispropagated to all the devices within the specified hops.When an NTDP topology collection request is propagated in the network, it is received and forwardedby large numbers of network devices, which may cause network congestion and the managementdevice busy processing of the NTDP topology collection responses. To avoid such cases, the followingmethods can be used to control the NTDP topology collection request advertisement speed.z Configuring the devices not to forward the NTDP topology collection request immediately after theyreceive an NTDP topology collection request. That is, configure the devices to wait for a periodbefore they forward the NTDP topology collection request.z Configuring each NTDP-enabled port on a device to forward an NTDP topology collection requestafter a specific period since the previous port on the device forwards the NTDP topology collectionrequest.
