Operation Manual – Stack-ClusterH3C S3100 Series Ethernet Switches Chapter 2 Cluster2-42.1.3 How a Cluster WorksHGMPv2 consists of the following three protocols:z Neighbor discovery protocol (NDP)z Neighbor topology discovery protocol (NTDP)z ClusterA cluster configures and manages the devices in it through the above three protocols.Cluster management involves topology information collection and theestablishment/maintenance of a cluster. Topology information collection and clusterestablishment/maintenance are independent from each other. The former, as describedbelow, starts before a cluster is established.z All devices use NDP to collect the information about their neighbors, includingsoftware version, host name, MAC address, and port name.z The management device uses NTDP to collect the information about the deviceswithin specific hops and the topology information about the devices. It alsodetermines the candidate devices according to the information collected.z The management device adds the candidate devices to the cluster or removesmember devices from the cluster according to the candidate device informationcollected through NTDP.I. Introduction to NDPNDP is a protocol used to discover adjacent devices and provide information aboutthem. NDP operates on the data link layer, and therefore it supports different networklayer protocols.NDP is able to discover directly connected neighbors and provide the followingneighbor information: device type, software/hardware version, and connecting port. Inaddition, it may provide the following neighbor information: device ID, port full/halfduplex mode, product version, the Boot ROM version and so on.z An NDP-enabled device maintains an NDP neighbor table. Each entry in the NDPtable can automatically ages out. You can also clear the current NDP informationmanually to have neighbor information collected again.z An NDP-enabled device regularly broadcasts NDP packet through all its activeports. An NDP packet carries a holdtime field, which indicates how long thereceiving devices will keep the NDP packet data. The receiving devices store theinformation carried in the NDP packet into the NDP table but do not forward theNDP packet. When they receive another NDP packet, if the information carried inthe packet is different from the stored one, the corresponding entry in the NDPtable is updated, otherwise only the holdtime of the entry is updated.
