Operation Manual – DLDPH3C S7500 Series Ethernet Switches Chapter 1 DLDP Configuration1-6Table 1-4 Processing procedure when no echo packet is received from the neighborNo echo packet received from theneighbor Processing procedureIn normal mode, no echo packet isreceived when the echo waiting timerexpires.In enhanced mode, no echo packet isreceived when the enhanced timerexpiresDLDP switches to the disable state,outputs log and tracking information, andsends flush packets. Depending on theuser-defined DLDP down mode, DLDPdisables the local port automatically orprompts you to disable the portmanually. DLDP sends RSY messagesand removes the correspondingneighbor entries.1.2.2 DLDP StatusA link can be in one of these DLDP states: initial, inactive, active, advertisement, probe,disable, and delaydown.Table 1-5 DLDP statusStatus DescriptionInitial Initial status before DLDP is enabled.Inactive DLDP is enabled but the corresponding link is downActive DLDP is enabled, and the link is up or an neighbor entry isclearedAdvertisementAll neighbors communicate normally in both directions, orDLDP remains in active state for more than five seconds andenters this status. It is a stable state where no unidirectional linkis foundProbeDHCP sends packets to check whether the link is aunidirectional. It enables the probe sending timer and an echowaiting timer for each target neighbor.DisableDLDP detects a unidirectional link, or finds (in enhanced mode)that a neighbor disappears. In this case, DLDP sends andreceives only recover probe packets and recover echo packets.DelayDownWhen a device in the active, advertisement, or probe DLDPstate receives a port down message, it does not removes thecorresponding neighbor immediately, neither does it changesto the inactive state. Instead, it changes to the delaydown statefirst.When a device changes to the delaydown state, the relatedDLDP neighbor information remains, and the DelayDown timeris triggered. After the DelayDown timer expires, the DLDPneighbor information is removed.
