Operation Manual – MulticastH3C S5500-EI Series Ethernet Switches Chapter 7 PIM Configuration7-17To do... Use the command... RemarksEnable PIM-DM pim dm RequiredDisabled by defaultCaution:z All the interfaces of the same router must work in the same PIM mode.z PIM-DM cannot be used for multicast groups in the SSM group grange.7.2.4 Enabling State RefreshAn interface without the state refresh capability cannot forward state refresh messages.Follow these steps to enable the state refresh capability:To do... Use the command... RemarksEnter system view system-view —Enter interface view interface interface-typeinterface-number —Enable state refresh pimstate-refresh-capableOptionalEnabled by default7.2.5 Configuring State Refresh ParametersTo avoid the resource-consuming reflooding of unwanted traffic caused by timeout ofpruned interfaces, the router directly connected with the multicast source periodicallysends an (S, G) state refresh message, which is forwarded hop by hop along the initialmulticast flooding path of the PIM-DM domain, to refresh the prune timer state of all therouters on the path.A router may receive multiple state refresh messages within a short time, of whichsome may be duplicated messages. To keep a router from receiving such duplicatedmessages, you can configure the time the router must wait before receiving the nextstate refresh message. If a new state refresh message is received within the waitingtime, the router will discard it; if this timer times out, the router will accept a new staterefresh message, refresh its own PIM state, and reset the waiting timer.The TTL value of a state refresh message decrements by 1 whenever it passes a routerbefore it is forwarded to the downstream node until the TTL value comes down to 0. Ina small network, a state refresh message may cycle in the network. To effectively
