User's Manual

Table Of Contents
519
Users Manual of CS-6306R
As long as source S still sends information to group G, the first-hop switch will periodically send the refreshing
information of the routing item (S,G) to the nether original broadcast tree to finish refreshing. The state
refreshing mechanism of PIM-DM can refresh the state of the downstream, ensuring that the pruning of the
broadcast tree does not time out.
In the multi-access network, besides the DR selection, PIM-DM also introduces the following mechanisms:
Use the assertion mechanism to select the unique forwarder to prevent the multicast packet from being
repeatedly forwarded.
Use the add/prune restraint mechanism to reduce redundant add/prune information.
Use the pruning deny mechanism to deny improper pruning actions.
In the PIM-DM domain, the switches that run PIM-DM periodically send the Hello information to achieve the
following purposes:
Discover neighboring PIM switches.
Judge leaf networks and leaf switches.
Select the designated router (DR) in the multi-access network.
To be compatible with IGMP v1, PIM-DM is in charge of the DR choice. When all PIM neighboring routers on
the interface support DR Priority, the neighboring router with higher priority is selected as the DR. If the priority
is the same, the neighboring router with the maximum interface IP value is selected as the DR. If the priority is
not shown in the Hello message of multiple routers, the router whose interface has the biggest IP value is
selected as the DR.
The PIM-DM v2 of DBCOMs switches supports the neighbor filtration list, CIDR, VLSM and IGMP v1-v3.
50.4.2 Configuring PIM-DM
50.4.2.1 Modifying Timer
The routing protocol adopts several timers to judge the transmission frequency of Hello message and
state-refresh control message. The interval to transmit the Hello message affects whether the neighbor
relationship can correctly created.
Run the following commands in switch configuration mode to regulate the timer:
Command Purpose
ip pim-dm hello-interval
Sets the interval (unit: second) to
send the Hello message from the
interface and the neighbor.
Ippim-dm state-refresh
rigination-interval
For the first-hop switch directly
connecting the source, the interval to
send the state-refresh message is
only valid to the configurations at the
upstream ports. For the following
switches, the interval is the period to
receive and handle the state-refresh
message.