User's Manual

48-9
and reach the host. In this way the RPT with RP as root is generated.
(2) Multicast Source Registration
When a Multicast Source S sends a Multicast packet to Multicast Group G, the PIM-SM Multicast
router connected to it directly will take charge of encapsulating the Multicast packet into registered
message and unicast it to corresponding RP. If there are more than one PIM-SM Multicast routers on
a network segment, then DR (Designated Router) takes charge of sending the Multicast packet.
(3) SPT Switch
When the Multicast router finds that the rate of the Multicast packet from RP with destination address
G exceeds threshold, the Multicast router will send Join message to the next upper lever nodes in
the source direction, which results in the switch from RPT to SPT.
2. Preparation before PIM-SM configuration
(1) Configuration Candidate RP
More than one RPs (candidate RP) can exist in PIM-SM network and each C-RP (Candidate RP)
takes charge of transmitting Multicast packets with destination address in a certain range. To
configure more than one candidate RPs can implement RP load share. No master or slave is
differentiated among RPs. All Multicast routers work out the RP corresponding to some Multicast
group based on the same algorithm after receiving the candidate RP message announced by BSR.
Note that one RP can serve more than one Multicast groups and all Multicast groups. Each Multicast
group can only correspond to one unique RP at any moment. It can’t correspond to more than one
RP at the same time.
(2) Configure BSR
BSR is the management center of PIMSM network. It is in charge of collecting messages sent by
candidate RPs and broadcast them.
Only one BSR can exist within a network, but more than one C-BSR (Candidate-BSR) can be
configured. In this way, if some BSR goes wrong, it can switch to another. C-BSRs elect BSR
automatically.
48.3.2 PIM-SM Configuration Task List
1. Enable PIM-SM (Required)
2. Configure static multicast routing entries (Optional)
3. Configure additional parameters for PIM-SM (Optional)
(1) Configure parameters for PIM-SM interfaces
1) Configure the interval for PIM-SM hello messages
2) Configure the hold time for PIM-SM hello messages
3) Configure ACL for PIM-SM neighbors
4) Configure the interface as the boundary interface of the PIM-SM protocol
5) Configure the interface as the management boundary of the PIM-SM protocol
(2) Configure global PIM-SM parameters
1) Configure the switch as a candidate BSR
2) Configure the switch as a candidate RP
3) Configure static RP
4) Configure the cache time of kernel multicast route
4. Disable PIM-SM Protocol