3com 8807 Guia Do Utilizador
464
C
HAPTER
44: PIM-SM C
ONFIGURATION
sent to leaf routers along the path built and then reach the hosts. In this way, an
RP-rooted tree (RPT) is built as shown in Figure 8-1.
RP-rooted tree (RPT) is built as shown in Figure 8-1.
Figure 112 RPT schematic diagram
Multicast source registration
When multicast source S sends a multicast packet to the multicast group G, the
PIM-SM multicast router directly connected to S will encapsulate the received
packet into a registration packet and send it to the corresponding RP in unicast
form. If there are multiple PIM-SM multicast routers on a network segment, the
Designated Router (DR) will be responsible for sending the multicast packet.
PIM-SM multicast router directly connected to S will encapsulate the received
packet into a registration packet and send it to the corresponding RP in unicast
form. If there are multiple PIM-SM multicast routers on a network segment, the
Designated Router (DR) will be responsible for sending the multicast packet.
Preparations before
Configuring PIM-SM
Configuring candidate RPs
In a PIM-SM network, multiple RPs (candidate-RPs) can be configured. Each
Candidate-RP (C-RP) is responsible for forwarding multicast packets with the
destination addresses in a certain range. Configuring multiple C-RPs is to
implement load balancing of the RP. These C-RPs are equal. All multicast routers
calculate the RPs corresponding to multicast groups according to the same
algorithm after receiving the C-RP messages that the BSR advertises.
Candidate-RP (C-RP) is responsible for forwarding multicast packets with the
destination addresses in a certain range. Configuring multiple C-RPs is to
implement load balancing of the RP. These C-RPs are equal. All multicast routers
calculate the RPs corresponding to multicast groups according to the same
algorithm after receiving the C-RP messages that the BSR advertises.
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CAUTION: One RP can serve multiple multicast groups or all multicast groups.
Each multicast group can correspond to one unique RP at a time rather than
multiple RPs.
Each multicast group can correspond to one unique RP at a time rather than
multiple RPs.
Configuring BSRs
The BSR is the management core in a PIM-SM network. Candidate-RPs send
announcement to the BSR, which is responsible for collecting and advertising the
information about all candidate-RPs.
announcement to the BSR, which is responsible for collecting and advertising the
information about all candidate-RPs.
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CAUTION: There can be only one BSR in a network but you can configure multiple
candidate-BSRs. In this case, once a BSR fails, you can switch over to another BSR.
A BSR is elected among the C-BSRs automatically. The C-BSR with the highest
priority is elected as the BSR. If the priority is the same, the C-BSR with the largest
IP address is elected as the BSR.
candidate-BSRs. In this case, once a BSR fails, you can switch over to another BSR.
A BSR is elected among the C-BSRs automatically. The C-BSR with the highest
priority is elected as the BSR. If the priority is the same, the C-BSR with the largest
IP address is elected as the BSR.
Configuring static RP
The router that serves as the RP is the core router of multicast routes. If the
dynamic RP elected by BSR mechanism is invalid for some reason, the static RP can
be configured to specify RP. As the backup of dynamic RP, static RP improves
dynamic RP elected by BSR mechanism is invalid for some reason, the static RP can
be configured to specify RP. As the backup of dynamic RP, static RP improves
Multicast Source S
RPT
join
Multicast source registration
RP
Receiver