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Refuse Multicast Traffic
A host requesting to leave a multicast group sends an IGMP Leave message to the last-hop DR. If the host is the only remaining
receiver for that group on the subnet, the last-hop DR is responsible for sending a PIM Prune message up the RPT to prune its
branch to the RP.
1.
After receiving an IGMP Leave message, the gateway removes the interface on which it is received from the outgoing interface
list of the (*,G) entry. If the (*,G) entry has no remaining outgoing interfaces, multicast traffic for that group is no longer
forwarded to that subnet.
2.
If the (*,G) entry has no remaining outgoing interfaces, the last-hop DR sends a PIM Prune message to towards the RP. All
routers along the way remove the interface on which the message was received from the outgoing interface list of the (*,G)
entry. If on any router there is at least one outgoing interface listed for that (*,G) entry, the Prune message is not forwarded.
Send Multicast Traffic
With PIM-SM, all multicast traffic must initially originate from the RP. A source must unicast traffic to the RP so that the RP can
learn about the source and create an SPT to it. Then the last-hop DR may create an SPT directly to the source.
1.
The source gateway router (first-hop DR) receives the multicast packets and creates an (S,G) entry in its multicast routing
table. The first-hop DR encapsulates the initial multicast packets in PIM Register packets and unicasts them to the RP.
2.
The RP decapsulates the PIM Register packets and forwards them if there are any receivers for that group. The RP sends a
PIM Join message towards the source. All routers between the RP and the source, including the RP, create an (S,G) entry and
list the interface on which the message was received as an outgoing interface, thus recreating a SPT to the source.
3.
After the RP starts receiving multicast traffic via the (S,G), it unicasts a Register-Stop message to the first-hop DR so that
multicast packets are no longer encapsulated in PIM Register packets and unicast. After receiving the first multicast packet
from a particular source, the last-hop DR sends a PIM Join message to the source to create an SPT to it.
4.
There are two paths, then, between the receiver and the source, a direct SPT and an RPT. One router receives a multicast
packet on two interfaces from the same source in this case; this router prunes the shared tree by sending a PIM Prune
message to the RP that tells all routers between the source and the RP to remove the outgoing interface from the (*,G) entry,
and tells the RP to prune its SPT to the source with a Prune message.
Dell Networking OS Behavior
: When the router creates an SPT to the source, there are then two paths between the receiver and
the source, the SPT and the RPT. Until the router can prune itself from the RPT, the receiver receives duplicate multicast packets
which may cause disruption. Therefore, the router must prune itself from the RPT as soon as possible. Dell Networking OS optimizes
the shared to shortest-path tree switchover latency by copying and forwarding the first (S,G) packet received on the SPT to the
PIM task immediately upon arrival. The arrival of the (S,G) packet confirms for PIM that the SPT is created, and that it can prune
itself from the shared tree.
Important Point to Remember
If you use a Loopback interface with a /32 mask as the RP, you must enable PIM Sparse-mode on the interface.
Configuring PIM-SM
Configuring PIM-SM is a three-step process.
1.
Enable multicast routing (refer to the following step).
2.
Select a rendezvous point.
3.
Enable PIM-SM on an interface.
Enable multicast routing.
CONFIGURATION mode
PIM Sparse-Mode (PIM-SM)
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Содержание S4048-ON
Страница 1: ...Dell Configuration Guide for the S4048 ON System 9 9 0 0 ...
Страница 146: ...Figure 14 BFD Three Way Handshake State Changes 146 Bidirectional Forwarding Detection BFD ...
Страница 477: ...Figure 68 Inspecting Configuration of LAG 10 on ALPHA Link Aggregation Control Protocol LACP 477 ...
Страница 480: ...Figure 70 Inspecting a LAG Port on BRAVO Using the show interface Command 480 Link Aggregation Control Protocol LACP ...
Страница 481: ...Figure 71 Inspecting LAG 10 Using the show interfaces port channel Command Link Aggregation Control Protocol LACP 481 ...
Страница 522: ...Figure 87 Configuring Interfaces for MSDP 522 Multicast Source Discovery Protocol MSDP ...
Страница 523: ...Figure 88 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 523 ...
Страница 524: ...Figure 89 Configuring PIM in Multiple Routing Domains 524 Multicast Source Discovery Protocol MSDP ...
Страница 528: ...Figure 91 MSDP Default Peer Scenario 1 528 Multicast Source Discovery Protocol MSDP ...
Страница 529: ...Figure 92 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 529 ...
Страница 530: ...Figure 93 MSDP Default Peer Scenario 3 530 Multicast Source Discovery Protocol MSDP ...
Страница 633: ...Policy based Routing PBR 633 ...
Страница 777: ...Figure 119 Single and Double Tag TPID Match Service Provider Bridging 777 ...
Страница 778: ...Figure 120 Single and Double Tag First byte TPID Match 778 Service Provider Bridging ...