PIM Sparse-Mode (PIM-SM)
PIM Sparse-Mode (PIM-SM)
PIM-Sparse Mode (PIM-SM) is a multicast protocol that forwards multicast traffic to a subnet only upon
request using a PIM Join message; this behavior is the opposite of PIM-Dense Mode, which forwards
multicast traffic to all subnets until a request to stop.
Implementation Information
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The Dell Force10 implementation of PIM-SM is based on the IETF Internet Draft
draft-ietf-pim-sm-v2-new-05.
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C-Series supports a maximum of 31 PIM interfaces and 4K multicast entries including (*,G), and
(S,G) entries. There is no limit on the number of PIM neighbors C-Series can have.
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S-Series supports a maximum of 31 PIM interfaces and 2K multicast entries including (*,G), and (S,G)
entries. There is no limit on the number of PIM neighbors S-Series can have.
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E-Series supports a maximum of 511 PIM interfaces and 50K multicast entries including (*,G), (S,G),
and (S,G,rpt) entries. There is no limit on the number of PIM neighbors E-Series can have.
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The SPT-Threshold is zero, which means that the last-hop designated router (DR) joins the shortest
path tree (SPT) to the source upon receiving the first multicast packet.
•
FTOS reduces the number of control messages sent between multicast routers by bundling Join and
Prune requests in the same message.
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FTOS supports PIM-SM on physical, VLAN, and port-channel interfaces.
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FTOS supports 2000 IPv6 multicast forwarding entries, with up to 128 PIM-SSM neighbors/interfaces.
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PIM-SM on VLAN interfaces is supported on the E-Series on TeraScale platforms only.
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IPv6 Multicast is not supported on SONET interfaces.
Protocol Overview
PIM-SM initially uses unidirectional shared trees to forward multicast traffic; that is, all multicast traffic
must flow only from the Rendezvous Point (RP) to the receivers. Once a receiver receives traffic from the
RP, PM-SM switches to shortest path trees (SPT) to forward multicast traffic. Every multicast group has an
RP and a unidirectional shared tree (group-specific shared tree).
is supported on platforms:
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