Alcatel-Lucent 6850-48 参考指南
OmniSwitch CLI Reference Guide
September 2009
page 45-1
45 PIM Commands
Protocol-Independent Multicast (PIM) is an IP multicast routing protocol that uses routing information
provided by unicast routing protocols, such as RIP and OSPF. Note that PIM is not dependent on any
particular unicast routing protocol. Sparse mode PIM (PIM-SM) contrasts with flood-and-prune dense
mode multicast protocols, such as DVMRP and PIM Dense Mode (PIM-DM), in that multicast forward-
ing in PIM-SM is initiated only via specific requests.
provided by unicast routing protocols, such as RIP and OSPF. Note that PIM is not dependent on any
particular unicast routing protocol. Sparse mode PIM (PIM-SM) contrasts with flood-and-prune dense
mode multicast protocols, such as DVMRP and PIM Dense Mode (PIM-DM), in that multicast forward-
ing in PIM-SM is initiated only via specific requests.
Downstream routers must explicitly join PIM-SM distribution trees to receive multicast streams on behalf
of directly connected receivers or other downstream PIM-SM routers. This paradigm of receiver-initiated
forwarding makes PIM ideal for network environments where receiver groups are thinly populated and
bandwidth conservation is a concern, such as in wide area networks (WANs). PIM-DM uses RPF (Reverse
Path Forwarding) to prevent looping of multicast datagrams while flooding. If some areas of the network
do not have group members, PIM-DM will prune the forwarding branch by instantiating the prune state.
of directly connected receivers or other downstream PIM-SM routers. This paradigm of receiver-initiated
forwarding makes PIM ideal for network environments where receiver groups are thinly populated and
bandwidth conservation is a concern, such as in wide area networks (WANs). PIM-DM uses RPF (Reverse
Path Forwarding) to prevent looping of multicast datagrams while flooding. If some areas of the network
do not have group members, PIM-DM will prune the forwarding branch by instantiating the prune state.
PIM-DM differs from PIM-SM in two essential ways:
• There are no periodic joins transmitted, only explicitly triggered prunes and grafts.
• There is no Rendezvous Point (RP). This is particularly important in networks that cannot tolerate a
single point of failure.
Alcatel-Lucent implementation of PIM can also be configured in an IPv6 environment.
MIB information for the PIM commands is as follows:
Filename: AlcatelIND1Pim_mib.htm
Module: ALCATEL-IND1-PIM-MIB
Module: ALCATEL-IND1-PIM-MIB
Filename: IETF_PIM_BSR.mib
Module: PIM-BSR-MIB
Module: PIM-BSR-MIB
Filename: IETF_PIM_STD.mib
Module: PIM-STD-MIB
Module: PIM-STD-MIB