User Manual UMN:CLI
V5808
445
9.3.1.8 MRIB Debug
To debug events in the MRIB, use the following command.
debug nsm mcast {all | fib-msg |
mrt | register | stats | vif}
Debugs events in the MRIB.
all: all multicast debugging
fib-msg: MFIB messages
mrt: multicast routes
register: multicast PIM register messages
stats: multicast statistics
vif: multicast interface
no debug nsm mcast { fib-msg |
mrt | register | stats | vif}
Disables the debug event.
9.3.2 PIM Basic
Protocol Independent Multicast (PIM) is the most widely deployed multicast routing
protocol. It may use the underlying unicast routing information base, but is not dependent
on any particular unicast routing protocol. PIM has two operation modes, which are called
PIM Sparse Mode (PIM-SM) and PIM Dense Mode (PIM-DM), each optimized for a
different environment.
PIM-SM is a multicast routing protocol efficient for multicast groups that may span wide-
area (and inter-domain) internets. In the sparse mode, routers forward multicast packets
only when they receives explicit join messages from neighboring routers that have
downstream group members. PIM-SM uses a unidirectional shared tree per group to
deliver multicast traffic, and optionally uses the shortest path tree per source.
PIM-DM is a multicast routing protocol efficient for multicast groups that are densely
populated across a network. In the dense mode, routers initially flood multicast datagrams
to all multicast routers, since they assume that all downstream systems want to receive
multicast packets. Prune messages are then used to prevent from propagating to routers
with no group members. Both PIM protocols use the same message formats.
The V5808 currently support PIM-SM only.
PIM Messages
The followings are simple descriptions of PIM control messages:
• Hello
PIM routers periodically send hello messages on all interfaces to discover neighbor-
ing PIM routers and to determine which router will be the DR for each subnet.
• Register
Register messages are sent by the DR to the RP when a multicast packet needs to
be transmitted on the RPT. These messages may contain the encapsulated multicast
traffic. Both register and register-stop messages are unicast.
• Register-stop
When receiving the register-stop message, routers stop sending register messages.
These messages are sent from the RP to the sender of the register messages.
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