Users Guide

Preventing a PIM Router from Forming an Adjacency
To prevent a router from participating in PIM (for example, to configure stub multicast routing), use the following command.
• Prevent a router from participating in PIM.
INTERFACE mode
ip pim neighbor-filter
Setting a Threshold for Switching to the SPT
The functionality to specify a threshold for switchover to the shortest path trees (SPTs) is available on the system. After a
receiver receives traffic from the RP, PM-SM switches to SPT to forward multicast traffic. Every multicast group has an RP and a
unidirectional shared tree (group-specific shared tree).
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.
Initially, a single PIM-SM tree called a shared tree to distribute traffic. It is called shared because all traffic for the group,
regardless of the source, or the location of the source, must pass through the RP. The shared tree is unidirectional; that is, all
multicast traffic flows only from the RP to the receivers. Once a receiver receives traffic from the RP, PM-SM switches to SPT to
forward multicast traffic, which connects the receiver directly to the source.
You can configure PIM to switch over to the SPT when the router receives multicast packets at or beyond a specified rate.
Table 62. Configuring PIM to Switch Over to the SPT
IPv4 Configure PIM to switch over to the SPT when the
multicast packet rate is at or beyond a specified rate. The
keyword infinity directs PIM to never switch to the SPT.
ip pim spt-threshold {|
infinity}
CONFIGURATION
IPv6 Configure PIM to switch over to the SPT when the
multicast packet rate is at or beyond a specified rate. The
keyword infinity directs PIM to never switch to the SPT.
ip pim spt-threshold {|
infinity}
CONFIGURATION
Preventing a Source from Registering with the RP
To prevent the PIM source DR from sending register packets to route processor (RP) for the specified multicast source and
group, use the following command. If the source DR never sends register packets to the RP, no hosts can ever discover the
source and create a shortest path tree (SPT) to it.
• Prevent a source from transmitting to a particular group.
CONFIGURATION mode
ip pim register-filter
In the following example, Source 1 and Source 2 are both transmitting packets for groups 239.0.0.1 and 239.0.0.2. R3 has a PIM
register filter that only permits packets destined for group 239.0.0.2. An entry is created for group 239.0.0.1 in the routing table,
but no outgoing interfaces are listed. R2 has no filter, so it is allowed to forward both groups. As a result, Receiver 1 receives
only one transmission, while Receiver 2 receives duplicate transmissions.
Multicast Features 549