Reference Guide

718 | PIM Sparse-Mode
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Set a Threshold for Switching to the SPT
Set a Threshold for Switching to the SPT is available only on platform: e
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 shortest path trees (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.
PIM-SM Graceful Restart
PIM-SM Graceful Restart is supported only on platform e
PIM-SM Graceful Restart is supported only on platform e
x
with FTOS 8.2.1.0 and later.
When a PIM neighbor restarts and the liveliness timer for that neighbor expires, the join/prune states
received from the neighbor expire, and the corresponding interfaces are removed from the outgoing list of
multicast entries. The effect of this is that active multicast sessions are brought down.
FTOS supports PIM-SM graceful restart based on the GenID. Per RFC 4601, hello messages should
contain a Generation_Identifier option, which contains a randomly generated value (GenID) that is
regenerated each time PIM forwarding is started or restarted on the interface, including when the router
restarts. When a router receives from a neighbor a hello message with a new GenID, any old hello
information about that neighbor should be discarded and superseded by the information from the new hello
message.
FTOS supports graceful restart based on the GenID. A Dell Force10 PIM router announces its graceful
restart capability to its neighbors up front as an option in its hello messages.
If a graceful-restart capable router recognizes that a graceful-restart capable neighbor has restarted, it
preserves the state from the neighbor and continues forwarding multicast traffic while the neighbor
restarts.
IP Version Task Command Syntax Command Mode
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
{value | infinity}
Default: 10 kbps
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
{value | infinity}
Default: 10 kbps
CONFIGURATION