Chapter 30
| Multicast Routing Commands
PIM Multicast Routing
– 1040 –
Default Setting
The last-hop PIM router joins the shortest path tree immediately after the first
packet arrives from a new source.
Command Mode
Global Configuration
Command Usage
◆ The default path for packets from a multicast source to a receiver is through the
RP. However, the path through the RP is not always the shortest path. Therefore,
the router uses the RP to forward only the first packet from a new multicast
group to its receivers. Afterwards, it calculates the shortest path tree (SPT)
directly between the receiver and source, and then uses the SPT to send all
subsequent packets from the source to the receiver instead of using the shared
tree. Note that when the SPT threshold is not set by this command, the PIM leaf
router will join the shortest path tree immediately after receiving the first
packet from a new source.
◆ This command forces the router to use the shared tree for all multicast groups,
or just for the specified multicast groups.
◆ Only one entry is allowed for this command.
Example
This example prevents the switch from using the SPT for multicast groups
224.1.0.0~224.1.255.255.
Console(config-if)#ip pim sparse-mode
Console(config-if)#exit
Console(config)#ip multicast-routing
Console(config)#router pim
Console(config)#ip pim spt-threshold infinity group-prefix 224.1.0.0
0.0.255.255
Console#
ip pim ssm range This command sets the range for Source-specific Multicast (SSM) addresses. Use the
no form to restore the default setting.
Syntax
ip pim ssm range group-address mask
no ip pim ssm range
group-address - Source-specific multicast group address. The address range
that can be specified is 224.0.0.0 to 239.255.255.255.
mask - Subnet mask that is used for the group address.
Default Setting
232.0.0.0 255.0.0.0
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