value randomizes the transmission delay to a time between 0 and the
hello delay
setting. Using 0 means no
delay.
After the router sends the initial hello packet to a newly detected VLAN interface, it sends subsequent hello
packets according to the current
Hello Interval
setting.
Not used with the
no
form of the
ip pim
command.
(Default: 5 seconds)
Enabling or disabling lan prune delay
Syntax:
ip pim-sparse lan-prune-delay
no ip pim-sparse lan-prune-delay
vlan [
vid
] ip pim-sparse lan-prune-delay
no vlan [
vid
] ip pim-sparse lan-prune-delay
Enables the LAN prune delay option on the current VLAN. With
lan-prune-delay
enabled, the router informs
downstream neighbors how long it will wait before pruning a flow after receiving a prune request.
Other downstream routers on the same VLAN must send a join to override the prune before the
lan-prune-
delay
time if they want the flow to continue. This prompts any downstream neighbors with multicast receivers
continuing to belong to the flow to reply with a join. If no joins are received after the
lan-prune-delay
period,
the router prunes the flow.
The
propagation-delay
and
override-interval
settings (below) determine the
lan-prune-delay
setting.
Uses the
no
form of the command to disable the
LAN prune delay
option.
(Default: Enabled)
Changing the
Lan-prune-delay
interval
Syntax:
ip pim-sparse propagation-delay [250-2000]
vlan [
vid
] ip pim-sparse propagation-delay [250-2000]
ip pim-sparse override-interval [500-6000]
vlan [
vid
] ip pim-sparse override-interval [500-6000]
A router sharing a VLAN with other multicast routers uses these two values to compute the
lan-prune-delay
setting (above) for how long to wait for a PIM-SM join after receiving a prune packet from downstream for a
particular multicast group.
Multiple routers sharing VLAN
A network may have multiple routers sharing VLAN "X." When an upstream router is forwarding traffic from
multicast group "X" to VLAN "Y," if one of the routers on VLAN "Y" does not want this traffic, it issues a prune
response to the upstream neighbor. The upstream neighbor then goes into a
prune pending
state for group "X"
on VLAN "Y." (During this period, the upstream neighbor continues to forward the traffic.) During the
pending
period, another router on VLAN "Y" can send a group "X" join to the upstream neighbor. If this happens, the
upstream neighbor drops the
prune pending
state and continues forwarding the traffic. But if no routers on the
VLAN send a join, the upstream router prunes group "X" from VLAN "Y" when the
lan-prune-delay
timer
expires.
Chapter 4 PIM-SM (Sparse Mode)
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