Chapter 20
| Multicast Routing
Configuring PIMv6 for IPv6
– 778 –
continue receiving the flow referenced in the message. (Range: 500-6000
milliseconds; Default: 2500 milliseconds)
The override interval and the propagation delay are used to calculate the LAN
prune delay. If a downstream router has group members which want to
continue receiving the flow referenced in a LAN prune delay message, then the
override interval represents the time required for the downstream router to
process the message and then respond by sending a Join message back to the
upstream router to ensure that the flow is not terminated.
◆ Propagation Delay – The time required for a LAN prune delay message to
reach downstream routers. (Range: 100-5000 milliseconds; Default: 500
milliseconds)
The override interval and pro po gat ion delay are used to calculate the LAN
prune delay. If a downstream router has group members which want to
continue receiving the flow referenced in a LAN prune delay message, then the
propagation delay represents the time required for the LAN prune delay
message to be propagated down from the upstream router to all downstream
routers attached to the same VLAN interface.
◆ Trigger Hello Delay – The maximum time before transmitting a triggered PIM
Hello message after the router is rebooted or PIM is enabled on an interface.
(Range: 0-5 seconds; Default: 5 seconds)
When a router first starts or PIM is enabled on an interface, the hello delay is set
to random value between 0 and the trigger hello delay. This prevents
synchronization of Hello messages on multi-access links if multiple routers are
powered on simultaneously.
Also, if a Hello message is received from a new neighbor, the receiving router
will send its own Hello message after a random delay between 0 and the
trigger hello delay.
Dense-Mode Attributes
◆ Graft Retry Interval – The time to wait for a Graft acknowledgement before
resending a Graft message. (Range: 1-10 seconds; Default: 3 seconds)
A graft message is sent by a router to cancel a prune state. When a router
receives a graft message, it must respond with an graft acknowledgement
message. If this acknowledgement message is lost, the router that sent the
graft message will resend it a number of times (as defined by Max. Graft
Retries).
◆ Max. Graft Retries – The maximum number of times to resend a Graft message
if it has not been acknowledged. (Range: 1-10; Default: 3)
◆ State Refresh Origination Interval – The interval between sending PIM-DM
state refresh control messages. (Range: 1-100 seconds; Default: 60 seconds)
The pruned state times out approximately every three minutes and the entire
PIM-DM network is re-flooded with multicast packets and prune messages. The
state refresh feature keeps the pruned state from timing out by periodically
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