H3C LS-3100-52P-OVS-H3 Operation Manual page 983

largest value will take effect. If you want to enable neighbor tracking, the neighbor tracking feature
should be enabled on all PIM routers on a multi-access subnet.
The LAN-delay setting will cause the upstream routers to delay processing received prune messages. If
the LAN-delay setting is too small, it may cause the upstream router to stop forwarding multicast
packets before a downstream router sends a prune override message. Therefore, be cautious when
configuring this parameter.
The override-interval sets the length of time a downstream router is allowed to wait before sending a
prune override message. When a router receives a prune message from a downstream router, it does
not perform the prune action immediately; instead, it maintains the current forwarding state for a period
of LAN-delay plus override-interval. If the downstream router needs to continue receiving multicast data,
it must send a prune override message within the prune override interval; otherwise, the upstream route
will perform the prune action when the period of LAN-delay plus override-interval time out.
A hello message sent from a PIM router contains a generation ID option. The generation ID is a random
value for the interface on which the hello message is sent. Normally, the generation ID of a PIM router
does not change unless the status of the router changes (for example, when PIM is just enabled on the
interface or the device is restarted). When the router starts or restarts sending hello messages, it
generates a new generation ID. If a PIM router finds that the generation ID in a hello message from the
upstream router has changed, it assumes that the status of the upstream neighbor is lost or the
upstream neighbor has changed. In this case, it triggers a join message for state update.
If you disable join suppression (namely, enable neighbor tracking), the join suppression feature should
be disabled on all PIM routers on a multi-access subnet; otherwise, the upstream router will fail to
explicitly track which downstream routers are joined to it.
Configuring hello options globally
Follow these steps to configure hello options globally:
To do...
Enter system view
Enter PIM view
Configure the priority for DR
election
Configure PIM neighbor
timeout time
Configure the prune delay time
(LAN-delay)
Configure the prune override
interval
Disable join suppression
Configuring hello options on an interface
Follow these steps to configure hello options on an interface:
Use the command...
system-view
pim
hello-option dr-priority
priority
hello-option holdtime interval
hello-option lan-delay interval
hello-option override-interval
interval
hello-option
neighbor-tracking
1-32
Remarks
—
—
Optional
1 by default
Optional
105 seconds by default
Optional
500 milliseconds by default
Optional
2,500 milliseconds by default
Required
Enabled by default