H3C Technologies H3C S10500 Series Switches - Manual (Page 412)

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NOTE:
With the hello message filter configured, if hello messages of an existing IPv6 PIM neighbor fail to pass the
filter, the IPv6 PIM neighbor will be removed automatically when it times out.
Configuring IPv6 PIM hello options
In either an IPv6 PIM-DM domain or an IPv6 PIM-SM domain, the hello messages sent among routers
contain the following configurable options:
• DR_Priority (for IPv6 PIM-SM only)—Priority for DR election. The higher the priority is, the easier it
is for the router to win DR election. You can configure this parameter on all the routers in a
multi-access network directly connected to IPv6 multicast sources or receivers.
• Holdtime—The timeout time of IPv6 PIM neighbor reachability state. When this timer times out, if
the router has received no hello message from an IPv6 PIM neighbor, it assumes that this neighbor
has expired or become unreachable.
• LAN_Prune_Delay—The delay of prune messages on a multi-access network. This option consists of
LAN-delay (namely, prune message delay), override-interval, and neighbor tracking flag. If the
LAN-delay or override-interval values of different IPv6 PIM routers on a multi-access subnet are
different, the largest value will take effect. If you want to enable neighbor tracking, be sure to
enable the neighbor tracking feature on all IPv6 PIM routers on a multi-access subnet.
The LAN-delay setting will cause the upstream routers to delay forwarding received prune messages. The
override-interval sets the length of time that a downstream router can 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 IPv6 multicast
data, it must send a join message within the prune override interval. Otherwise, the upstream route will
perform the prune action when the period of LAN-delay plus override-interval times out.
A hello message sent from an IPv6 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 an IPv6
PIM router does not change unless the status of the router changes (for example, when IPv6 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 an IPv6 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 that 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, be sure to disable the join
suppression feature on all IPv6 PIM routers on a multi-access subnet. Otherwise, the upstream router will
fail to explicitly track join messages from downstream routers.
Configuring hello options globally
Follow these steps to configure hello options globally:
To do... Use the command... Remarks
Enter system view system-view —
Enter IPv6 PIM view pim ipv6 —
Configure the priority for DR
election
hello-option dr-priority priority
Optional
1 by default