3Com S7902E, Configuration Manual

Page: 1309 / 2621

1-30
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
No matter in an IPv6 PIM-DM domain or an IPv6 PIM-SM domain, the hello messages sent among
routers contain many configurable options, including:
z
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.
z
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.
z
LAN_Prune_Delay: the delay of prune messages on a multi-access network. This option consists
of Lan-delay (namely, message prune 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, the neighbor
tracking feature should be enabled on all IPv6 PIM routers on a multi-access subnet.
The LAN-delay setting will cause the upstream routers to delay processing received prune messages.
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 IPv6 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 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 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 IPv6 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... Use the command... Remarks
Enter system view system-view —