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Configuring an IPv6 PIM hello policy
This feature enables the device to filter IPv6 PIM hello messages by using an ACL that specifies the
packet source addresses. It is used to guard against IPv6 PIM message attacks and to establish
correct IPv6 PIM neighboring relationships.
If hello messages of an existing IPv6 PIM neighbor are filtered out by the policy, the neighbor is
automatically removed when its aging timer expires.
To configure an IPv6 PIM hello policy:
Step
Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter interface view.
interface interface-type
interface-number
N/A
3.
Configure an IPv6 PIM
hello policy.
ipv6
pim
neighbor-policy ipv6-acl-number
By default, no IPv6 PIM hello
policy exists on an interface,
and all IPv6 PIM hello
messages are regarded as
legal.
Configuring IPv6 PIM hello message options
In either an IPv6 PIM-DM domain or an IPv6 PIM-SM domain, hello messages exchanged among
routers contain the following configurable options:
•
DR_Priority
(for IPv6 PIM-SM only)—Priority for DR election. The device with the highest
priority wins the DR election. You can configure this option for all the routers in a shared-media
LAN that directly connects to the IPv6 multicast source or the receivers.
•
Holdtime
—IPv6 PIM neighbor lifetime. If a router receives no hello message from a neighbor
when the neighbor lifetime expires, it regards the neighbor failed or unreachable.
•
LAN_Prune_Delay
—Delay of pruning a downstream interface on a shared-media LAN. This
option has LAN delay, override interval, and neighbor tracking support (the capability to disable
join message suppression).
The LAN delay defines the IPv6 PIM message propagation delay. The override interval defines
a time period for a downstream router to override a prune message. If the propagation delay or
override interval on different IPv6 PIM routers on a shared-media LAN are different, the largest
ones apply.
On the shared-media LAN, the propagation delay and override interval are used as follows:
If a router receives a prune message on its upstream interface, it means that there are
downstream routers on the shared-media LAN. If this router still needs to receive multicast
data, it must send a join message to override the prune message within the override
interval.
When a router receives a prune message from its downstream interface, it does not
immediately prune this interface. Instead, it starts a timer (the propagation delay plus the
override interval). If interface receives a join message before the timer expires, the router
does not prune the interface. Otherwise, the router prunes the interface.
If you enable neighbor tracking on an upstream router, this router can track the states of the
downstream nodes for which the joined state holdtime timer has not expired. If you want to
enable neighbor tracking, you must enable it on all IPv6 PIM routers on a shared-media LAN.
Otherwise, the upstream router cannot track join messages from every downstream routers.
•
Generation ID
—A router generates a generation ID for hello messages when an interface is
enabled with IPv6 PIM. The generation ID is a random value, but only changes when the status
of the router changes. If an IPv6 PIM router finds that the generation ID in a hello message from
