Configuring PIM hello message options
About PIM hello message options
In either a PIM-DM domain or a PIM-SM domain, hello messages exchanged among devices contain the following configurable options:
DR_Priority (for 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 devices in a shared-media LAN that directly connects to the multicast source or the receivers.
Holdtime—PIM neighbor lifetime. If a device does not receive a 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 the LAN delay field, the override interval field, and the T bit.
The LAN delay defines the PIM message propagation delay. The override interval defines a period for a device to override a prune message. The T bit specifies the capability of tracking downstream device status on upstream devices.
On the shared-media LAN, the propagation delay and override interval are used as follows:
If a device receives a prune message on its upstream interface, it means that there are downstream devices on the shared-media LAN. If this device still needs to receive multicast data, it must send a join message to override the prune message within the override interval.
When a device 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 device does not prune the interface. Otherwise, the device prunes the interface.
Neighbor tracking—If you enable neighbor tracking on an upstream device, this device can track the states of the downstream nodes for which the joined state holdtime timer has not expired. All join messages from downstream devices are accepted.
Restrictions and guidelines
If the propagation delay or override interval on different PIM devices on a shared-media LAN are different, the largest ones apply.
If you want to enable neighbor tracking, you must enable it on all PIM devices on a shared-media LAN. Otherwise, the upstream device cannot track join messages from every downstream devices.
You can configure hello message options for all interfaces in PIM view or for the current interface in interface view. The configuration made in interface view takes priority over the configuration made in PIM view.
Configuring hello message options globally
Enter system view.
system-view
Enter PIM view.
pim [ vpn-instance vpn-instance-name ]
Set the DR priority.
hello-option dr-priority priority
The default setting is 1.
Set the neighbor lifetime.
hello-option holdtime time
The default setting is 105 seconds.
Set the PIM message propagation delay for a shared-media LAN.
hello-option lan-delay delay
The default setting is 500 milliseconds.
Set the override interval.
hello-option override-interval interval
The default setting is 2500 milliseconds.
Enable neighbor tracking.
hello-option neighbor-tracking
By default, neighbor tracking is disabled.
Configuring hello message options on an interface
Enter system view.
system-view
Enter interface view.
interface interface-type interface-number
Set the DR priority.
pim hello-option dr-priority priority
The default setting is 1.
Set the neighbor lifetime.
pim hello-option holdtime time
The default setting is 105 seconds.
Set the PIM message propagation delay.
pim hello-option lan-delay delay
The default setting is 500 milliseconds.
Set the override interval.
pim hello-option override-interval interval
The default setting is 2500 milliseconds.
Enable neighbor tracking.
pim hello-option neighbor-tracking
By default, neighbor tracking is disabled.