Configuring the state refresh feature

• State refresh capability—Enables the PIM device directly connected to the source to periodically send state refresh messages. It also enables other PIM devices to refresh pruned state timers after receiving the state refresh messages. It prevents the pruned interfaces from resuming multicast forwarding.

• State refresh interval—Determines the interval at which a device sends state refresh messages.

• Wait time before accepting a new state refresh message—A device might receive duplicate state refresh messages within a short time. To prevent this situation, you can configure the time that the device must wait to accept a new state refresh message. If the device receives a new state refresh message before the timer expires, it discards the message. If the device receives a new state refresh message after the timer expires, it accepts the message, refreshes its own PIM-DM state, and resets the waiting timer.

• TTL value of state refresh messages—The TTL value of a state refresh message decrements by 1 whenever it passes a device before it is forwarded to the downstream node. The state refresh message is not forwarded when the TTL value comes down to 0. A state refresh message with a large TTL value might cycle on a small network.

  To effectively control the propagation scope of state refresh messages, configure an appropriate TTL value based on the network size on the device directly connected with the multicast source.

Perform this task on all devices in the PIM-DM domain.

1. Enter system view.

   system-view

2. Enter interface view.

   interface interface-type interface-number

3. Enable the state refresh feature.

   pim state-refresh-capable

   By default, the state refresh feature is enabled.

4. Return to system view.

   quit

5. Enter PIM view.

   pim [ vpn-instance vpn-instance-name ]

6. Set the state refresh interval.

   state-refresh-interval interval

   The default setting is 60 seconds.

   Perform this task on the device directly connected to the multicast source.

7. Set the amount of time that the device must wait to accept a new state refresh message.

   state-refresh-rate-limit time

   The default setting is 30 seconds.

8. Set the TTL value of state refresh messages.

   state-refresh-ttl ttl-value

   The default setting is 255.