Adjusting Control Parameters for State-Refresh

In a PIM-DM network, the periodic flooding-pruning wastes lots of network resources. To prevent the pruned interface from forwarding messages because the prune timer times out, you can enable the State-Refresh function. The multicast device then sends State-Refresh messages periodically to refresh the prune state of the interface and maintain the shortest path tree (SPT).

Disabling State-Refresh: After this function is disabled on the interface, the interface cannot forward any State-Refresh messages.

Configuring the Interval for Sending State-Refresh Messages: To prevent pruned interfaces from forwarding messages after the prune state timer times out, you need to set the interval for sending State-Refresh messages to be shorter than the period for keeping the Prune state.

Configuring the Period for Receiving the Next State-Refresh Message: A multicast device may receive PIM State-Refresh messages from multiple routers in a short period and some PIM State-Refresh messages are repeated. Before the state-refresh timer times out, the device discards the received repeated State-Refresh messages. The device is allowed to receive the next State-Refresh message only after the timer times out.

Configuring the TTL Value Carried in a State-Refresh Message: After receiving the PIM State-Refresh message, a multicast device decrements the TTL value by 1 and then forwards the message downstream until the TTL value becomes 0. In a small-sized network, the PIM State-Refresh message is transmitted circularly on the network. You can adjust the TTL value according to the network scale.