Enabling Downstream Neighbor Tracking

When sending a Hello message, a PIM device generates a Generation ID and adds it to the message. If the status of the device changes, the device generates a new Generation ID. When a neighboring device receives the Hello message and finds that the Generation ID has changed, it sends a Join message to refresh the neighbor relationship. Devices on a shared network segment use a listening mechanism to prevent multiple devices from simultaneously sending Join messages to the same upstream device. When a device detects the Join message sent from another device to an upstream device, it does not send Join messages to this upstream PIM device. Therefore, the upstream PIM neighbor with a changed Generation ID cannot refresh neighbor relationships with each downstream neighbor.

After the neighbor tracking function is enabled, PIM devices no longer trigger Join message suppression when they detect a Join message sent by another PIM device. Instead, they keep sending Join messages to the same upstream neighbor.

The neighbor tracking function can be enabled globally or on an interface. If this function is configured in both the global PIM view and interface view, the configuration in the interface view takes effect.

The neighbor tracking function can be implemented only when all the devices on the shared network segment have this function enabled.