pim hello-option neighbor-tracking

Usage Scenario

When sending a Hello message, the switch generates a Generation ID and encapsulates it into the message. The Generation ID changes only when the status of the switch changes. In this case, the neighboring device detects the Generation ID change after receiving the Hello message and immediately sends a Join message to the switch to update the neighbor relationship. If multiple devices on the shared network segment prepare to send Join messages to the same upstream PIM neighbor, only one device is allowed to send the Join message. After other devices detect the Join message, they do not send Join messages to the upstream neighbor. This means that the upstream neighbor cannot update neighbor relationships with downstream devices after a Generation ID change.

After the neighbor tracking function is enabled, when the device detects Join messages from other devices, the device still sends the Join messages to the same upstream PIM neighbor.

Prerequisites

IP multicast routing has been enabled using the multicast routing-enable command.

Precautions

This command is valid for only PIM-SM.

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

The pim hello-option neighbor-tracking command has the same function as the hello-option neighbor-tracking (IPv4) command in the PIM view. By default, if the pim hello-option neighbor-tracking command is not used, the configuration in the PIM view takes effect; otherwise, the configuration in the interface view takes effect.