Adjusting Control Parameters for Maintaining Neighbor Relationships
PIM devices exchange Hello messages to set up neighbor
relationships and negotiate various control parameters for controlling
the neighbor relationships.
The interval for sending Hello messages can be set either globally or on an interface. The configuration in the interface view is prior to the configuration in the PIM view. When the interval is not configured in the interface view, the configuration in the PIM view takes effect.
The timeout period of a neighbor can be set either globally or on an interface. If the multicast device does not receive any Hello message from a neighbor when the timeout period is expired, the device considers that the neighbor is unreachable. The timeout period of the neighbor must be longer than the interval for sending Hello messages.
When the Generation ID option in the Hello message received from an upstream neighbor changes, it indicates that the status of the upstream neighbor changes. Therefore, you can configure a PIM interface to deny the Hello messages without Generation ID options to obtain the upstream neighbor status in real time.
To prevent some unknown devices from being involved in PIM, filtering PIM neighbors is required. An interface sets up neighbor relationships with only the addresses matching the filtering rules and deletes the neighbors unmatched with the filtering rules.