The value of vRtrPimNgIfNeighborGenId indicates a randomly generated 32-bit value that is regenerated each time PIM forwarding is started or restarted on the interface, including when the router itself restarts. When a Hello message with a new vRtrPimNgIfNeighborGenId is received from a neighbor, any old Hello information about that neighbor is discarded and superseded by the information from the new Hello message.
Sources for this description
Netdisco MIB archive copiesNokia networking MIB copies (LibreNMS/Observium Community)