Single actual-forwarder election in multicast VPNs

A first ingress network device comprising:

• at least one computer processor;
• and
• a memory comprising instructions that when executed by the at least one computer processor cause the at least one computer processor to:
• receive a source tree join route message from an egress network device of a network, the source tree join route message specifying a multicast source and a multicast group;
• in response to receiving a first source active auto-discovery route message from a second ingress network device of the network indicating that the second ingress network device has switched from using a shared multicast tree to using a shortest path tree to deliver multicast traffic from the multicast source, elect one of the first ingress network device or the second ingress network device as a single active forwarder for forwarding the multicast traffic received from the multicast source for the multicast group;
• defer sending a second source active auto-discovery route message indicating that the first ingress network device discovered the multicast source responsive to the source tree join route message until determining that the first ingress network device is receiving multicast traffic from the multicast source for the multicast group;
• and
• in response to determining that the first ingress network device is receiving multicast traffic from the multicast source for the multicast group, send the second source active auto-discovery route message indicating that the first ingress network device discovered the multicast source.

A non-transitory computer-readable storage medium encoded with instructions that, when executed, cause at least one processor of a first ingress network device to:

• receive a source tree join route message from an egress network device, the source tree join route message specifying a multicast source and a multicast group;
• in response to receiving a first source active auto-discovery route message from a second ingress network device of the network indicating that the second ingress network device has switched from using a shared multicast tree to using a shortest path tree to deliver multicast traffic from the multicast source, elect one of the first ingress network device or the second ingress network device as a single active forwarder for forwarding the multicast traffic received from the multicast source for the multicast group;
• defer sending a second source active auto-discovery route message indicating that the first ingress network device discovered the multicast source responsive to the source tree join route message until determining that the first ingress network device is receiving multicast traffic from the multicast source for the multicast group;
• and
• in response to determining that the first ingress network device is receiving multicast traffic from the multicast source for the multicast group, send the second source active auto-discovery route message indicating that the first ingress network device discovered the multicast source.