Multicast join message processing by multi-homing devices in an ethernet VPN

1. A method comprising:

receiving, by a first provider edge (PE) device of a layer 3 network, configuration data configuring the first PE device to provide, via an Ethernet segment with an edge device, active-active multi-homing layer 2 (L2) virtual bridge connectivity to the edge device using an Ethernet Virtual Private Network (EVPN) instance;

receiving, by the first PE device, a multicast Join message for multicast traffic, the multicast Join message identifying a second PE device that also participates in the EVPN instance, wherein the first PE device is not specified as an upstream neighbor in the multicast Join message;

processing, by the first PE device, the multicast Join message to generate multicast forwarding state; and

forwarding, by the first PE device based at least on the multicast forwarding state, the multicast traffic.

2. The method of claim 1 , further comprising:

applying, by the first PE device based at least on a protocol for the multicast Join message, a policy that specifies one or more acceptable source devices for the protocol; and

accepting and processing, by the first PE device, the multicast Join message in response to determining a source device for the multicast Join message is one of the one more acceptable source devices for the protocol.

3. The method of claim 1 , wherein the multicast Join message comprises an upstream neighbor address field that does not have a value of a network address of the first PE device.

4. The method of claim 1 , wherein forwarding the multicast traffic comprises forwarding, by the first PE device in response to determining the first PE device is a designated forwarder for the EVPN instance for the Ethernet segment, the multicast traffic on the Ethernet segment to the edge device.

5. The method of claim 1 , wherein forwarding the multicast traffic comprises forwarding, by the first PE device, the multicast traffic to a third PE device that is a designated forwarder for the EVPN instance for the Ethernet segment.

6. The method of claim 1 , further comprising:

prior to receiving the multicast Join message, sending, by the first PE device, the multicast traffic to a rendezvous-point (RP) router in Register messages;

after forwarding the multicast traffic based at least on the multicast forwarding state, receiving, by the first PE device, a Register-Stop message; and

reconfiguring, by the first PE device in response to receiving the Register-Stop message, the first PE device to no longer send the multicast traffic to the RP router in Register messages.

7. The method of claim 6 , wherein the reconfiguring comprises deleting a tunnel interface for outputting the multicast traffic via a tunnel to the RP router.

8. The method of claim 6 , wherein the first PE device is a designated router for a multicast source of the multicast traffic.

9. The method of claim 1 , wherein the forwarding comprises forwarding, by the first PE device, the multicast traffic on a shortest-path tree from the first PE device to a rendezvous-point (RP) router.

10. The method of claim 1 , wherein the forwarding comprises forwarding, by the first PE device, the multicast traffic on a shortest-path tree from the first PE device to a designated router for a multicast receiver for the multicast traffic, the method further comprising:

receiving, by the first PE device, a multicast Prune message for the multicast traffic;

by the first PE device in response to receiving the multicast Prune message, reconfiguring the first PE device to no longer forward the multicast traffic on an interface toward a rendezvous-point (RP) router.

11. The method of claim 1 ,

wherein the Join message is originated by a designated router of a multicast receiver for the multicast traffic, and

wherein the multicast forwarding state generated by processing the multicast Join message comprises multicast forwarding state for a shortest-path tree to the designated router of the multicast receiver.

12. A network device operable as a first provider edge (PE) device of a layer 3 network, comprising:

one or more processors operably coupled to a memory,

wherein the one or more processors are configured to receive configuration data configuring the first PE device to provide, via an Ethernet segment with an edge device, active-active multi-homing layer 2 (L2) virtual bridge connectivity to the edge device using an Ethernet Virtual Private Network (EVPN) instance,

wherein the one or more processors are configured to receive a multicast Join message for multicast traffic, the multicast Join message identifying a second PE device that also participates in the EVPN instance, wherein the first PE device is not specified as an upstream neighbor in the multicast Join message,

wherein the one or more processors are configured to process the multicast Join message to generate multicast forwarding state, and

wherein the one or more processors are configured to forward, based at least on the multicast forwarding state, the multicast traffic.

13. The network device of claim 12 ,

wherein the one or more processors are configured to apply, based at least on a protocol for the multicast Join message, a policy that specifies one or more acceptable source devices for the protocol, and

wherein the one or more processors are configured to accept and process the multicast Join message in response to determining a source device for the multicast Join message is one of the one more acceptable source devices for the protocol.

14. The network device of claim 12 , wherein the multicast Join message comprises an upstream neighbor address field that does not have a value of a network address of the first PE device.

15. The network device of claim 12 , wherein the one or more processors are configured to forward, in response to a determination the first PE device is a designated forwarder for the EVPN instance for the Ethernet segment, the multicast traffic on the Ethernet segment to the edge device.

16. The network device of claim 12 , wherein the one or more processors are configured to forward the multicast traffic to a third PE device that is a designated forwarder for the EVPN instance for the Ethernet segment.

17. The network device of claim 12 , further comprising:

wherein the one or more processors are configured to, prior to receipt of the multicast Join message, send the multicast traffic to a rendezvous-point (RP) router in Register messages,

wherein the one or more processors are configured to, after forwarding the multicast traffic based at least on the multicast forwarding state, receive a Register-Stop message, and

wherein the one or more processors are configured to reconfigure, in response to receipt of the Register-Stop message, the first PE device to no longer send the multicast traffic to the RP router in Register messages.

18. The network device of claim 17 , wherein the one or more processors are configured to delete a tunnel interface for outputting the multicast traffic via a tunnel to the RP router.

19. The network device of claim 17 , wherein the first PE device is a designated router for a multicast source of the multicast traffic.

20. The network device of claim 12 , wherein the one or more processors are configured to forward the multicast traffic on a shortest-path tree from the first PE device to a rendezvous-point (RP) router.

21. The network device of claim 12 ,

wherein the one or more processors are configured to forward the multicast traffic on a shortest-path tree from the first PE device to a designated router for a multicast receiver for the multicast traffic,

wherein the one or more processors are configured to receive a multicast Prune message for the multicast traffic;

wherein the one or more processors are configured to, in response to receipt of the multicast Prune message, reconfigure the first PE device to no longer forward the multicast traffic on an interface toward a rendezvous-point (RP) router.

22. The network device of claim 12 ,

wherein the Join message is originated by a designated router of a multicast receiver for the multicast traffic, and

wherein the multicast forwarding state generated by processing the multicast Join message comprises multicast forwarding state for a shortest-path tree to the designated router of the multicast receiver.

23. A non-transitory computer-readable medium comprising instructions for causing one or more programmable processors of a provider edge (PE) device of a layer 3 network to:

receive configuration data configuring the PE device to provide, via an Ethernet segment with an edge device, active-active multi-homing layer 2 (L2) virtual bridge connectivity to the edge device using an Ethernet Virtual Private Network (EVPN) instance;

receive a multicast Join message for multicast traffic, the multicast Join message identifying a different PE device that also participates in the EVPN instance;

process the multicast Join message to generate multicast forwarding state; and

forward, based at least on the multicast forwarding state, the multicast traffic.

24. The method of claim 1 , wherein the multicast Join message comprises a Protocol Independent Multicast Join message.

25. The network device of claim 12 , wherein the multicast Join message comprises a Protocol Independent Multicast Join message.

26. The computer-readable medium of claim 23 , wherein the multicast Join message comprises a Protocol Independent Multicast Join message.