Designated forwarder selection for multihomed hosts in an ethernet virtual private network

1. A method comprising:

receiving an indication of updated network settings for a network at a network switch;

storing a shadow hash forwarding table at the network switch by storing a hash forwarding table in current use at a time of the indication as the shadow hash forwarding table; and

forwarding a multidestination packet to a destination in the network using the shadow hash forwarding table.

2. The method of claim 1 , further comprising:

receiving an updated hash forwarding table; and

using the shadow hash forwarding table to forward the multidestination packet until the updated hash forwarding table is converged on the network switch.

3. The method of claim 1 further comprising:

determining a hash value from a selection of header values of the multidestination packet using a hash function;

determining, using the hash value, a designated forwarding status for the network switch from a hash forwarding table; and

when the network switch is a designated forwarder for the multidestination packet according to the designated forwarding status, forwarding the multidestination packet to the destination.

4. The method of claim 3 , wherein the hash value is determined using a same hash function by each edge device connected to the destination, and wherein the hash value is an 8-bit value calculated based on a 5-tuple flow information and a VLAN for the multidestination packet.

5. The method of claim 3 , wherein the hash forwarding table provides load balancing for a network by load balancing between network switches connected to the destination.

6. The method of claim 1 , further comprising:

determining a link for the destination is down;

updating a hash forwarding table to remove the down link; and

transmitting an indication of the down link to a controller.

7. A computer program product, the computer program product comprising:

a computer-readable storage medium having computer-readable program code embodied therewith, the computer-readable program code executable by one or more computer processors to perform an operation, the operation comprising:

receiving an indication of updated network settings for a network at a network switch;

storing a shadow hash forwarding table at the network switch by storing a hash forwarding table in current use at a time of the indication as the shadow hash forwarding table; and

forwarding a multidestination packet to a destination in the network using the shadow hash forwarding table.

8. The computer program product of claim 7 , wherein the operation further comprises:

receiving an updated hash forwarding table; and

using the shadow hash forwarding table to forward the multidestination packet until the updated hash forwarding table is converged on the network switch.

9. The computer program product of claim 7 , wherein the operation further comprises:

determining a hash value from a selection of header values of the multidestination packet using a hash function;

determining, using the hash value, a designated forwarding status for the network switch from a hash forwarding table; and

when the network switch is a designated forwarder for the multidestination packet according to the designated forwarding status, forwarding the multidestination packet to the destination.

10. The computer program product of claim 9 , wherein the hash value is determined using a same hash function by each edge device connected to the destination, and wherein the hash value is an 8-bit value calculated based on a 5-tuple flow information and a VLAN for the multidestination packet.

11. The computer program product of claim 9 , wherein the hash forwarding table provides load balancing for a network by load balancing between network switches connected to the destination.

12. The computer program product of claim 7 , wherein the operation further comprises:

determining a link for the destination is down;

updating a hash forwarding table to remove the down link; and

transmitting an indication of the down link to a controller.

13. A system comprising:

a processor; and

a memory comprising instructions which, when executed on the processor, performs an operation, the operation comprising:

receiving an indication of updated network settings for a network at a network switch;

storing a shadow hash forwarding table at the network switch by storing a hash forwarding table in current use at a time of the indication as the shadow hash forwarding table; and

forwarding a multidestination packet to a destination in the network using the shadow hash forwarding table.

14. The system of claim 13 , wherein the operation further comprises:

receiving an updated hash forwarding table; and

using the shadow hash forwarding table to forward the multidestination packet until the updated hash forwarding table is converged on the network switch.

15. The system of claim 13 , wherein the operation further comprises:

determining a hash value from a selection of header values of the multidestination packet using a hash function;

determining, using the hash value, a designated forwarding status for the network switch from a hash forwarding table; and

when the network switch is a designated forwarder for the multidestination packet according to the designated forwarding status, forwarding the multidestination packet to the destination.

16. The system of claim 15 , wherein the hash value is determined using a same hash function by each edge device connected to the destination, and wherein the hash value is an 8-bit value calculated based on a 5-tuple flow information and a VLAN for the multidestination packet.

17. The system of claim 15 , wherein the hash forwarding table provides load balancing for a network by load balancing between network switches connected to the destination.