Systems and methods for convergence of network traffic after an interruption of a network device's link

1. A method comprising:

receiving, at a first network device from a second network device, a first ethernet virtual private network (EVPN) auto discovery (AD) route that comprises an ethernet segment (ES) identifier (ESI), wherein the second network device is directly connected to the ES;

receiving, at the first network device from a third network device, a second EVPN AD route that comprises the ESI, wherein the third network device is directly connected to the ES;

creating an ESI status flag indicating that a host on the ES is reachable via the second network device and the third network device;

receiving, at the first network device, a plurality of IP routes from the second network device corresponding to a plurality of multihomed hosts on the ES;

in response to determining that the ESI status flag indicates that the plurality of multihomed hosts on the ES is reachable via the second network device, generating, in a forwarding table of the first network device, an equal-cost multi-path (ECMP) construct based on the plurality of IP routes; and

in response to receiving, at the first network device from the second network device, a withdrawal of the first EVPN AD route:

updating the ESI status flag to indicate that the plurality of multihomed hosts on the ES is not reachable via the second network device; and

replacing the ECMP construct that was based on the plurality of IP routes to enable sending traffic to the plurality of multihomed hosts via the third network device, with a single next hop, without requiring separate withdrawal of advertised routes associated with the second network device.

2. The method of claim 1 , further comprising:

receiving a first data packet addressed to a MAC address of the host;

retrieving, from a forwarding entry associated with the MAC address, a next hop identifier; and

forwarding the first data packet using the next hop identifier.

3. The method of claim 1 , wherein the second network device and the third network device provide active-active multihoming to the host via the ES.

4. The method of claim 1 , wherein the withdrawal of the first EVPN AD route occurred in response to the second network device losing connection to the ES.

5. The method of claim 1 , further comprising uninstalling a plurality of routing table entries, based on the IP route received from the second network device, from hardware of the first network device.

6. The method of claim 1 , further comprising:

receiving, at the first network device from a fourth network device, a third EVPN AD route that comprises the ESI, wherein the fourth network device is directly connected to the ES;

updating the ES status flag to indicate that a host on the ES is reachable via the second network device, the third network device, and the fourth network device; and

in response to receiving, at the first network device from the second network device, a withdrawal of the first EVPN AD route, updating the ES status flag to indicate that the host on the ES is reachable via the third network device and the fourth network device.

7. The method of claim 1 , further comprising receiving, at the first network device from the second network device, a third EVPN AD route that comprises the ESI, wherein the second network device is directly connected to the ES.

8. The method of claim 7 , further comprising:

in response to receiving, at the first network device from the second network device, a third EVPN AD route that comprises the ESI, wherein the second network device is directly connected to the ES;

updating the ESI status flag to indicate that the host on the ES is reachable via the second network device and the third network device; and

updating a routing table entry that was based on the IP route to allow sending traffic to the host via the second device.

9. An apparatus comprising:

a memory configured to store a forwarding table;

communication circuitry configured to:

receive, from a first network device, a first ethernet virtual private network (EVPN) auto discovery (AD) route that comprises an ethernet segment (ES) identifier (ESI), wherein the first network device is directly connected to the ES;

receive, from a second network device, a second EVPN AD route that comprises the ESI, wherein the second network device is directly connected to the ES;

receive a plurality of IP routes from the first network device corresponding to a plurality of multihomed hosts on the ES; and

receive, from the second network device, a withdrawal of the first EVPN AD route; and

control circuitry configured to:

create an ESI status flag indicating that a host on the ES is reachable via the first network device and the second network device;

generate, in the forwarding table, an entry based on the plurality of IP routes based on determining that the ESI status flag indicates that the host on the ES is reachable via the first network device or the second network device via an equal-cost multi-path (ECMP) construct;

update the ESI status flag to indicate that the plurality of multihomed hosts on the ES is not reachable via the first network device based on the withdrawal of the first EVPN AD route; and

replace the ECMP construct that was based on the plurality of IP routes to enable sending traffic to the plurality of multihomed hosts via the second network device, with a single next hop, without requiring separate withdrawal of advertised routes associated with the first network device.

10. The apparatus of claim 9 , wherein the communication circuitry is further configured to receive a plurality of IP routes from the second network device corresponding to a plurality of hosts on the ES; and

the control circuitry is further configured to:

generate, in a forwarding table, entries based on the IP routes based on determining that the ESI status flag indicates that the plurality of hosts on the ES are reachable via the second network device; and

update the entries that were based on the IP routes to prevent sending traffic to the host via the first device.

11. The apparatus of claim 9 , wherein the communication circuitry is further configured to receive a first data packet addressed to a MAC address of the host; and

the control circuitry is further configured to retrieve, from the entry associated with the MAC address, a next hop identifier and forward the first data packet using the next hop identifier.

12. The apparatus of claim 9 , wherein the first network device and the second network device provide active-active multihoming to the host via the ES.

13. The apparatus of claim 9 , wherein the withdrawal of the first EVPN AD route occurred in response to the first network device losing connection to the ES.

14. The apparatus of claim 9 , wherein the communication circuitry is further configured to receive, from the first network device, a third EVPN AD route that comprises the ESI, wherein the first network device is directly connected to the ES.

15. The apparatus of claim 14 , wherein the control circuitry is further configured to:

update the ESI status flag to indicate that the host on the ES is reachable via the first network device and the second network device based on receiving, from the first network device, a third EVPN AD route that comprises the ESI, wherein the first network device is directly connected to the ES; and

update the entry that was based on the IP route to allow sending traffic to the host via the first device.

16. A non-transitory computer-readable medium having instructions encoded thereon that when executed by control circuitry cause the control circuitry to:

receive, from a first network device, a first ethernet virtual private network (EVPN) auto discovery (AD) route that comprises an ethernet segment (ES) identifier (ESI), wherein the first network device is directly connected to the ES;

receive, from a second network device, a second EVPN AD route that comprises the ESI, wherein the second network device is directly connected to the ES;

create an ESI status flag indicating that a host on the ES is reachable via the first network device and the second network device;

receive a plurality of IP routes from the first network device corresponding to a plurality of multihomed hosts on the ES;

generate, in a forwarding table, an entry based on the plurality of IP routes based on determining that the ESI status flag indicates that the host on the ES is reachable via the first network device or the second network device via an equal-cost multi-path (ECMP) construct;

receive, from the second network device, a withdrawal of the first EVPN AD route;

update the ESI status flag to indicate that the plurality of multihomed hosts on the ES is not reachable via the first network device based on the withdrawal of the first EVPN AD route; and

replace the ECMP construct that was based on the plurality of IP routes to enable sending traffic to the plurality of multihomed hosts via the second network device, with a single next hop, without requiring separate withdrawal of advertised routes associated with the first network device.

17. The non-transitory computer-readable medium of claim 16 , wherein the control circuitry is further configured to:

receive a plurality of IP routes from the second network device corresponding to a plurality of hosts on the ES;

generate, in a forwarding table, entries based on the IP routes based on determining that the ESI status flag indicates that the plurality of hosts on the ES are reachable via the second network device; and

update the entries that were based on the IP routes to prevent sending traffic to the host via the first device.

18. The non-transitory computer-readable medium of claim 16 , wherein the control circuitry is further configured to:

receive a first data packet addressed to a MAC address of the host;

retrieve, from the entry associated with the MAC address, a next hop identifier; and

forward the first data packet using the next hop identifier.

19. The non-transitory computer-readable medium of claim 16 , wherein the first network device and the second network device provide active-active multihoming to the host via the ES.

20. The non-transitory computer-readable medium of claim 16 , wherein the withdrawal of the first EVPN AD route occurred in response to the first network device losing connection to the ES.

21. The non-transitory computer-readable medium of claim 16 , further configured to receive, from the first network device, a third EVPN AD route that comprises the ESI, wherein the first network device is directly connected to the ES.

22. The non-transitory computer-readable medium of claim 16 , wherein the control circuitry is further configured to:

update the ESI status flag to indicate that the host on the ES is reachable via the first network device and the second network device based on receiving, from the first network device, a third EVPN AD route that comprises the ESI, wherein the first network device is directly connected to the ES; and

update the entry that was based on the IP route to allow sending traffic to the host via the first device.

23. The non-transitory computer-readable medium of claim 16 , wherein the plurality of multihomed hosts comprises a plurality of virtual machines running on a hypervisor.