Layer three multi-homing for virtual networks

1. A method comprising:

receiving, by a virtual router of a computing device for one or more virtual networks, a first tunnel packet comprising a first outer header and a first inner packet that defines a first packet flow;

determining, based at least on the first outer header, that the first tunnel packet is associated with a first virtual network of the one or more virtual networks;

associating, based on the first inner packet, the first tunnel packet to a first layer three link of a plurality of layer three links coupling the virtual router to two or more top-of-rack switches in the first virtual network, wherein the plurality of layer three links form a layer three multi-homing connection between the virtual router and the two or more top-of-rack switches in the first virtual network; and

transmitting, based on associating the first tunnel packet to the first layer three link, the first tunnel packet via the first layer three link of the plurality of layer three links.

2. The method of claim 1 , further comprising:

receiving a second tunnel packet comprising a second outer header and a second inner packet that defines a second packet flow;

determining, based at least on the second outer header, that the second tunnel packet is associated with the first virtual network of the one or more virtual networks;

associating, based on the second inner packet, the second tunnel packet to a second layer three link of the plurality of layer three links coupling the virtual router to the two or more top-of-rack switches in the first virtual network; and

transmitting, based on associating the second tunnel packet to the second layer three link, the second tunnel packet via the second layer three link of the plurality of layer three links.

3. The method of claim 1 , wherein the layer three multi-homing connection between the virtual router and the two or more top-of-rack switches comprises an active-active multi-homing connection between the virtual router and the two or more top-of-rack switches.

4. The method of claim 1 , wherein associating the first tunnel packet to the first layer three link comprises applying a hash to an inner header of the first inner packet to associate the first tunnel packet with the first layer three link, wherein the inner header identifies the first packet flow as one or more of a source address, a destination address, a source port, a destination port, and a protocol.

5. The method of claim 1 , wherein associating the first tunnel packet to the first layer three link comprises applying a hash to both the first outer header and an inner header of the first inner packet to associate the first tunnel packet with the first layer three link, wherein the inner header identifies the first packet flow as one or more of a source address, a destination address, a source port, a destination port, and a protocol.

6. The method of claim 1 , wherein associating the first packet flow to the first layer three link comprises performing load balancing with respect to the first packet flow to associate the first packet flow with the first layer three link such that traffic loads are balanced across the plurality of layer three links.

7. The method of claim 5 , wherein performing load balancing comprises performing equal cost multi-path with respect to the first packet flow to associate the first packet flow with the first layer three link.

8. The method of claim 1 , wherein associating the first packet flow to the first layer three link comprises associating, by the virtual router, the first packet flow to the first layer three link without having a bonding drive configured to maintain the layer three multi-homing connection between the virtual router and the two or more top-of-rack switches.

9. The method of claim 1 , further comprising configuring a first tunnel that operates via the layer three multi-homing connection such that the first tunnel packet receives a label identifying the first tunnel regardless of whether the first packet flow is associated with the first layer three link or a different layer three link of the plurality of layer three links.

10. The method of claim 1 , further comprising:

receiving configuration data specifying multiple layer two links; and

configuring, based on the configuration data, the layer three multi-homing connection via the multiple layer two links.

11. A network system comprising:

a switch fabric comprising a plurality of switches interconnected to form a physical network;

a virtual network controller configured to configure and manage virtual networks within the physical network; and

a plurality of servers interconnected by the switch fabric, wherein each of the servers comprises an operating environment configured to execute one or more virtual machines in communication via the virtual networks, and wherein the servers comprise a set of virtual routers configured to extend the virtual networks to the virtual machines,

wherein a virtual router of the set of virtual routers is configured to:

receive a first tunnel packet comprising a first outer header and a first inner packet that defines a first packet flow;

determine, based at least on the first outer header, that the first tunnel packet is associated with a first virtual network of the one or more virtual networks;

associate, based on the inner packet, the first tunnel packet to a first layer three link of a plurality of layer three links coupling the virtual router to two or more top-of-rack switches in the first virtual network, wherein the plurality of layer three links form a layer three multi-homing connection between the virtual router and the two or more top-of-rack switches in the first virtual network; and

transmit the first tunnel packet via the first layer three link of the plurality of layer three links.

12. The network system of claim 11 , wherein the virtual router of the set of virtual routers is further configured to:

receive a second tunnel packet comprising a second outer header and a second inner packet that defines a second packet flow;

determine, based at least on the second outer header, that the second tunnel packet is associated with the first virtual network of the one or more virtual networks;

associate, based on the second inner packet, the second tunnel packet to a second layer three link of the plurality of layer three links coupling the virtual router to the two or more top-of-rack switches in the first virtual network; and

transmit, based on associating the second tunnel packet to the second layer three link, the second tunnel packet via the second layer three link of the plurality of layer three links.

13. The network system of claim 11 , wherein the layer three multi-homing connection between the virtual router and the two or more top-of-rack switches comprises an active-active multi-homing connection between the virtual router and the two or more top-of-rack switches.

14. The network system of claim 11 , wherein the virtual router of the set of virtual routers, to associate the first tunnel packet to the first layer three link, is configured to apply a hash to an inner header of the first inner packet to associate the first tunnel packet with the first layer three link, wherein the inner header identifies the first packet flow as one or more of a source address, a destination address, a source port, a destination port, and a protocol.

15. The network system of claim 11 , wherein the virtual router of the set of virtual routers, to associate the first tunnel packet to the first layer three link, is configured to apply a hash to both the first outer header and an inner header of the first inner packet to associate the first tunnel packet with the first layer three link, wherein the inner header identifies the first packet flow as one or more of a source address, a destination address, a source port, a destination port, and a protocol.

16. The network system of claim 11 , wherein the virtual router of the set of virtual routers, to associate the first tunnel packet to the first layer three link, is configured to perform load balancing with respect to the first packet flow to associate the first packet flow with the first layer three link such that traffic loads are balanced across the plurality of layer three links.

17. The network system of claim 15 , wherein the virtual router of the set of virtual routers, to perform load balancing, is configured to perform equal cost multi-path with respect to the first packet flow to associate the first packet flow with the first layer three link.

18. The network system of claim 11 , wherein the virtual router of the set of virtual routers, to associate the first tunnel packet to the first layer three link, is configured to associate the first packet flow to the first layer three link without having a bonding drive configured to maintain the layer three multi-homing connection between the virtual router and the two or more top-of-rack switches.

19. The network system of claim 11 , wherein the virtual router of the set of virtual routers is further configured to configure a first tunnel that operates via the layer three multi-homing connection such that the first tunnel packet receives a label identifying the first tunnel regardless of whether the first packet flow is associated with the first layer three link or a different layer three link of the plurality of layer three links.

20. A non-transitory computer-readable medium comprising instructions for causing one or more programmable processors to:

receive, by a virtual router of a computing device for one or more virtual networks, a first tunnel packet comprising a first outer header and a first inner packet that defines a first packet flow;

determine, based at least on the first outer header, that the first tunnel packet is associated with a first virtual network of the one or more virtual networks;

associate, based on the inner packet, the first packet flow to a first layer three link of a plurality of layer three links coupling the virtual router to two or more top-of-rack switches in the first virtual network, wherein the plurality of layer three links form a layer three multi-homing connection between the virtual router and the two or more top-of-rack switches in the first virtual network; and

transmit the first tunnel packet via the first layer three link of the plurality of layer three links.