Address resolution using multiple designated instances of a logical router

1. A non-transitory machine readable medium storing a program for operating a logical network in a network that comprises a plurality of host machines, the program comprising sets of instructions for:

defining a logical routing element (LRE) for routing data packets between different segments of the logical network, wherein each host machine operates a set of virtual machines (VMs) and a local instance of the LRE as a managed physical routing element (MPRE) for routing packets from the set of VMs locally at the host machine, the LRE comprising a plurality of logical interfaces (LIFs), each LIF for interfacing with a different segment of the logical network, wherein a particular LIF is addressable by a plurality of different LIF addresses;

assigning each LIF address of the particular LIF to a different host machine in the plurality of host machines; and

advertising the plurality of LIF addresses of the particular LIF as a plurality of next-hops to an external router for sending packets to be routed by the LRE.

2. The non-transitory machine readable medium of claim 1 , wherein at least one of the network segments comprises network nodes in a plurality of different IP subnets.

3. The non-transitory machine readable medium of claim 1 , wherein the plurality of different LIF addresses for addressing the particular LIF comprises addresses in different IP subnets.

4. The non-transitory machine readable medium of claim 1 , wherein the particular LIF is for interfacing a particular network segment, wherein the particular network segment is an overlay encapsulation network.

5. The non-transitory machine readable medium of claim 4 , wherein the overlay encapsulation network comprises a plurality of different IP subnets.

6. The non-transitory machine readable medium of claim 4 , wherein the overlay encapsulation network is VXLAN.

7. A non-transitory machine readable medium storing a program for operating a logical network in a network that comprises a plurality of host machines, the program comprising sets of instructions for:

connecting a physical router to a logical network, the logical network comprising a plurality of network segments and a logical routing element (LRE) for routing data packets between the plurality of network segments, the LRE comprising a plurality of logical interfaces (LIF), each LIF for interfacing a network segment, wherein the physical router is a network node of a particular network segment that interfaces the LRE at a particular LIF but does not operate the LRE; and

receiving, at the physical router, a plurality of different addresses for addressing the particular LIF; and

selecting one address of the received plurality of different addresses as destination for sending a data packet to the particular LIF.

8. The non-transitory machine readable medium of claim 7 , wherein selecting one address of the plurality of different addresses comprises performing an Equal Cost Multi-path Routing (ECMP) algorithm.

9. The non-transitory machine readable medium of claim 7 , wherein the logical network is implemented over a plurality of host machines, wherein each host machine is operating a local instance of the LRE as a managed physical routing element (MPRE).

10. The non-transitory machine readable medium of claim 9 , wherein the selected address corresponds to a particular host machine, wherein said routing of the data packet is performed by the MPRE in the particular host machine.

11. The non-transitory machine readable medium of claim 7 , wherein at least one of the network segments comprises network nodes in a plurality of different IP subnets.

12. The non-transitory machine readable medium of claim 7 , wherein the received plurality of addresses for addressing the particular LIF comprises addresses in different IP subnets.

13. The non-transitory machine readable medium of claim 7 , wherein particular network segment is an overlay encapsulation network.

14. A method for operating a logical network in a network that comprises a plurality of host machines, the method comprising:

defining a logical routing element (LRE) for routing data packets between different segments of the logical network, wherein each host machine operates a set of virtual machines (VMs) and a local instance of the LRE as a managed physical routing element (MPRE) for routing packets from the set of VMs locally at the host machine, the LRE comprising a plurality of logical interfaces (LIFs), each LIF for interfacing with a different segment of the logical network, wherein a particular LIF is addressable by a plurality of different LIF addresses;

assigning each LIF address of the particular LIF to a different host machine in the plurality of host machines; and

advertising the plurality of LIF addresses of the particular LIF as a plurality of next-hops to an external router for sending packets to be routed by the LRE.

15. The method of claim 14 , wherein at least one of the network segments comprises network nodes in a plurality of different IP subnets.

16. The method of claim 14 , wherein the plurality of different LIF addresses for addressing the particular LIF comprises addresses in different IP subnets.

17. The method of claim 14 , wherein the particular LIF is for interfacing a particular network segment, wherein the particular network segment is an overlay encapsulation network.

18. The method of claim 14 , wherein the overlay encapsulation network comprises a plurality of different IP subnets.

19. The method of claim 14 , wherein the overlay encapsulation network is VXLAN.