Layer-3 Support in Trill Networks

1. A switch, comprising: layer-2 processing circuitry configured to determine that: outer and inner destination media access control (MAC) addresses of a packet correspond to a MAC address assigned to the switch, wherein the packet is encapsulated with an inner Ethernet header, a routable header, and an outer Ethernet header; encapsulation circuitry configured to determine that: a destination switch identifier of the routable header corresponds to a switch identifier assigned to the switch, wherein the routable header is placed between the outer and inner Ethernet headers; Internet Protocol (IP) processing circuitry configured to lookup a destination IP address of a layer-3 header of the packet in a local layer-3 forwarding table in the switch, wherein the layer-3 header is distinct from the routable header, and wherein the destination IP address is a virtual IP address assigned to a virtual IP router, which is formed based on the switch in conjunction with at least another physical switch to operate as a single router; and forwarding circuitry configured to determine an output port and construct a new header for the packet based on looking up the destination IP address in the local layer-3 forwarding table.

2. The switch of claim 1 , wherein the layer-2 processing circuitry is further configured to determine a first virtual local area network (VLAN) tag in the inner Ethernet header; and wherein the new header includes a new inner Ethernet header comprising a second VLAN tag.

3. The switch of claim 1 , wherein the switch is a member of a network of interconnected switches, wherein the network of interconnected switches is controlled as a single logical switch.

4. The switch of claim 1 , further comprising switching circuitry configured to switch the packet between VLANs based on the destination IP address.

5. The switch of claim 1 , wherein the destination switch identifier is a virtual switch identifier; and wherein the virtual IP router is associated with the virtual switch identifier.

6. The switch of claim 1 , wherein the IP processing circuitry is further configured to map the virtual IP address to a virtual media access control (MAC) address.

7. The switch of claim 1 , further comprising Address Resolution Protocol (ARP) circuitry configured to generate an ARP response for an IP address assigned to the switch, wherein the ARP response comprises a MAC address assigned to the switch.

8. A method, comprising: determining that: outer and inner destination media access control (MAC) addresses of a packet correspond to a MAC address assigned to a switch, wherein the packet is encapsulated with an inner Ethernet header, a routable header, and an outer Ethernet header; and a destination switch identifier of the routable header corresponds to a switch identifier assigned to the switch, wherein the routable header is placed between the outer and inner Ethernet headers; looking up a destination Internet Protocol (IP) address of a layer-3 header of the packet in a local layer-3 forwarding table in the switch, wherein the layer-3 header is distinct from the routable header, and wherein the destination IP address is a virtual IP address assigned to a virtual IP router, which is formed based on the switch in conjunction with at least another physical switch to operate as a single router; and determining an output port and constructing a new header for the packet based on looking up the destination IP address in the local layer-3 forwarding table.

9. The method of claim 8 , further comprising: determining a first virtual local area network (VLAN) tag in the inner Ethernet header; and including in the new header a new inner Ethernet header comprising a second VLAN tag.

10. The method of claim 8 , wherein the switch is a member of a network of interconnected switches wherein the network of interconnected switches is controlled as a single logical switch.

11. The method of claim 8 , further comprising switching the packet between VLANs based on the destination IP address.

12. The method of claim 8 , wherein the destination switch identifier is a virtual switch identifier; and wherein the virtual IP router is associated with the virtual switch identifier.

13. The method of claim 8 , further comprising mapping the virtual IP address to a virtual media access control (MAC) address.

14. The method of claim 8 , further comprising generating an Address Resolution Protocol (ARP) response for an IP address assigned to the switch, wherein the ARP response comprises a MAC address assigned to the switch.

15. A computing system, comprising: a processor; and a non-transitory computer-readable storage medium storing instructions which when executed by the processor causes the processor to perform a method, the method comprising: determining that: outer and inner destination media access control (MAC) addresses of a packet correspond to a MAC address assigned to the computing system, wherein the packet is encapsulated with an inner Ethernet header, a routable header, and an outer Ethernet header; and a destination switch identifier of the routable header corresponds to a switch identifier is assigned to the computing system; looking up a destination Internet Protocol (IP) address of a layer-3 header of the packet in a local layer-3 forwarding table in the computing system, wherein the layer-3 header is distinct from the routable header and wherein the destination IP address is a virtual IP address assigned to a virtual IP router, which is formed based on the switch in conjunction with at least another physical switch to operate as a single router; and determining an output port and constructing a new header for the packet based on looking up the destination IP address in the local-layer-3 forwarding table.

16. The computing system of claim 15 , within the method further comprises: determining a first virtual local area network (VLAN) tag in the inner Ethernet header; and including in the new header a new inner Ethernet header comprising a second VLAN tag.

17. The computing system of claim 15 , wherein the computing system is a member of a network of interconnected switches, wherein the network of interconnected switches is controlled as a single logical switch.

18. The computing system of claim 15 , wherein the destination switch identifier is a virtual switch identifier; and wherein the virtual IP router is associated with the virtual switch identifier.

19. The computing system of claim 15 , wherein the method further comprises generating an Address Resolution Protocol (ARP) response for an IP address assigned to the computing system, wherein the ARP response comprises a MAC address assigned to the computing system.

20. The computing system of claim 15 , whether the method further comprises switching the packet between VLANs based on the destination IP address.