Method and apparatus for forwarding traffic between locally attached networks using level 3 addressing information

• US 7,222,188 B1
• Filed: 01/19/2000
• Issued: 05/22/2007
• Est. Priority Date: 12/08/1995
• Status: Expired due to Fees

• Current Assignee: RPX Corporation
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Ames, Steve, Bialkowski, Jan, Byrne, Donal, Cave, Dennis
• Primary Examiner(s): Cardone, Jason
• Assistant Examiner(s): Pollack, Melvin H.
• Application Number:
  US09/488,945
• Time in Patent Office: 2,680 Days
• Field of Search: 709/242, 709/250, 709/249, 709/238, 709/243, 709/244, 370/399, 370/389, 370/392, 370/395.1, 370/396, 370/397, 370/398, 370/395.3, 370/395.31, 370/395.32, 370/395.51, 370/395.52, 370/395.54, 370/400, 370/401
• US Class Current: 709/238
• CPC Class Codes: H04L 49/201 Multicast operation; Broadcast operation
• CPC Class Codes: H04L 49/354 for supporting virtual local area networks [VLAN]
• CPC Class Codes: H04L 49/602 Multilayer or multiprotocol switching, e.g. IP switching

Abstract

A method and apparatus for layer 3 switching packets between locally attached virtual local area networks without using a routing protocol are provided. A learning internetwork switch is connected between a router and a plurality of virtual local area networks. Communications between devices on the virtual local area networks and the router pass through the learning internetwork switch. By inspecting certain packets that flow between the devices and the router, the learning internetwork switch learns the location of the devices without having to use a routing protocol. The learning internetwork switch learns the network layer and the data link layer addresses of the various devices. Once the learning internetwork switch has learned the location, the network layer address and data link layer address of a device, the learning internetwork switch can forward packets between devices on different virtual local area networks using layer 3 switching without involving the router.

Claims

1. A switch comprising:

a plurality of ports including (i) a first plurality of ports adapted for coupling to a plurality of devices, including a source device being a member of a first network and a destination device being a member of a second network, and (ii) a second plurality of ports coupled to a router so that the switch is interposed between the router and the plurality of devices; and

a mechanism to determine, using layer three (L3) information contained in a packet received by a source port of the plurality of ports, which one of the plurality of ports is coupled to the destination device and to transfer information contained in the packet to the destination device without use of a routing function, the mechanism further generates a data structure including layer two (L2) addresses and corresponding layer three (L3) addresses associated with the destination device before transferring information to the destination device, the data structure being populated based on prior communications with the router.

2. The switch of claim 1, wherein the mechanism analyzes data transmitted between the router and the destination device.

3. The switch of claim 2, wherein the data is packetized in accordance with an Address Resolution Protocol.

4. The switch of claim 1, wherein the second plurality of ports are directly coupled to the router so that there are no interceding devices or local area networks between the switch and the router.

5. The switch of claim 1, wherein the destination device includes a server associated with the first network of being a virtual local area network of at least two virtual local area networks.

12. The switch of claim 1, wherein the source port is coupled to the first network being a virtual local area network.

13. The switch of claim 1, wherein the data structure is a table.

14. The switch of claim 13 operating transparent to the source device, the destination device and the router.

15. The switch of claim 13, wherein the second virtual local area network is different from the first virtual local area network.

16. The switch of claim 1, wherein a lack of usage of the routing function is a lack of use of a routing protocol.

6. A switch comprising:

a plurality of ports adapted for coupling together a plurality of virtual local area networks being at least three virtual local area networks, at least one of the plurality of ports is directly coupled to a router so that there are no interceding devices or local area networks between the switch and the router; and

a mechanism to (a) analyze information transferred from a source device of a first virtual local area network to a destination device of a second virtual local area network, (b) store information identifying a port coupled to the second virtual local area network, a layer two (L2) address of the destination device and a layer three (L3) address of the destination device corresponding to the L2 address, and (c) using the information to forward data between the plurality of virtual local area networks, the stored information forming a table that is populated based on prior communications with the router.

7. The switch of claim 6, wherein the information is obtained from packets configured in accordance with an Address Resolution Protocol.

8. The switch of claim 6, wherein the mechanism uses the information by (i) determining both the L2 address of the destination device and the port coupled to the second network based on the L3 address of the destination device supplied by the source device, and (ii) setting a destination of packets of the data to the L2 address of the destination device.

9. A network comprising:

a destination device of a first network;

a source device of a second network;

a router; and

a switch having a plurality of ports supporting communications to the destination device and operating transparently to the destination device, the source device and the router, the source device and the router with one of the plurality of ports directly coupled to the router so that there are no interceding devices or local area networks between the switch and the router, the switch including software to determine, using layer three (L3) information contained in a packet received by a first port coupled to the source device, which one of the plurality of ports is coupled to the destination device, to produce a table including layer two (L2) addresses and corresponding layer three (L3) addresses associated with the destination device having been learned from prior communications with the router and to transfer information contained in the packet from the source device directed to the destination device without use of a routing function.

10. The network of claim 9, wherein the first network is separate and distinct from the second network and the switch is remotely located from the router.

17. The network of claim 9, wherein a lack of usage of the routing function is a lack of use of a routing protocol.

11. For use in transferring data from a first virtual local area network (VLAN) to a second virtual local area network (VLAN) via a switch coupled to a router and interposed between the router and the first and second virtual local area networks without assistance by the router, the method comprising;

(a) receiving a data packet by the switch, the data packet originating from a source device associated with the first virtual local area network and including a layer three (L3) address of a destination device of the second virtual local area network;

(b) determining the L2 address associated with the L3 address of the destination device through access of one or more data structures within the switch and a port of the switch to which the destination device associated with the L3 address is attached, the data structure being populated based on prior communications with the router; and

(c) setting a destination address of the data packet to the L2 address,

wherein the operations (a), (b) and (c) are conducted transparent to devices involved in the inter-VLAN communications between the first VLAN and the second VLAN including the source device, the destination device and the router.

18. The method of claim 11, wherein the one or more data structures is a table.

19. The method of claim 11 further comprising sending the data packet to the destination device.

20. Directly coupled to a router without any interceding devices or any local area networks and in communication with a destination device, a switch comprising:

a plurality of ports including a first plurality of ports adapted for communication with a plurality of devices including the destination device, the first plurality of ports being associated with at least two virtual local area networks; and

a mechanism to utilize a data structure including layer two (L2) information and corresponding layer three (L3) information associated with the destination device, the data structure being populated based on prior communications with the router and accessed to determine which one of the plurality of ports is coupled to the destination device and to send information contained in the packet to the destination device with the L2 information in the packet unchanged in order to reduce traffic on the router.

21. The switch of claim 20, wherein the plurality of ports further includes a second plurality of ports coupled to the router.

22. The switch of claim 20, wherein the mechanism further analyzes data transmitted between the router and the destination device.

23. The switch of claim 22, wherein the data is packetized in accordance with an Address Resolution Protocol.

24. The switch of claim 20 being physically removed from the router.

25. The switch of claim 20, wherein the data structure is a table.

26. A method comprising:

(a) storing a layer three (L3) address and a layer two (L2) address corresponding to the L3 address in a table accessible by a switch;

(b) forwarding a packet to a destination device placed on a first virtual local area network with the packet being processed by the switch if an L3 address of the destination device of the packet matches an L3 address in the data structure; and

(c) communicating the packet to a router directly coupled to the switch with no interceding devices or local area networks between the switch and the router if the L3 address of the destination device does not match any L3 address in the table,

wherein the switch is implemented to intercept the packet directed to the router.

27. The method of claim 26, wherein the string of the L3 address and the corresponding L2 address is in a table contained in the switch.

28. The method of claim 27, wherein prior to forwarding of the packet, the method further comprises receiving the packet from a source device by the switch, the source device being placed on a second virtual local area network.

29. The method of claim 28, wherein the source device and the destination device are placed in different virtual local area networks, and the operations (a), (b) and (c) are conducted transparent to the router and the destination device.

30. The method of claim 27, wherein the operations (a), (b) and (c) are conducted transparent to the router and the destination device.