Mechanism for Enabling Layer Two Host Addresses to be Shielded from the Switches in a Network

• US 20100098073A1
• Filed: 10/22/2008
• Published: 04/22/2010
• Est. Priority Date: 10/22/2008
• Status: Active Grant

• Current Assignee: Fortinet Inc.
• Original Assignee: Fortinet Inc.
• Inventors: Mihelich, Joseph R., Tanaka, Bert H.
• Granted Patent: US 7,957,374 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: H04L 12/56 Packet switching systems
• CPC Class Codes: H04L 2101/622 Layer-2 addresses, e.g. medium access control [MAC] addresses
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 45/66 Layer 2 routing, e.g. in Ethernet based MAN's
• CPC Class Codes: H04L 45/74 Address processing for routing
• CPC Class Codes: H04L 49/25 Routing or path finding in a switch fabric
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 61/2596 Translation of addresses of the same type other than IP, e.g. translation from MAC to MAC addresses

Abstract

A mechanism is disclosed that enables layer two host addresses (e.g. a MAC addresses) to be shielded from a network. In one implementation, the mechanism updates each packet sent by the hosts into the network to indicate that the source layer two (L2) address for that packet is a shared L2 address instead of the actual L2 address of the sending host. By doing so, the mechanism exposes only the shared L2 address to the network, and shields the actual L2 addresses of the hosts from the network. The effect of this is that the switches in the network will need to store only the shared L2 address in their forwarding tables, not the actual L2 addresses of the hosts. By reducing the number of L2 addresses that need to be stored in the forwarding tables of the switches, the mechanism improves the scalability of the network.

Claims

1. A method performed by a border component situated at a border of a network of switches, comprising:

receiving, from a first host, a first packet destined for a first destination host, wherein the first host has a first L2 (layer

     2) address and a first L3 (layer

     3) address associated therewith, and wherein the first packet includes the first L2 address as a source L2 address for the first packet, and includes the first L3 address as a source L3 address for the first packet;

deriving a first updated packet from the first packet, wherein deriving the first updated packet comprises replacing the first L2 address with a substitute L2 address associated with a communication channel of the border component, thereby making the substitute L2 address the source L2 address for the first updated packet; and

sending the first updated packet to the network of switches.

2. The method of claim 1, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address is an IP (Internet Protocol) address.

3. The method of claim 1, further comprising:

receiving, from a second host, a second packet destined for a second destination host, wherein the second host has a second L2 address and a second L3 address associated therewith, and wherein the second packet includes the second L2 address as a source L2 address for the second packet, and includes the second L3 address as a source L3 address for the second packet;

deriving a second updated packet from the second packet, wherein deriving the second updated packet comprises replacing the second L2 address with the substitute L2 address, thereby making the substitute L2 address the source L2 address for the second updated packet; and

sending the second updated packet to the network of switches.

4. The method of claim 3, further comprising:

receiving, from the network of switches, a third packet, wherein the third packet includes the first L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

accessing a data structure, wherein the data structure comprises a first set of information that indicates an association between the first L3 address and the first L2 address;

determining, based at least partially upon the first L3 address in the third packet and the first set of information, that the destination L2 address for the third packet should be the first L2 address;

deriving a third updated packet from the third packet, wherein deriving the third updated packet comprises replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the third updated packet; and

sending the third updated packet to the first host.

5. The method of claim 4, further comprising:

receiving, from the network of switches, a fourth packet, wherein the fourth packet includes the second L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

accessing the data structure, wherein the data structure comprises a second set of information that indicates an association between the second L3 address and the second L2 address;

determining, based at least partially upon the second L3 address in the fourth packet and the second set of information, that the destination L2 address for the fourth packet should be the second L2 address;

deriving a fourth updated packet from the fourth packet, wherein deriving the fourth updated packet comprises replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the fourth updated packet; and

sending the fourth updated packet to the second host.

6. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager, wherein the communication manager comprises;

means for receiving, from a first host coupled to the communication channel, a first packet destined for a first destination host, wherein the first host has a first L2 (layer

     2) address and a first L3 (layer

     3) address associated therewith, and wherein the first packet includes the first L2 address as a source L2 address for the first packet, and includes the first L3 address as a source L3 address for the first packet;

means for deriving a first updated packet from the first packet, wherein the means for deriving the first updated packet comprises means for replacing the first L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the first updated packet; and

means for sending, via the communication channel, the first updated packet to the network of switches.

7. The border component of claim 6, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address is an IP (Internet Protocol) address.

8. The border component of claim 6, wherein the communication manager further comprises:

means for receiving, from a second host coupled to the communication channel, a second packet destined for a second destination host, wherein the second host has a second L2 address and a second L3 address associated therewith, and wherein the second packet includes the second L2 address as a source L2 address for the second packet, and includes the second L3 address as a source L3 address for the second packet;

means for deriving a second updated packet from the second packet, wherein the means for deriving the second updated packet comprises means for replacing the second L2 address with the substitute L2 address, thereby making the substitute L2 address the source L2 address for the second updated packet; and

means for sending, via the communication channel, the second updated packet to the network of switches.

9. The border component of claim 8, wherein the communication manager further comprises:

means for receiving, from the network of switches via the communication channel, a third packet, wherein the third packet includes the first L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

means for accessing a data structure, wherein the data structure comprises a first set of information that indicates an association between the first L3 address and the first L2 address;

means for determining, based at least partially upon the first L3 address in the third packet and the first set of information, that the destination L2 address for the third packet should be the first L2 address;

means for deriving a third updated packet from the third packet, wherein the means for deriving the third updated packet comprises means for replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the third updated packet; and

means for sending, via the communication channel, the third updated packet to the first host.

10. The border component of claim 9, wherein the communication manager further comprises:

means for receiving, from the network of switches via the communication channel, a fourth packet, wherein the fourth packet includes the second L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

means for accessing the data structure, wherein the data structure comprises a second set of information that indicates an association between the second L3 address and the second L2 address;

means for determining, based at least partially upon the second L3 address in the fourth packet and the second set of information, that the destination L2 address for the fourth packet should be the second L2 address;

means for deriving a fourth updated packet from the fourth packet, wherein the means for deriving the fourth updated packet comprises means for replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the fourth updated packet; and

means for sending, via the communication channel, the fourth updated packet to the second host.

11. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager configured to;

receive, from a first host coupled to the communication channel, a first packet destined for a first destination host, wherein the first host has a first L2 (layer

     2) address and a first L3 (layer

     3) address associated therewith, and wherein the first packet includes the first L2 address as a source L2 address for the first packet, and includes the first L3 address as a source L3 address for the first packet;

derive a first updated packet from the first packet, wherein deriving the first updated packet comprises replacing the first L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the first updated packet; and

send, via the communication channel, the first updated packet to the network of switches.

12. The border component of claim 11, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address is an IP (Internet Protocol) address.

13. The border component of claim 11, wherein the communication manager is further configured to:

receive, from a second host coupled to the communication channel, a second packet destined for a second destination host, wherein the second host has a second L2 address and a second L3 address associated therewith, and wherein the second packet includes the second L2 address as a source L2 address for the second packet, and includes the second L3 address as a source L3 address for the second packet;

derive a second updated packet from the second packet, wherein deriving the second updated packet comprises replacing the second L2 address with the substitute L2 address, thereby making the substitute L2 address the source L2 address for the second updated packet; and

send, via the communication channel, the second updated packet to the network of switches.

14. The border component of claim 13, wherein the communication manager is further configured to:

receive, from the network of switches via the communication channel, a third packet, wherein the third packet includes the first L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

access a data structure, wherein the data structure comprises a first set of information that indicates an association between the first L3 address and the first L2 address;

determine, based at least partially upon the first L3 address in the third packet and the first set of information, that the destination L2 address for the third packet should be the first L2 address;

derive a third updated packet from the third packet, wherein deriving the third updated packet comprises replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the third updated packet; and

send, via the communication channel, the third updated packet to the first host.

15. The border component of claim 14, wherein the communication manager is further configured to:

receive, from the network of switches via the communication channel, a fourth packet, wherein the fourth packet includes the second L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

access the data structure, wherein the data structure comprises a second set of information that indicates an association between the second L3 address and the second L2 address;

determine, based at least partially upon the second L3 address in the fourth packet and the second set of information, that the destination L2 address for the fourth packet should be the second L2 address;

derive a fourth updated packet from the fourth packet, wherein deriving the fourth updated packet comprises replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the fourth updated packet; and

send, via the communication channel, the fourth updated packet to the second host.

16. A method performed by a border component situated at a border of a network of switches, comprising:

receiving, from the network of switches, a first packet intended for a first host coupled to the border component, wherein the first host has a first L2 (layer

     2) address and a first L3 (layer

     3) address associated therewith, and wherein the first packet includes the first L3 address as a destination L3 address, and includes a substitute L2 address as a destination L2 address, wherein the substitute L2 address is associated with a communication channel of the border component;

accessing a data structure, wherein the data structure comprises a first set of information that indicates an association between the first L3 address and the first L2 address;

determining, based at least partially upon the first L3 address in the first packet and the first set of information, that the destination L2 address for the first packet should be the first L2 address;

deriving a first updated packet from the first packet, wherein deriving the first updated packet comprises replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the first updated packet; and

sending the first updated packet to the first host.

17. The method of claim 16, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address is an IP (Internet Protocol) address.

18. The method of claim 16, further comprising:

receiving, from the network of switches, a second packet intended for a second host coupled to the border component, wherein the second host has a second L2 address and a second L3 address associated therewith, and wherein the second packet includes the second L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

accessing the data structure, wherein the data structure further comprises a second set of information that indicates an association between the second L3 address and the second L2 address;

determining, based at least partially upon the second L3 address in the second packet and the second set of information, that the destination L2 address for the second packet should be the second L2 address;

deriving a second updated packet from the second packet, wherein deriving the second updated packet comprises replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the second updated packet; and

sending the second updated packet to the second host.

19. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager, wherein the communication manager comprises;

means for receiving, from the network of switches via the communication channel, a first packet intended for a first host coupled to the communication channel, wherein the first host has a first L2 (layer

     2) address and a first L3 (layer

     3) address associated therewith, and wherein the first packet includes the first L3 address as a destination L3 address, and includes a substitute L2 address as a destination L2 address, wherein the substitute L2 address is associated with the communication channel;

means for accessing a data structure, wherein the data structure comprises a first set of information that indicates an association between the first L3 address and the first L2 address;

means for determining, based at least partially upon the first L3 address in the first packet and the first set of information, that the destination L2 address for the first packet should be the first L2 address;

means for deriving a first updated packet from the first packet, wherein the means for deriving the first updated packet comprises means for replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the first updated packet; and

means for sending, via the communication channel, the first updated packet to the first host.

20. The border component of claim 19, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address is an IP (Internet Protocol) address.

21. The border component of claim 19, wherein the communication manager further comprises:

means for receiving, from the network of switches via the communication channel, a second packet intended for a second host coupled to the communication channel, wherein the second host has a second L2 address and a second L3 address associated therewith, and wherein the second packet includes the second L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

means for accessing the data structure, wherein the data structure further comprises a second set of information that indicates an association between the second L3 address and the second L2 address;

means for determining, based at least partially upon the second L3 address in the second packet and the second set of information, that the destination L2 address for the second packet should be the second L2 address;

means for deriving a second updated packet from the second packet, wherein the means for deriving the second updated packet comprises means for replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the second updated packet; and

means for sending, via the communication channel, the second updated packet to the second host.

22. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager configured to;

receive, from the network of switches via the communication channel, a first packet intended for a first host coupled to the communication channel, wherein the first host has a first L2 (layer

     2) address and a first L3 (layer

     3) address associated therewith, and wherein the first packet includes the first L3 address as a destination L3 address, and includes a substitute L2 address as a destination L2 address, wherein the substitute L2 address is associated with the communication channel;

access a data structure, wherein the data structure comprises a first set of information that indicates an association between the first L3 address and the first L2 address;

determine, based at least partially upon the first L3 address in the first packet and the first set of information, that the destination L2 address for the first packet should be the first L2 address;

derive a first updated packet from the first packet, wherein deriving the first updated packet comprises replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the first updated packet; and

send, via the communication channel, the first updated packet to the first host.

23. The border component of claim 22, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address is an IP (Internet Protocol) address.

24. The border component of claim 22, wherein the communication manager is further configured to:

receive, from the network of switches via the communication channel, a second packet intended for a second host coupled to the communication channel, wherein the second host has a second L2 address and a second L3 address associated therewith, and wherein the second packet includes the second L3 address as a destination L3 address, and includes the substitute L2 address as a destination L2 address;

access the data structure, wherein the data structure further comprises a second set of information that indicates an association between the second L3 address and the second L2 address;

determine, based at least partially upon the second L3 address in the second packet and the second set of information, that the destination L2 address for second first packet should be the second L2 address;

derive a second updated packet from the second packet, wherein deriving the second updated packet comprises replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the second updated packet; and

send, via the communication channel, the second updated packet to the second host.

25. A system comprising:

a first border component comprising a first communication channel and a first communication manager, wherein the first border component is situated at a border of a network of switches and coupled to the network of switches via the first communication channel, wherein the first border component is also coupled to a first host via the first communication channel, and wherein the first communication channel has a particular L2 (layer

     2) address associated therewith; and

a second border component comprising a second communication channel and a second communication manager, wherein the second border component is also situated at a border of the network of switches and coupled to the network of switches via the second communication channel, wherein the second border component is also coupled to a second host via the second communication channel, and wherein the second communication channel has a certain L2 address associated therewith;

wherein the first communication manager is configured to;

receive, from the first host via the first communication channel, a first packet destined for the second host, wherein the first host has a first L3 (layer

     3) address and a first L2 address associated therewith, wherein the second host has a second L3 address and a second L2 address associated therewith, and wherein the first packet includes the first L3 address as a source L3 address, includes the first L2 address as a source L2 address, includes the second L3 address as a destination L3 address, and includes the certain L2 address associated with the second communication channel of the second border component as a destination L2 address;

derive a first updated packet from the first packet, wherein deriving the first updated packet comprises replacing the first L2 address with the particular L2 address associated with the first communication channel of the first border component, thereby making the particular L2 address the source L2 address for the first updated packet; and

send, via the first communication channel, the first updated packet to the network of switches to be switched to the second border component; and

wherein the second communication manager is configured to;

receive, from the network of switches via the second communication channel, the first updated packet;

access a certain data structure, wherein the certain data structure comprises a first set of information that indicates an association between the second L3 address and the second L2 address;

determine, based at least partially upon the second L3 address in the first updated packet and the first set of information, that the destination L2 address for the first updated packet should be the second L2 address;

derive a second updated packet from the first updated packet, wherein deriving the second updated packet comprises replacing the certain L2 address associated with the second communication channel of the second border component with the second L2 address, thereby making the second L2 address the destination L2 address for the second updated packet; and

send, via the second communication channel, the second updated packet to the second host.

26. The system of claim 25,

wherein the second communication manager is further configured to:

receive, from the second host via the second communication channel, a second packet destined for the first host, wherein the second packet includes the second L3 address as a source L3 address, includes the second L2 address as a source L2 address, includes the first L3 address as a destination L3 address, and includes the particular L2 address associated with the first communication channel of the first border component as a destination L2 address;

derive a third updated packet from the second packet, wherein deriving the third updated packet comprises replacing the second L2 address with the certain L2 address associated with the second communication channel of the second border component, thereby making the certain L2 address the source L2 address for the third updated packet; and

send, via the second communication channel, the third updated packet to the network of switches to be switched to the first border component; and

wherein the first communication manager is configured to;

receive, from the network of switches via the first communication channel, the third updated packet;

access a particular data structure, wherein the particular data structure comprises a second set of information that indicates an association between the first L3 address and the first L2 address;

determine, based at least partially upon the first L3 address in the third updated packet and the second set of information, that the destination L2 address for the third updated packet should be the first L2 address;

derive a fourth updated packet from the third updated packet, wherein deriving the fourth updated packet comprises replacing the particular L2 address associated with the first communication channel of the first border component with the first L2 address, thereby making the first L2 address the destination L2 address for the fourth updated packet; and

send, via the first communication channel, the fourth updated packet to the first host.

27. The system of claim 26, wherein the first L2 address, the second L2 address, the particular L2 address, and the certain L2 address are MAC (media access control) addresses, and wherein the first L3 address and the second L3 address are IP (Internet Protocol) addresses.

28. A method performed by a border component situated at a border of a network of switches, comprising:

receiving, from a first host, a first request packet requesting a L2 (layer

     2) address for a first target host, wherein the first host has a first L2 address and a first L3 (layer

     3) address associated therewith, wherein the first target host has a first target L3 address associated therewith, and wherein the first request packet includes the first L2 address as a source L2 address, includes the first L3 address as a sending L3 address, includes the first target L3 address as a target L3 address, and includes an indication that the first request packet is to be broadcasted;

obtaining the first L2 address and the first L3 address associated with the first host from the first request packet;

updating a data structure to include a first set of information indicating an association between the first L3 address and the first L2 address;

deriving a first updated request packet from the first request packet, wherein deriving the first updated request packet comprises replacing the first L2 address with a substitute L2 address associated with a communication channel of the border component, thereby making the substitute L2 address the source L2 address for the first updated request packet; and

sending the first updated request packet to the network of switches to be broadcasted throughout the network of switches.

29. The method of claim 28, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

30. The method of claim 28, further comprising:

receiving, from a second host, a second request packet requesting a L2 address for a second target host, wherein the second host has a second L2 address and a second L3 address associated therewith, wherein the second target host has a second target L3 address associated therewith, and wherein the second request packet includes the second L2 address as a source L2 address, includes the second L3 address as a sending L3 address, includes the second target L3 address as a target L3 address, and includes an indication that the second request packet is to be broadcasted;

obtaining the second L2 address and the second L3 address associated with the second host from the second request packet;

updating the data structure to include a second set of information indicating an association between the second L3 address and the second L2 address;

deriving a second updated request packet from the second request packet, wherein deriving the second updated request packet comprises replacing the second L2 address with the substitute L2 address associated with the communication channel of the border component, thereby making the substitute L2 address the source L2 address for the second updated request packet; and

sending the second updated request packet to the network of switches to be broadcasted throughout the network of switches.

31. The method of claim 30, further comprising:

receiving, from the network of switches, a first reply packet which is a reply to the first updated request packet, wherein the first reply packet includes the first L3 address, includes the substitute L2 address as a destination L2 address, includes the first target L3 address, and includes a first requested L2 address for the first target host;

accessing the data structure;

determining, based at least partially upon the first L3 address in the first reply packet and the first set of information in the data structure, that the destination L2 address for the first reply packet should be the first L2 address;

deriving a first updated reply packet from the first reply packet, wherein deriving the first updated reply packet comprises replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the first updated reply packet; and

sending the first updated reply packet to the first host.

32. The method of claim 31, wherein the first requested L2 address included in the first reply packet for the first target host is not the target host'"'"'s real L2 address but rather is an L2 address associated with a communication channel of another border component to which the first target host is coupled.

33. The method of claim 31, further comprising:

receiving, from the network of switches, a second reply packet which is a reply to the second updated request packet, wherein the second reply packet includes the second L3 address, includes the substitute L2 address as a destination L2 address, includes the second target L3 address, and includes a second requested L2 address for the second target host;

accessing the data structure;

determining, based at least partially upon the second L3 address in the second reply packet and the second set of information in the data structure, that the destination L2 address for the second reply packet should be the second L2 address;

deriving a second updated reply packet from the second reply packet, wherein deriving the second updated reply packet comprises replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the second updated reply packet; and

sending the second updated reply packet to the second host.

34. The method of claim 28, wherein the first request packet includes an indication that the first request packet is a standard address request packet, and wherein deriving the first updated request packet further comprises:

including in the first updated request packet an indication that the first updated request packet is a non-standard address request packet.

35. The method of claim 34, further comprising:

receiving, from the first host, a second request packet requesting a L2 address for the first target host, wherein the second request packet includes the first L2 address as a source L2 address, includes the first L3 address as a sending L3 address, includes the first target L3 address as a target L3 address, includes an indication that the second request packet is a standard address request packet, and includes an indication that the second request packet is to be broadcasted;

determining that the second request packet is a second request from the first host for a L2 address for the first target host, thereby determining that the first host has not received a reply to the first updated request packet;

in response to a determination that the first host has not received a reply to the first updated request packet, deriving a second updated request packet from the second request packet, wherein deriving the second updated request packet comprises replacing the first L2 address with the substitute L2 address associated with the communication channel of the border component, thereby making the substitute L2 address the source L2 address for the second updated request packet, and wherein deriving the second updated request packet does not comprise including an indication in the second updated request packet that the second updated packet is a non-standard address request packet; and

sending the second updated request packet to the network of switches to be broadcasted throughout the network of switches.

36. The method of claim 31, wherein the first request packet includes an indication that the first request packet is a standard address request packet, and wherein deriving the first updated request packet further comprises:

including in the first updated request packet an indication that the first updated request packet is a non-standard address request packet.

37. The method of claim 36, wherein the first reply packet includes an indication that the first reply packet is a non-standard address reply packet, and wherein deriving the first updated reply packet further comprises:

including in the first updated reply packet an indication that the first updated reply packet is a standard address reply packet.

38. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager, wherein the communication manager comprises;

means for receiving, from a first host coupled to the communication channel, a first request packet requesting a L2 (layer

     2) address for a first target host, wherein the first host has a first L2 address and a first L3 (layer

     3) address associated therewith, wherein the first target host has a first target L3 address associated therewith, and wherein the first request packet includes the first L2 address as a source L2 address, includes the first L3 address as a sending L3 address, includes the first target L3 address as a target L3 address, and includes an indication that the first request packet is to be broadcasted;

means for obtaining the first L2 address and the first L3 address associated with the first host from the first request packet;

means for updating a data structure to include a first set of information indicating an association between the first L3 address and the first L2 address;

means for deriving a first updated request packet from the first request packet, wherein the means for deriving the first updated request packet comprises means for replacing the first L2 address with a substitute L2 address associated with a communication channel of the border component, thereby making the substitute L2 address the source L2 address for the first updated request packet; and

means for sending, via the communication channel, the first updated request packet to the network of switches to be broadcasted throughout the network of switches.

39. The border component of claim 38, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

40. The border component of claim 38, wherein the communication manager further comprises:

means for receiving, from a second host coupled to the communication channel, a second request packet requesting a L2 address for a second target host, wherein the second host has a second L2 address and a second L3 address associated therewith, wherein the second target host has a second target L3 address associated therewith, and wherein the second request packet includes the second L2 address as a source L2 address, includes the second L3 address as a sending L3 address, includes the second target L3 address as a target L3 address, and includes an indication that the second request packet is to be broadcasted;

means for obtaining the second L2 address and the second L3 address associated with the second host from the second request packet;

means for updating the data structure to include a second set of information indicating an association between the second L3 address and the second L2 address;

means for deriving a second updated request packet from the second request packet, wherein the means for deriving the second updated request packet comprises means for replacing the second L2 address with the substitute L2 address associated with the communication channel of the border component, thereby making the substitute L2 address the source L2 address for the second updated request packet; and

means for sending, via the communication channel, the second updated request packet to the network of switches to be broadcasted throughout the network of switches.

41. The border component of claim 40, wherein the communication manager further comprises:

means for receiving, from the network of switches via the communication channel, a first reply packet which is a reply to the first updated request packet, wherein the first reply packet includes the first L3 address, includes the substitute L2 address as a destination L2 address, includes the first target L3 address, and includes a first requested L2 address for the first target host;

means for accessing the data structure;

means for determining, based at least partially upon the first L3 address in the first reply packet and the first set of information in the data structure, that the destination L2 address for the first reply packet should be the first L2 address;

means for deriving a first updated reply packet from the first reply packet, wherein the means for deriving the first updated reply packet comprises means for replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the first updated reply packet; and

means for sending, via the communication channel, the first updated reply packet to the first host.

42. The border component of claim 41, wherein the first requested L2 address included in the first reply packet for the first target host is not the target host'"'"'s real L2 address but rather is an L2 address associated with a communication channel of another border component to which the first target host is coupled.

43. The border component of claim 41, wherein the communication manager further comprises:

means for receiving, from the network of switches via the communication channel, a second reply packet which is a reply to the second updated request packet, wherein the second reply packet includes the second L3 address, includes the substitute L2 address as a destination L2 address, includes the second target L3 address, and includes a second requested L2 address for the second target host;

means for accessing the data structure;

means for determining, based at least partially upon the second L3 address in the second reply packet and the second set of information in the data structure, that the destination L2 address for the second reply packet should be the second L2 address;

means for deriving a second updated reply packet from the second reply packet, wherein the means for deriving the second updated reply packet comprises means for replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the second updated reply packet; and

means for sending, via the communication channel, the second updated reply packet to the second host.

44. The border component of claim 38, wherein the first request packet includes an indication that the first request packet is a standard address request packet, and wherein the means for deriving the first updated request packet further comprises:

means for including in the first updated request packet an indication that the first updated request packet is a non-standard address request packet.

45. The border component of claim 44, wherein the communication manager further comprises:

means for receiving, from the first host via the communication channel, a second request packet requesting a L2 address for the first target host, wherein the second request packet includes the first L2 address as a source L2 address, includes the first L3 address as a sending L3 address, includes the first target L3 address as a target L3 address, includes an indication that the second request packet is a standard address request packet, and includes an indication that the second request packet is to be broadcasted;

means for determining that the second request packet is a second request from the first host for a L2 address for the first target host, thereby determining that the first host has not received a reply to the first updated request packet;

means for deriving, in response to a determination that the first host has not received a reply to the first updated request packet, a second updated request packet from the second request packet, wherein the means for deriving the second updated request packet comprises means for replacing the first L2 address with the substitute L2 address associated with the communication channel of the border component, thereby making the substitute L2 address the source L2 address for the second updated request packet, and wherein the means for deriving the second updated request packet does not comprise means for including an indication in the second updated request packet that the second updated packet is a non-standard address request packet; and

means for sending, via the communication channel, the second updated request packet to the network of switches to be broadcasted throughout the network of switches.

46. The border component of claim 41, wherein the first request packet includes an indication that the first request packet is a standard address request packet, and wherein the means for deriving the first updated request packet further comprises:

means for including in the first updated request packet an indication that the first updated request packet is a non-standard address request packet.

47. The border component of claim 46, wherein the first reply packet includes an indication that the first reply packet is a non-standard address reply packet, and wherein the means for deriving the first updated reply packet further comprises:

means for including in the first updated reply packet an indication that the first updated reply packet is a standard address reply packet.

48. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager configured to;

receive, from a first host coupled to the communication channel, a first request packet requesting a L2 (layer

     2) address for a first target host, wherein the first host has a first L2 address and a first L3 (layer

     3) address associated therewith, wherein the first target host has a first target L3 address associated therewith, and wherein the first request packet includes the first L2 address as a source L2 address, includes the first L3 address as a sending L3 address, includes the first target L3 address as a target L3 address, and includes an indication that the first request packet is to be broadcasted;

obtain the first L2 address and the first L3 address associated with the first host from the first request packet;

update a data structure to include a first set of information indicating an association between the first L3 address and the first L2 address;

derive a first updated request packet from the first request packet, wherein deriving the first updated request packet comprises replacing the first L2 address with a substitute L2 address associated with a communication channel of the border component, thereby making the substitute L2 address the source L2 address for the first updated request packet; and

send, via the communication channel, the first updated request packet to the network of switches to be broadcasted throughout the network of switches.

49. The border component of claim 48, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

50. The border component of claim 48, wherein the communication manager is further configured to:

receive, from a second host coupled to the communication channel, a second request packet requesting a L2 address for a second target host, wherein the second host has a second L2 address and a second L3 address associated therewith, wherein the second target host has a second target L3 address associated therewith, and wherein the second request packet includes the second L2 address as a source L2 address, includes the second L3 address as a sending L3 address, includes the second target L3 address as a target L3 address, and includes an indication that the second request packet is to be broadcasted;

obtain the second L2 address and the second L3 address associated with the second host from the second request packet;

update the data structure to include a second set of information indicating an association between the second L3 address and the second L2 address;

derive a second updated request packet from the second request packet, wherein deriving the second updated request packet comprises replacing the second L2 address with the substitute L2 address associated with the communication channel of the border component, thereby making the substitute L2 address the source L2 address for the second updated request packet; and

send, via the communication channel, the second updated request packet to the network of switches to be broadcasted throughout the network of switches.

51. The border component of claim 50, wherein the communication manger is further configured to:

receive, from the network of switches via the communication channel, a first reply packet which is a reply to the first updated request packet, wherein the first reply packet includes the first L3 address, includes the substitute L2 address as a destination L2 address, includes the first target L3 address, and includes a first requested L2 address for the first target host;

access the data structure;

determine, based at least partially upon the first L3 address in the first reply packet and the first set of information in the data structure, that the destination L2 address for the first reply packet should be the first L2 address;

derive a first updated reply packet from the first reply packet, wherein deriving the first updated reply packet comprises replacing the substitute L2 address with the first L2 address, thereby making the first L2 address the destination L2 address for the first updated reply packet; and

send, via the communication channel, the first updated reply packet to the first host.

52. The border component of claim 51, wherein the first requested L2 address included in the first reply packet for the first target host is not the target host'"'"'s real L2 address but rather is an L2 address associated with a communication channel of another border component to which the first target host is coupled.

53. The border component of claim 51, wherein the communication manager is further configured to:

receive, from the network of switches via the communication channel, a second reply packet which is a reply to the second updated request packet, wherein the second reply packet includes the second L3 address, includes the substitute L2 address as a destination L2 address, includes the second target L3 address, and includes a second requested L2 address for the second target host;

access the data structure;

determine, based at least partially upon the second L3 address in the second reply packet and the second set of information in the data structure, that the destination L2 address for the second reply packet should be the second L2 address;

derive a second updated reply packet from the second reply packet, wherein deriving the second updated reply packet comprises replacing the substitute L2 address with the second L2 address, thereby making the second L2 address the destination L2 address for the second updated reply packet; and

send, via the communication channel, the second updated reply packet to the second host.

54. The border component of claim 48, wherein the first request packet includes an indication that the first request packet is a standard address request packet, and wherein deriving the first updated request packet further comprises:

including in the first updated request packet an indication that the first updated request packet is a non-standard address request packet.

55. The border component of claim 54, wherein the communication manager is further configured to:

receive, from the first host coupled to the communication channel, a second request packet requesting a L2 address for the first target host, wherein the second request packet includes the first L2 address as a source L2 address, includes the first L3 address as a sending L3 address, includes the first target L3 address as a target L3 address, includes an indication that the second request packet is a standard address request packet, and includes an indication that the second request packet is to be broadcasted;

determine that the second request packet is a second request from the first host for a L2 address for the first target host, thereby determining that the first host has not received a reply to the first updated request packet;

derive, in response to a determination that the first host has not received a reply to the first updated request packet, a second updated request packet from the second request packet, wherein deriving the second updated request packet comprises replacing the first L2 address with the substitute L2 address associated with the communication channel of the border component, thereby making the substitute L2 address the source L2 address for the second updated request packet, and wherein deriving the second updated request packet does not comprise including an indication in the second updated request packet that the second updated packet is a non-standard address request packet; and

send, via the communication channel, the second updated request packet to the network of switches to be broadcasted throughout the network of switches.

56. The border component of claim 51, wherein the first request packet includes an indication that the first request packet is a standard address request packet, and wherein deriving the first updated request packet further comprises:

including in the first updated request packet an indication that the first updated request packet is a non-standard address request packet.

57. The border component of claim 56, wherein the first reply packet includes an indication that the first reply packet is a non-standard address reply packet, and wherein deriving the first updated reply packet further comprises:

including in the first updated reply packet an indication that the first updated reply packet is a standard address reply packet.

58. A method performed by a border component situated at a border of a network of switches, comprising:

receiving, from the network of switches via a communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested, includes an indication as to whether the request packet is a standard or non-standard address request packet, and includes an indication that the request packet is to be broadcasted;

determining whether the request packet is a standard address request packet;

in response to a determination that the request packet is a standard address request packet;

broadcasting the request packet to all hosts coupled to the communication channel;

receiving a first reply packet from the target host, wherein the target host has a target host L2 address associated therewith, and wherein the first reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

deriving a first updated reply packet from the first reply packet, wherein deriving the first updated reply packet comprises replacing the target host L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the first updated reply packet; and

sending the first updated reply packet to the network of switches via the communication channel.

59. The method of claim 58, wherein the first L2 address, the target host L2 address, and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

60. The method of claim 58, further comprising:

obtaining from the first reply packet the first target L3 address and the target host L2 address; and

updating a data structure to include a set of information indicating an association between the first target L3 address and the target host L2 address.

61. The method of claim 58, wherein the first reply packet includes an indication that the first reply packet is a standard address reply packet, and wherein deriving the first updated reply packet further comprises:

including an indication in the first updated reply packet that the first updated reply packet is a non-standard address reply packet.

62. The method of claim 58, further comprising:

in response to a determination that the request packet is a non-standard address request packet;

determining whether the target host is a host that is coupled to the communication channel;

in response to a determination that the target host is a host that is coupled to the communication channel, deriving a second reply packet from the request packet, wherein deriving the second reply packet comprises replacing the first L2 address with the substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the second reply packet, inserting the substitute L2 address into the second reply packet to represent the requested L2 address for the target host, and making the first L2 address the destination L2 address for the second reply packet; and

sending the second reply packet to the network of switches via the communication channel.

63. The method of claim 62, wherein determining whether the target host is a host that is coupled to the communication channel comprises:

accessing a data structure; and

determining whether the data structure includes a set of information that includes the first target L3 address of the target host.

64. The method of claim 62, wherein deriving the second reply packet further comprises:

including an indication in the second reply packet that the second reply packet is a non-standard address reply packet.

65. The method of claim 58, further comprising:

in response to a determination that the request packet is a non-standard address request packet;

determining whether the target host is a host that is coupled to the communication channel; and

in response to a determination that the target host is not a host that is coupled to the communication channel, dropping the request packet.

66. The method of claim 58, further comprising:

in response to a determination that the request packet is a non-standard address request packet;

determining whether the target host is a host that is coupled to the communication channel;

in response to a determination that the target host is a host that is coupled to the communication channel, deriving an updated request packet from the request packet, wherein deriving the updated request packet comprises including an indication in the updated request packet that the updated request packet is a standard address request packet;

sending the updated request packet to the target host;

receiving a second reply packet from the target host, wherein the second reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

deriving a second updated reply packet from the second reply packet, wherein deriving the second updated reply packet comprises replacing the target host L2 address with the substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the second updated reply packet; and

sending the second updated reply packet to the network of switches via the communication channel.

67. The method of claim 66, wherein the second reply packet includes an indication that the second reply packet is a standard address reply packet, and wherein deriving the second updated reply packet further comprises:

including an indication in the second updated reply packet that the second updated reply packet is a non-standard address reply packet.

68. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager, wherein the communication manager comprises;

means for receiving, from the network of switches via the communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested, includes an indication as to whether the request packet is a standard or non-standard address request packet, and includes an indication that the request packet is to be broadcasted;

means for determining whether the request packet is a standard address request packet;

means for broadcasting, in response to a determination that the request packet is a standard address request packet, the request packet to all hosts coupled to the communication channel;

means for receiving, via the communication channel, a first reply packet from the target host, wherein the target host has a target host L2 address associated therewith, and wherein the first reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

deriving a first updated reply packet from the first reply packet, wherein the means for deriving the first updated reply packet comprises means for replacing the target host L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the first updated reply packet; and

means for sending the first updated reply packet to the network of switches via the communication channel.

69. The border component of claim 68, wherein the first L2 address, the target host L2 address, and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

70. The border component of claim 68, wherein the communication manager further comprises:

means for obtaining from the first reply packet the first target L3 address and the target host L2 address; and

means for updating a data structure to include a set of information indicating an association between the first target L3 address and the target host L2 address.

71. The border component of claim 68, wherein the first reply packet includes an indication that the first reply packet is a standard address reply packet, and wherein the means for deriving the first updated reply packet further comprises:

means for including an indication in the first updated reply packet that the first updated reply packet is a non-standard address reply packet.

72. The border component of claim 68, wherein the communication manager further comprises:

means for determining, in response to a determination that the request packet is a non-standard address request packet, whether the target host is a host that is coupled to the communication channel;

means for deriving, in response to a determination that the target host is a host that is coupled to the communication channel, a second reply packet from the request packet, wherein the means for deriving the second reply packet comprises means for replacing the first L2 address with the substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the second reply packet, means for inserting the substitute L2 address into the second reply packet to represent the requested L2 address for the target host, and means for making the first L2 address the destination L2 address for the second reply packet; and

means for sending the second reply packet to the network of switches via the communication channel.

73. The border component of claim 72, wherein the means for determining whether the target host is a host that is coupled to the communication channel comprises:

means for accessing a data structure; and

means for determining whether the data structure includes a set of information that includes the first target L3 address of the target host.

74. The border component of claim 72, wherein the means for deriving the second reply packet further comprises:

means for including an indication in the second reply packet that the second reply packet is a non-standard address reply packet.

75. The border component of claim 68, wherein the communication manager further comprises:

means for determining, in response to a determination that the request packet is a non-standard address request packet, whether the target host is a host that is coupled to the communication channel; and

means for dropping the request packet, in response to a determination that the target host is not a host that is coupled to the communication channel.

76. The border component of claim 68, wherein the communication manager further comprises:

means for determining, in response to a determination that the request packet is a non-standard address request packet, whether the target host is a host that is coupled to the communication channel;

means for deriving, in response to a determination that the target host is a host that is coupled to the communication channel, an updated request packet from the request packet, wherein the means for deriving the updated request packet comprises means for including an indication in the updated request packet that the updated request packet is a standard address request packet;

means for sending the updated request packet to the target host;

means for receiving a second reply packet from the target host, wherein the second reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

means for deriving a second updated reply packet from the second reply packet, wherein the means for deriving the second updated reply packet comprises means for replacing the target host L2 address with the substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the second updated reply packet; and

means for sending the second updated reply packet to the network of switches via the communication channel.

77. The border component of claim 76, wherein the second reply packet includes an indication that the second reply packet is a standard address reply packet, and wherein the means for deriving the second updated reply packet further comprises:

means for including an indication in the second updated reply packet that the second updated reply packet is a non-standard address reply packet.

78. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager configured to;

receive, from the network of switches via the communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested, includes an indication as to whether the request packet is a standard or non-standard address request packet, and includes an indication that the request packet is to be broadcasted;

determine whether the request packet is a standard address request packet;

in response to a determination that the request packet is a standard address request packet;

broadcast the request packet to all hosts coupled to the communication channel;

receive a first reply packet from the target host, wherein the target host has a target host L2 address associated therewith, and wherein the first reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

derive a first updated reply packet from the first reply packet, wherein deriving the first updated reply packet comprises replacing the target host L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the first updated reply packet; and

send the first updated reply packet to the network of switches via the communication channel.

79. The border component of claim 78, wherein the first L2 address, the target host L2 address, and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

80. The border component of claim 78, wherein the communication manager is further configured to:

obtain from the first reply packet the first target L3 address and the target host L2 address; and

update a data structure to include a set of information indicating an association between the first target L3 address and the target host L2 address.

81. The border component of claim 78, wherein the first reply packet includes an indication that the first reply packet is a standard address reply packet, and wherein deriving the first updated reply packet further comprises:

including an indication in the first updated reply packet that the first updated reply packet is a non-standard address reply packet.

82. The border component of claim 78, wherein the communication manager is further configured to:

in response to a determination that the request packet is a non-standard address request packet;

determine whether the target host is a host that is coupled to the communication channel;

in response to a determination that the target host is a host that is coupled to the communication channel, derive a second reply packet from the request packet, wherein deriving the second reply packet comprises replacing the first L2 address with the substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the second reply packet, inserting the substitute L2 address into the second reply packet to represent the requested L2 address for the target host, and making the first L2 address the destination L2 address for the second reply packet; and

send the second reply packet to the network of switches via the communication channel.

83. The border component of claim 82, wherein determining whether the target host is a host that is coupled to the communication channel comprises:

accessing a data structure; and

determining whether the data structure includes a set of information that includes the first target L3 address of the target host.

84. The border component of claim 82, wherein deriving the second reply packet further comprises:

including an indication in the second reply packet that the second reply packet is a non-standard address reply packet.

85. The border component of claim 78, wherein the communication manager is further configured to:

in response to a determination that the request packet is a non-standard address request packet;

determine whether the target host is a host that is coupled to the communication channel; and

in response to a determination that the target host is not a host that is coupled to the communication channel, drop the request packet.

86. The border component of claim 78, wherein the communication manager is further configured to:

in response to a determination that the request packet is a non-standard address request packet;

determine whether the target host is a host that is coupled to the communication channel;

in response to a determination that the target host is a host that is coupled to the communication channel, derive an updated request packet from the request packet, wherein deriving the updated request packet comprises including an indication in the updated request packet that the updated request packet is a standard address request packet;

send the updated request packet to the target host;

receive a second reply packet from the target host, wherein the second reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

derive a second updated reply packet from the second reply packet, wherein deriving the second updated reply packet comprises replacing the target host L2 address with the substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the second updated reply packet; and

send the second updated reply packet to the network of switches via the communication channel.

87. The border component of claim 86, wherein the second reply packet includes an indication that the second reply packet is a standard address reply packet, and wherein deriving the second updated reply packet further comprises:

including an indication in the second updated reply packet that the second updated reply packet is a non-standard address reply packet.

88. A method performed by a border component situated at a border of a network of switches, comprising:

receiving, from the network of switches via a communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, and includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested;

determining whether the target host is a host that is coupled to the communication channel;

in response to a determination that the target host is a host that is coupled to the communication channel, deriving a reply packet from the request packet, wherein deriving the reply packet comprises replacing the first L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the reply packet, inserting the substitute L2 address into the reply packet to represent the requested L2 address for the target host, and making the first L2 address the destination L2 address for the reply packet; and

sending the reply packet to the network of switches via the communication channel.

89. The method of claim 88, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

90. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager, wherein the communication manager comprises;

means for receiving, from the network of switches via the communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, and includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested;

means for determining whether the target host is a host that is coupled to the communication channel;

means for deriving, in response to a determination that the target host is a host that is coupled to the communication channel, a reply packet from the request packet, wherein the means for deriving the reply packet comprises means for replacing the first L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the reply packet, means for inserting the substitute L2 address into the reply packet to represent the requested L2 address for the target host, and means for making the first L2 address the destination L2 address for the reply packet; and

means for sending the reply packet to the network of switches via the communication channel.

91. The border component of claim 90, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

92. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager configured to;

receive, from the network of switches via the communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, and includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested;

determine whether the target host is a host that is coupled to the communication channel;

in response to a determination that the target host is a host that is coupled to the communication channel, derive a reply packet from the request packet, wherein deriving the reply packet comprises replacing the first L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the source L2 address for the reply packet, inserting the substitute L2 address into the reply packet to represent the requested L2 address for the target host, and making the first L2 address the destination L2 address for the reply packet; and

send the reply packet to the network of switches via the communication channel.

93. The border component of claim 92, wherein the first L2 address and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

94. A method performed by a border component situated at a border of a network of switches, comprising:

receiving, from the network of switches via a communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, and includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested;

determining whether the target host is a host that is coupled to the communication channel;

in response to a determination that the target host is a host that is coupled to the communication channel, sending the request packet, or an updated version thereof, to the target host;

receiving a reply packet from the target host, wherein the target host has a target host L2 address associated therewith, and wherein the reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

deriving an updated reply packet from the reply packet, wherein deriving the updated reply packet comprises replacing the target host L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the updated reply packet; and

sending the updated reply packet to the network of switches via the communication channel.

95. The method of claim 94, wherein the first L2 address, the target host L2 address, and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

96. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager, wherein the communication manager comprises;

means for receiving, from the network of switches via the communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, and includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested;

means for determining whether the target host is a host that is coupled to the communication channel;

means for sending, in response to a determination that the target host is a host that is coupled to the communication channel, the request packet, or an updated version thereof, to the target host;

means for receiving a reply packet from the target host, wherein the target host has a target host L2 address associated therewith, and wherein the reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

means for deriving an updated reply packet from the reply packet, wherein the means for deriving the updated reply packet comprises means for replacing the target host L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the updated reply packet; and

means for sending the updated reply packet to the network of switches via the communication channel.

97. The border component of claim 96, wherein the first L2 address, the target host L2 address, and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.

98. A border component situated at a border of a network of switches, comprising:

a communication channel; and

a communication manager configured to;

receive, from the network of switches via the communication channel, a request packet requesting a L2 (layer

     2) address for a target host, wherein the target host has a first target L3 (layer

     3) address associated therewith, and wherein the request packet includes a first L2 address as a source L2 address, includes a first L3 address as a sending L3 address, and includes the first target L3 address as the L3 address for the target host for which a requested L2 address is being requested;

determine whether the target host is a host that is coupled to the communication channel;

send, in response to a determination that the target host is a host that is coupled to the communication channel, the request packet, or an updated version thereof, to the target host;

receive a reply packet from the target host, wherein the target host has a target host L2 address associated therewith, and wherein the reply packet includes the first L3 address, includes the first L2 address as a destination address, includes the first target L3 address, includes the target host L2 address as the requested L2 address for the target host, and includes the target host L2 address as a source L2 address;

derive an updated reply packet from the reply packet, wherein deriving the updated reply packet comprises replacing the target host L2 address with a substitute L2 address associated with the communication channel, thereby making the substitute L2 address the requested L2 address for the target host, and making the substitute L2 address the source L2 address for the updated reply packet; and

send the updated reply packet to the network of switches via the communication channel.

99. The border component of claim 98, wherein the first L2 address, the target host L2 address, and the substitute L2 address are MAC (media access control) addresses, and wherein the first L3 address and the first target L3 address are IP (Internet Protocol) addresses.