Apparatus and method for preserving routable IP addresses using ARP proxy

• US 20040095943A1
• Filed: 11/15/2002
• Published: 05/20/2004
• Est. Priority Date: 11/15/2002
• Status: Active Grant

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Korotin, Dmitry O.
• Granted Patent: US 7,512,136 B2
• Time in Patent Office: Days
• US Class Current: 370/401
• CPC Class Codes: H04L 61/00 Network arrangements, protocols or services for addressing or naming
• CPC Class Codes: H04L 61/10 of different types
• CPC Class Codes: H04L 61/59 using proxies for addressing

Abstract

An Address Resolution Protocol (ARP) request is received at a gateway coupled to a first local network from a first host also coupled to the first local network. The ARP request includes a destination IP address of a second host coupled to a second local network. Also, a source IP address of the first host and the destination IP address are within the same IP address sub-network. A local network address of the gateway is then sent to the first host in reply to the ARP request, based on an entry for the destination IP address in an ARP proxy table stored on the gateway. A packet is subsequently acquired from the first host addressed to the second host. The packet'"'"'s header includes the source IP address and the destination IP address. Finally the packet is transmitted toward the second host.

Claims

1. A method for preserving Internet Protocol (IP) addresses, comprising:

receiving at a gateway coupled to a first local network an Address Resolution Protocol (ARP) request from a first host also coupled to said first local network, where said ARP request includes a destination IP address of a second host coupled to a second local network, and where a source IP address of said first host and said destination IP address are within a common IP address sub-network;

sending a local network address of said gateway to said first host in reply to said ARP request, based on an entry for said destination IP address in an ARP proxy table stored on said gateway;

acquiring at said gateway a packet from said first host, addressed to said second host, where said packet includes said source IP address and said destination IP address; and

transmitting said packet toward said second host.

2. The method of claim 1, further comprising, before said sending, determining that said destination IP address is on a common IP address sub-network to said source IP address.

3. The method of claim 1, wherein said transmitting further comprises sending said packet to a Default Gateway of said gateway based on an entry for said destination IP address in a routing table stored on said gateway.

4. The method of claim 3, wherein sending comprises transmitting said packet to the Internet.

5. The method of claim 1, wherein said transmitting further comprises sending said packet to a third host coupled to a third local network based on a entry for said destination IP address in a routing table stored on said gateway, where said gateway is also coupled to said third local network, and where said source IP address and said destination IP address are within the same IP address sub-network.

6. The method of claim 1, further comprising, before said sending, looking-up said destination IP address in said ARP proxy table.

7. The method of claim 1, further comprising, before said transmitting, looking-up said destination IP address in said routing table.

8. The method of claim 1, further comprising, before said receiving, building a routing table.

9. The method of claim 8, further comprising generating said ARP proxy table based on said routing table.

10. The method of claim 9, wherein said generating comprises:

setting up a distinct sub-table for each local network coupled to said gateway;

providing an IP address for each host coupled to each local network;

creating, for each IP address, a corresponding instruction not to send said local network address of said gateway in reply to an ARP request; and

generating, for all other IP addresses, an instruction to send said local network address of said gateway in reply to an ARP request.

11. A method for preserving Internet Protocol (IP) addresses, comprising:

receiving at a gateway coupled to a first local network an Address Resolution Protocol (ARP) request from a first host also coupled to said first local network, where said ARP request includes a destination Internet Protocol (IP) address of a second host coupled to a second local network also coupled to said gateway, and where a source IP address of said first host and said destination IP address are within the same IP address sub-network;

sending a local network address of said gateway to said first host in reply to said ARP request, based on an entry for said destination IP address in an ARP proxy table stored on said gateway;

receiving a packet from said first host addressed to said second host, where said packet includes said source IP address and said destination IP address; and

transmitting said packet toward said second local network for receipt by said second host.

12. The method of claim 11, further comprising, before said sending, looking-up said destination IP address in said ARP proxy table.

13. The method of claim 11, further comprising, before said transmitting, looking-up said destination IP address in said routing table.

14. The method of claim 11, further comprising, before said receiving, remotely updating said ARP proxy table and said routing table on said gateway whenever a new host is added to said first local network.

15. A gateway for preserving Internet Protocol (IP) addresses, comprising:

a Central Processing Unit (CPU);

communications circuitry coupled to a first local network and the Internet, where said communications circuitry has a unique local network address;

at least two ports for communicating with said first local network and the Internet;

a memory, comprising;

an operating system;

a Address Resolution Protocol (ARP) table containing a list of destination IP addresses and associated instructions for sending said local network address to a first host also coupled to said first local network, where said first host has a source IP address;

a routing table containing a list of destination IP addresses and associated instructions for routing packets to one of said ports;

communication procedures comprising;

instructions for receiving an ARP request from said first host, where said ARP request includes a destination IP address of a second host coupled to a second local network, and where said source IP address and said destination IP address are within the same IP address sub-network;

instructions for sending said local network address to said first host in reply to said ARP request, based on an entry for said destination IP address in said ARP proxy table;

instructions for acquiring a packet from said first host addressed to said second host, where said packet includes said source IP address and said destination IP address; and

instructions for transmitting said packet toward said second host.

16. The gateway of claim 15, wherein said instructions for transmitting further comprise instructions for sending said packet to a Default Gateway of said gateway based on a entry for said destination IP address in said routing table.

17. The gateway of claim 16, wherein instructions for sending further comprise instructions for transmitting said packet to the Internet.

18. The gateway of claim 15, wherein said instructions for transmitting further comprises instructions for sending said packet to a third host coupled to a third local network based on a entry for said destination IP address in said routing table, where said gateway is also coupled to said third local network, and where said source IP address and said destination IP address are within the same IP address sub-network.

19. The gateway of claim 15, wherein said memory further comprises ARP procedures for looking-up said destination IP address in said ARP proxy table.

20. The gateway of claim 15, wherein said memory further comprises routing procedures for looking-up said destination IP address in said routing table.

21. The gateway of claim 15, wherein said memory further comprises instructions for remotely updating said ARP proxy table and said routing table on said gateway whenever a new host is added to said first local network.

22. A system for preserving Internet Protocol (IP) addresses, comprising:

a first host having a source IP address and coupled to a first gateway via a first local network;

a second host having a destination IP address and coupled to a second gateway via a second local network;

the Internet coupled to both said first gateway and said second gateway, where said first gateway comprises;

a Central Processing Unit (CPU);

communications circuitry coupled to a first local network and the Internet, where said communications circuitry has a unique local network address;

at least two ports for communicating with said first local network and the Internet;

a memory, comprising;

an operating system;

a Address Resolution Protocol (ARP) table containing a list of destination IP addresses and associated instructions for sending said local network address to a first host also coupled to said first local network, where said first host has a source IP address;

a routing table containing a list of destination IP addresses and associated instructions for routing packets to one of said ports;

communication procedures comprising;

instructions for receiving an ARP request from said first host, where said ARP request includes a destination IP address of a second host coupled to a second local network, and where said source IP address and said destination IP address are within the same IP address sub-network;

instructions for sending said local network address to said first host in reply to said ARP request, based on an entry for said destination IP address in said ARP proxy table;

instructions for acquiring a packet from said first host addressed to said second host, where said packet includes said source IP address and said destination IP address; and

instructions for transmitting said packet toward said second host.

23. A computer program product for preserving Internet Protocol (IP) addresses, the computer program product comprising a computer readable storage and a computer program stored therein, the computer program comprising:

instructions for receiving at a gateway coupled to a first local network an Address Resolution Protocol (ARP) request from a first host also coupled to said first local network, where said ARP request includes a destination IP address of a second host coupled to a second local network, and where a source IP address of said first host and said destination IP address are within the same IP address sub-network;

instructions for sending a local network address of said gateway to said first host in reply to said ARP request, based on an entry for said destination IP address in an ARP proxy table stored on said gateway;

instructions for acquiring a packet from said first host addressed to said second host, where said packet includes said source IP address and said destination IP address; and

instructions for transmitting said packet toward said second host.

24. A method for preserving Internet Protocol (IP) addresses, comprising:

assigning a first IP address from an IP address sub-network to a first host coupled to a first local network;

assigning a second IP address from said IP address sub-network to a second host coupled to a second local network, where said first local network is coupled to said second local network via the Internet; and

communicating between said first and second hosts via the Internet utilizing said first and second IP addresses.

25. The method of claim 24, wherein said communicating further comprises:

receiving at a gateway coupled to said first local network an Address Resolution Protocol (ARP) request from said first host, where said ARP request includes said second IP address;

sending a local network address of said gateway to said first host in reply to said ARP request, based on an entry for said second IP address in an ARP proxy table stored on said gateway;

acquiring at said gateway a packet from said first host addressed to said second host, where said packet is addressed to said second IP address; and

transmitting said packet toward said second host.