Techniques for exchanging DHCP information among DHCP relay agents and DHCP servers

• US 20080025299A1
• Filed: 07/28/2006
• Published: 01/31/2008
• Est. Priority Date: 07/28/2006
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Droms, Ralph, Johnson, Richard, Agarwal, Anand, Sukiman, Indrajanti, Tanwar, Anshul, Sundaresan, Krishna
• Granted Patent: US 7,586,912 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• 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 61/5014 using dynamic host configuration protocol [DHCP] or bootstrap protocol [BOOTP]
• CPC Class Codes: H04L 61/59 using proxies for addressing

Abstract

A technique involves exchanging DHCP relay agent information with a DHCP server. In particular, the technique involves receiving a DHCP message en route from a DHCP client to the DHCP server. The DHCP message includes (i) a non-option portion having a client identifier identifying the DHCP client and (ii) an option portion having first relay agent information added to the DHCP message by a first relay agent. The technique further involves modifying the option portion of the DHCP message to simultaneously include both the first relay agent information added by the first relay agent and second relay agent information from a second relay agent. The technique further involves sending the DHCP message with the modified option portion to the DHCP server. Accordingly, the DHCP server is capable of receiving relay agent information from multiple relay agents and assigning an address to the DHCP client based on this input.

Claims

1. In a data communications device, a method for exchanging Dynamic Host Configuration Protocol (DHCP) relay agent information with a DHCP server, the method comprising:

receiving a DHCP message en route from a DHCP client to the DHCP server, the DHCP message including (i) a non-option portion having a client identifier identifying the DHCP client and (ii) an option portion having first relay agent information added to the DHCP message by a first relay agent;

modifying the option portion of the DHCP message to simultaneously include both the first relay agent information added by the first relay agent and second relay agent information from a second relay agent; and

sending the DHCP message with the modified option portion to the DHCP server.

2. A method as in claim 1 wherein, prior to modifying the option portion, the DHCP message includes an initial Relay Agent Information Option containing the first relay agent information added by the first relay agent;

and wherein modifying the option portion of the DHCP message to simultaneously include both the first relay agent information and the second relay agent information from the second relay agent includes;

providing a new Relay Agent Information Option in place of the initial Relay Agent Information Option of the DHCP message, the new Relay Agent Information Option excluding the non-option portion of the DHCP message.

3. A method as in claim 2 wherein providing the new Relay Agent Information Option in place of the initial Relay Agent Information Option of the DHCP message includes:

containing the initial Relay Agent Information Option within a first sub-option of the new Relay Agent Information Option; and

containing the second relay agent information from the second relay agent within a second sub-option of the new Relay Agent Information Option.

4. A method as in claim 2 wherein providing the new Relay Agent Information Option in place of the initial Relay Agent Information Option of the DHCP message includes:

integrating the first relay agent information and the second relay agent information into a single sub-option of the new Relay Agent Information Option.

5. A method as in claim 1, further comprising:

obtaining, as a response to the DHCP message, another DHCP message en route from the DHCP server to the DHCP client, the other DHCP message including (i) a non-option portion having the client identifier identifying the DHCP client and (ii) an option portion that echoes the modified option portion which simultaneously includes both the first relay agent information and second relay agent information.

6. A method as in claim 5, further comprising:

changing the option portion of the other DHCP message to (i) include the first relay agent information and (ii) exclude the second relay agent information; and

outputting the other DHCP message with the changed option portion.

7. A method as in claim 6 wherein obtaining the other DHCP message includes:

receiving, as the option portion of the other DHCP message, an echoed Relay Agent Information Option having (i) the first relay agent information contained within a first sub-option of the echoed Relay Agent Information Option and (ii) the second relay agent information contained within a second sub-option of the echoed Relay Agent Information Option.

8. A method as in claim 6 obtaining the other DHCP message includes:

receiving, as the option portion of the other DHCP message, an echoed Relay Agent Information Option having the first relay agent information and the second relay agent information integrated within a single sub-option of the echoed Relay Agent Information Option.

9. A data communications device, comprising:

a receiver;

a transmitter; and

control circuitry coupled to the receiver and the transmitter, the control circuitry being configured to;

receive, through the receiver, a Dynamic Host Configuration Protocol (DHCP) message en route from a DHCP client to a DHCP server, the DHCP message including (i) a non-option portion having a client identifier identifying the DHCP client and (ii) an option portion having first relay agent information added to the DHCP message by a first relay agent;

modify the option portion of the DHCP message to simultaneously include both the first relay agent information added by the first relay agent and second relay agent information from a second relay agent; and

send, through the transmitter, the DHCP message with the modified option portion to the DHCP server.

10. A data communications device as in claim 9 wherein, prior to modification of the option portion, the DHCP message includes an initial Relay Agent Information Option containing the first relay agent information added by the first relay agent;

and wherein the control circuitry, when modifying the option portion of the DHCP message to simultaneously include both the first relay agent information and the second relay agent information from the second relay agent, is configured to;

provide a new Relay Agent Information Option in place of the initial Relay Agent Information Option of the DHCP message, the new Relay Agent Information Option excluding the non-option portion of the DHCP message.

11. A data communications device as in claim 10 wherein the control circuitry, when providing the new Relay Agent Information Option in place of the initial Relay Agent Information Option of the DHCP message, is configured to:

contain the initial Relay Agent Information Option within a first sub-option of the new Relay Agent Information Option; and

contain the second relay agent information from the second relay agent within a second sub-option of the new Relay Agent Information Option.

12. A data communications device as in claim 10 wherein the control circuitry, when providing the new Relay Agent Information Option in place of the initial Relay Agent Information Option of the DHCP message, is configured to:

integrate the first relay agent information and the second relay agent information into a single sub-option of the new Relay Agent Information Option.

13. A data communications device as in claim 9 wherein the control circuitry is further configured to:

obtain, as a response to the DHCP message, another DHCP message en route from the DHCP server to the DHCP client, the other DHCP message including (i) a non-option portion having the client identifier identifying the DHCP client and (ii) an option portion that echoes the modified option portion which simultaneously includes both the first relay agent information and second relay agent information.

14. A data communications device as in claim 13 wherein the control circuitry is further configured to:

change the option portion of the other DHCP message to (i) include the first relay agent information and (ii) exclude the second relay agent information; and

output, through the transmitter, the other DHCP message with the changed option portion.

15. A data communications device as in claim 14 wherein, the control circuitry, when obtaining the other DHCP message, is configured to:

receive, as the option portion of the other DHCP message, an echoed Relay Agent Information Option through the receiver, the echoed Relay Agent Information Option having (i) the first relay agent information contained within a first sub-option of the echoed Relay Agent Information Option and (ii) the second relay agent information contained within a second sub-option of the echoed Relay Agent Information Option.

16. A data communications device as in claim 14 wherein, the control circuitry, when obtaining the other DHCP message, is configured to:

receive, as the option portion of the other DHCP message, an echoed Relay Agent Information Option through the receiver, the echoed Relay Agent Information Option having the first relay agent information and the second relay agent information integrated within a single sub-option of the echoed Relay Agent Information Option.

17. In a Dynamic Host Configuration Protocol (DHCP) server, a method for exchanging DHCP relay agent information, the method comprising:

receiving a DHCP message from a DHCP client through multiple DHCP relay agents, the DHCP message including (i) a non-option portion having a client identifier identifying the DHCP client and (ii) an option portion having first relay agent information added to the DHCP message by a first relay agent and second relay agent information added to the DHCP message by a second relay agent;

generating another DHCP message based on both the first relay agent information and the second relay agent information; and

sending the other DHCP message to the DHCP client through the multiple DHCP relay agents.

18. A method as in claim 17 wherein the option portion of the DHCP message includes a Relay Agent Information Option containing the first relay agent information and the second relay agent information;

and wherein sending the other DHCP message includes;

outputting, as the option portion of other DHCP message, an echoing Relay Agent Information Option that echoes the Relay Agent Information Option of the DHCP message, the echoing Relay Agent Information Option having (i) the first relay agent information contained within a first sub-option of the echoing Relay Agent Information Option and (ii) the second relay agent information contained within a second sub-option of the echoing Relay Agent Information Option.

19. A method as in claim 17 wherein the option portion of the DHCP message includes a Relay Agent Information Option containing the first relay agent information and the second relay agent information;

and wherein sending the other DHCP message includes;

outputting, as the option portion of other DHCP message, an echoing Relay Agent Information Option that echoes the Relay Agent Information Option of the DHCP message, the echoing Relay Agent Information Option including the first relay agent information and the second relay agent information integrated within a single sub-option of the echoing Relay Agent Information Option.

20. A Dynamic Host Configuration Protocol (DHCP) server, comprising:

a receiver;

a transmitter; and

control circuitry coupled to the receiver and the transmitter, the control circuitry being configured to;

receive a DHCP message from a DHCP client through multiple DHCP relay agents and through the receiver, the DHCP message including (i) a non-option portion having a client identifier identifying the DHCP client and (ii) an option portion having first relay agent information added to the DHCP message by a first relay agent and second relay agent information added to the DHCP message by a second relay agent;

generate another DHCP message based on both the first relay agent information and the second relay agent information; and

send the other DHCP message to the DHCP client through the transmitter and through the multiple DHCP relay agents.

21. A DHCP server as in claim 20 wherein the option portion of the DHCP message includes a Relay Agent Information Option containing the first relay agent information and the second relay agent information;

and wherein the control circuitry, when sending the other DHCP message, is configured to;

output, as the option portion of other DHCP message, an echoing Relay Agent Information Option that echoes the Relay Agent Information Option of the DHCP message, the echoing Relay Agent Information Option having (i) the first relay agent information contained within a first sub-option of the echoing Relay Agent Information Option and (ii) the second relay agent information contained within a second sub-option of the echoing Relay Agent Information Option.

22. A DHCP server as in claim 20 wherein the option portion of the DHCP message includes a Relay Agent Information Option containing the first relay agent information and the second relay agent information;

and wherein the control circuitry, when sending the other DHCP message, is configured to;

output, as the option portion of other DHCP message, an echoing Relay Agent Information Option that echoes the Relay Agent Information Option of the DHCP message, the echoing Relay Agent Information Option including the first relay agent information and the second relay agent information integrated within a single sub-option of the echoing Relay Agent Information Option.