WO2016062268A1

WO2016062268A1 - Dynamic host configuration protocol reconnection method, dhcp server and system

Info

Publication number: WO2016062268A1
Application number: PCT/CN2015/092657
Authority: WO
Inventors: 韩斌
Original assignee: 中兴通讯股份有限公司
Priority date: 2014-10-23
Filing date: 2015-10-23
Publication date: 2016-04-28
Also published as: CN105592172A

Abstract

Disclosed are a dynamic host configuration protocol (DHCP) reconnection method, DHCP server and system. The method comprises: when a terminal switches from a first DHCP server to a second DHCP server, broadcasting outward a first DHCP request message; after the second DHCP server receives the first DHCP request message, and if related device information for maintaining the terminal is determined to be absent, returning a DHCPNAK message to the terminal for instructing the terminal to start a new reconnection. The present invention reduces the time delay caused by repeated attempts of DHCPREQUEST of feedthrough device, thus enabling fast reconnection.

Description

Dynamic host configuration protocol reconnection method, DHCP server and system

Technical field

The present invention relates to the field of network communication technologies, and in particular, to a dynamic host configuration protocol reconnection method, a DHCP server, and a system.

Background technique

Dynamic Host Configuration Protocol (DHCP) is a LAN network protocol that works with UDP protocol. Based on the Client/Server working mode, it provides IP addresses and configuration parameters for hosts on the Internet. There are two main purposes: to internal The network or network service provider automatically assigns an IP address to the user or internal network administrator as a means of centrally managing all computers.

At present, it is more and more important to obtain the address through the DHCP device, and the DHCP server sends the DHCPREQUEST packet to the device. The DHCP server is based on RFC2131. The specification 4.3.2 is silent, in order to deal with multiple DHCP Servers on the same line (see Figure 1). This causes the attached device to continuously send multiple DHCPREQUESTs without receiving a response. It can only wait for the retry to end. Resend the DHCPDISCOVER packet to open a new connection process to obtain the address. As a result, the reconnecting device has a large reconnection delay. , giving the user a poor experience.

Summary of the invention

The embodiment of the present invention provides a dynamic host configuration protocol reconnection method, a DHCP server, and a system, which are designed to at least solve the problem that the access device has a large delay in obtaining an address caused by switching the DHCP server, and realize the DHCP of the attached device. Reconnection.

In order to achieve the above objectives, the embodiment of the present invention provides a dynamic host configuration protocol reconnection method, including:

When the terminal switches from the first DHCP server to the second DHCP server, the terminal broadcasts the first DHCP request message;

After receiving the first DHCP request message, the second DHCP server determines that if the related device information of the terminal is not maintained, the device returns a DHCPNAK message to the terminal to notify the terminal to start a new one. Reconnect process.

The method also includes:

After receiving the DHCPNAK message, the terminal sends a second DHCP request message to the second DHCP server, and confirms that the second DHCP server is selected;

The second DHCP server returns a DHCPACK message to the terminal.

The method also includes:

After receiving the DHCPNAK packet, the terminal broadcasts a DISCOVER packet;

After receiving the DISCOVER message, the second DHCP server returns a DHCPOFFER message to the terminal;

After receiving the DHCPOFFER message, the terminal sends a second DHCP request message to the second DHCP server, and confirms that the second DHCP server is selected;

The second DHCP server returns a DHCPACK message to the terminal.

The step of the terminal broadcasting the first DHCP request message before the step of switching from the first DHCP server to the second DHCP server further includes:

After the terminal accesses the first DHCP server, the terminal broadcasts a DISCOVER message;

After receiving the DISCOVER message, the first DHCP server returns a DHCPOFFER message to the terminal;

After receiving the DHCPOFFER message, the terminal sends a second DHCP request message to the first DHCP server, and confirms that the first DHCP server is selected;

The first DHCP server returns a DHCPACK message to the terminal.

The embodiment of the invention further provides a dynamic host configuration protocol reconnection method, including:

The DHCP server receives the first DHCP request message broadcasted by the terminal;

Determining whether the related device information of the terminal is maintained according to the first DHCP request message;

If the related device information of the terminal is not maintained, the DHCPNAK packet is returned to the terminal to notify the terminal to start a new reconnection process.

The method also includes:

Receiving a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

Returning a DHCPACK message to the terminal.

The method also includes:

Receiving a DISCOVER message broadcasted by the terminal to the outside;

Returning a DHCPOFFER message to the terminal according to the DISCOVER message;

Returning a DHCPACK message to the terminal.

The embodiment of the invention further provides a DHCP server reconnected by the dynamic host configuration protocol, including:

a receiving module, configured to receive a first DHCP request message broadcasted by the terminal;

The determining module is configured to determine, according to the first DHCP request message, whether to maintain related device information of the terminal;

The sending module is configured to: when the determining module determines that the related device information of the terminal is not maintained, return a DHCPNAK message to the terminal to notify the terminal to start a new reconnection process.

The receiving module is further configured to receive a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

The sending module is further configured to return a DHCPACK message to the terminal.

The receiving module is further configured to receive a DISCOVER packet broadcasted by the terminal.

The sending module is further configured to: return a DHCPOFFER message to the terminal according to the DISCOVER message;

The embodiment of the present invention further provides a system for reconnecting a dynamic host configuration protocol, including a first DHCP server, a second DHCP server, and a terminal that is respectively connected to the first DHCP server and the second DHCP server; wherein:

The second DHCP server is the above DHCP server;

The terminal is configured to: when the first DHCP server is switched to the second DHCP server, broadcast the first DHCP request message; and receive the DHCPNAK message returned by the second DHCP server, and according to the DHCPNAK report This article opens a new reconnection process.

A method for reconnecting a dynamic host configuration protocol, a DHCP server, and a system for a terminal (a connected device) does not appear to be connected to multiple DHCP servers at the same time, if the attached device sends a DHCPREQUEST request message. After the DHCP server determines that the related device information is not maintained, the DHCPNAK packet is directly replied to the DHCP device to immediately send the DHCPDISCOVER to start the new address acquisition process, thereby eliminating the delay caused by the DHCPREQUEST retry of the attached device. At the time, the purpose of rapid reconnection was achieved.

DRAWINGS

1 is a flow chart of interaction between DHCP according to specifications when an existing terminal switches networks;

2 is a schematic flowchart of an embodiment of a method for reconnecting a dynamic host configuration protocol according to the present invention;

3 is a schematic flowchart of another embodiment of a dynamic host configuration protocol reconnection method according to the present invention;

4 is a schematic flow chart of still another embodiment of a dynamic host configuration protocol reconnection method according to the present invention;

5 is a detailed flow chart of an embodiment of a dynamic host configuration protocol reconnection method shown in FIG. 4;

6 is a schematic flowchart of still another embodiment of a dynamic host configuration protocol reconnection method according to the present invention;

7 is a schematic flowchart of still another embodiment 2 of a dynamic host configuration protocol reconnection method according to the present invention;

FIG. 8 is a schematic flowchart diagram of still another third embodiment of a dynamic host configuration protocol reconnection method according to the present invention; FIG.

FIG. 9 is a schematic flowchart diagram of still another fourth embodiment of a dynamic host configuration protocol reconnection method according to the present invention; FIG.

10 is a schematic diagram of functional modules of an embodiment of a DHCP server reconnected by a dynamic host configuration protocol according to the present invention;

FIG. 11 is a schematic structural diagram of an embodiment of a system for reconnecting a dynamic host configuration protocol according to the present invention.

In order to make the technical solutions of the present invention clearer and clearer, the following will be further described in detail with reference to the accompanying drawings.

detailed description

The solution of the embodiment of the present invention is mainly: for a terminal (the attached device), the connection between multiple DHCP servers does not occur at the same time. If the downlink device sends a DHCPREQUEST request packet, the DHCP server determines that the related device is not maintained. The information directly replies to the DHCPNAK message, prompting the attached device to immediately send a DHCPDISCOVER, and start a new acquisition of the address process, thereby eliminating the delay caused by the repeated DHCPREQUEST retry of the attached device, and achieving the purpose of fast reconnection.

First, the implementation of the existing terminal switching DHCP server will be explained.

Referring to FIG. 1, FIG. 1 is a flow chart of interaction between DHCP according to specifications when a terminal (subsidiary device) switches networks, and the specific processing flow is as follows:

Step 1: The device A is connected to the device where the DHCP server 1 (the first DHCP server) is located.

Step 2: Device A sends a DHCPDISCOVER packet.

Step 3: DHCP Server 1 replies to the DHCPOFFER message;

Step 4: The device A sends a DHCPREQUEST packet to confirm the selection of DHCP Server1.

Step 5: DHCP Server 1 replies with a DHCPACK packet, and device A obtains an address;

Step 6: The device A is switched to the DHCP server and switched to the device where the DHCP server 2 (the second DHCP server) is located. The actual application scenario is: the mobile phone switches the WIFI hotspot, and the AC switches the AP.

Step 7: After switching the DHCP server, device A will send a DHCPREQUEST packet.

Step 8. According to the requirements of RFC2131, DHCP Server2 needs to perform silent processing here.

Step 9: After the device A continuously sends multiple DHCPREQUEST messages and fails to respond, the device waits for the retry to end and sends a DISCOVER message.

Step 10: DHCP Server 2 replies to the DHCPOFFER message;

Step 11: The device A sends a DHCPREQUEST packet to confirm the selection of DHCP Server2.

In step 12, the DHCP server 2 replies to the DHCPACK packet, and the device A receives the address.

It can be seen from the above process that the existing network switching mode of the connected device causes the downlink device to continuously send multiple DHCPREQUESTs without receiving a response, and can only wait for the retry to end, and resend the DHCPDISCOVER message to start a new connection process. In order to obtain an address, the reconnection delay of the connected device is large, and the user experience is poor.

In this embodiment, when the DHCP server is switched to the DHCP server, if the newly accessed DHCP server does not maintain the related information of the device, the DHCPNAK packet is directly replied to the device to immediately restart the reconnection process. The delay caused by multiple DHCPREQUEST retry attempts to disconnect the device to achieve the purpose of fast reconnection.

Based on the foregoing analysis, an embodiment of a dynamic host configuration protocol reconnection method according to an embodiment of the present invention is proposed.

Specifically, as shown in FIG. 2, an embodiment of the present invention provides a dynamic host configuration protocol reconnection method, including:

Step S101: When the terminal switches from the first DHCP server to the second DHCP server, the terminal broadcasts the first DHCP request message.

Step S102: After receiving the first DHCP request message, the second DHCP server determines, if the related device information of the terminal is not maintained, returns a DHCPNAK message to the terminal to notify the terminal. Start a new reconnection process.

In this embodiment, when the terminal switches from the first DHCP server to the second DHCP server, the terminal broadcasts the first DHCPREQUEST packet to notify the terminal that the terminal needs to be switched from the first DHCP server to the second DHCP server. A DHCPREQUEST packet carries the IP address currently used by the terminal.

After receiving the first DHCP request message sent by the terminal, the second DHCP server determines whether the related device information of the terminal is maintained locally, and if it is determined that the related device information of the terminal is not maintained, the second DHCP server The terminal returns a DHCPNAK message to inform the terminal to initiate a new reconnection process. That is, the second DHCP server informs the terminal through the DHCPNAK message that the current logical parameter cannot satisfy the request of the terminal, and cannot provide the corresponding service to the terminal. The terminal re-opens the process of obtaining an address.

In this way, the terminal does not need to continuously send multiple DHCPREQUEST wait responses, and does not need to wait for the retry to end, but can directly resend the DHCPDISCOVER message to open a new connection process to obtain an address, thereby eliminating the delay caused by the DHCPReQUEST retry of the terminal multiple times. Achieve the goal of rapid reconnection.

As shown in FIG. 3, another embodiment of the present invention provides a dynamic host configuration protocol reconnection method. The method according to the foregoing embodiment of FIG. 2 further includes a corresponding step of the terminal to start a new reconnection process, which specifically includes:

Step S103: After receiving the DHCPNAK message, the terminal sends a second DHCP request message to the second DHCP server to confirm selection of the second DHCP server.

Step S104: The second DHCP server returns a DHCPACK message to the terminal.

Compared with the embodiment shown in FIG. 2 above, the embodiment further includes a specific solution for the terminal to start a new reconnection process.

First, after receiving the DHCPNAK message returned by the second DHCP server, the terminal directly sends a second DHCP request message to the second DHCP server, where the second DHCP request message carries the selected second DHCP server to obtain the relevant IP address. The information that confirms the selection of the second DHCP server.

After receiving the second DHCP request message sent by the terminal, the second DHCP server returns a DHCPACK message to the terminal, where the DHCPACK message is used as an acknowledgement message, carrying the IP address, route, and subnet mask assigned to the terminal device. The DNS, lease, and other information, the terminal obtains the key information such as the IP address, route, subnet mask, DNS, and lease period required for the Internet access, and the reconnection process ends.

As shown in FIG. 4, another embodiment of the present invention provides a dynamic host configuration protocol reconnection method. Based on the embodiment shown in FIG. 2, the method further includes a corresponding step of the terminal to start a new reconnection process, and the implementation manner thereof is The terminal shown in FIG. 3 above is different in starting a new reconnection process. Specifically include:

Step S105: After receiving the DHCPNAK packet, the terminal broadcasts a DISCOVER packet.

Step S106: After receiving the DISCOVER message, the second DHCP server returns a DHCPOFFER message to the terminal.

Step S1031: After receiving the DHCPOFFER message, the terminal sends a second DHCP request message to the second DHCP server, and confirms that the second DHCP server is selected.

Step S1041: The second DHCP server returns a DHCPACK message to the terminal.

First, after receiving the DHCPNAK message returned by the second DHCP server, the terminal does not directly send the second DHCP request message to the second DHCP server, but broadcasts the DISCOVER message to the outside. The DISCOVER packet carries the device identifier of the terminal, the vendor category identifier, the host name, and a series of request information, including but not limited to subnet mask, routing, domain name, and DNS.

After receiving the DISCOVER message, the second DHCP server returns a DHCPOFFER message to the terminal, and provides the terminal with information such as an IP address, a route, a subnet mask, a DNS, a lease, and the like.

After receiving the DHCPOFFER message sent by the second DHCP server, the terminal sends a second DHCP request message to the second DHCP server, where the second DHCP request message carries information about the selected second DHCP server to obtain the relevant IP address. That is, it is confirmed that the second DHCP server is selected.

The processing flow of this embodiment is described in detail below with reference to FIG. 5:

Referring to FIG. 5, FIG. 5 is a flow chart of interaction when a terminal (subscribing device) switches a network according to the embodiment. The specific processing procedure is as follows:

Step 1: The device A (terminal) connected to the device is connected to the device where the DHCP server 1 (the first DHCP server) is located.

Step 2: Device A sends a DHCPDISCOVER packet.

Step 3: The DHCP server 1 replies to the DHCPOFFER packet; the source of the DHCPOFFER packet received by the device is determined by the device to determine whether the application scenario is consistent with the embodiment of the present invention: a connected device does not access multiple DHCP servers at the same time. . If there is only one source, the application scenario is consistent with the embodiment of the present invention; if there are multiple sources, the content is not met;

Step 8, in accordance with the specifications of RFC2131, where DHCP Server 2 is to perform silent processing; In the embodiment, the DHCP server 2 directly responds to the DHCPNAK packet, so that the connected device immediately starts a new address acquisition process, thereby saving the DHCPREQUEST retry time;

Step 9: After receiving the DHCPNAK packet, the device A sends a DISCOVER packet.

Step 10: DHCP Server 2 replies to the DHCPOFFER message;

In this embodiment, the above scenario does not occur when one terminal (the attached device) does not have multiple DHCP servers connected to each other. If the DHCP device sends a DHCPREQUEST request packet, the DHCP server determines that the related device information is not maintained. Directly replying to the DHCPNAK packet, prompting the connected device to immediately send a DHCPDISCOVER to start a new acquisition of the address process, thereby eliminating the delay caused by multiple DHCPREQUEST retry attempts of the attached device, and achieving the purpose of fast reconnection.

As shown in FIG. 6, another embodiment of the present invention provides a method for reconnecting a dynamic host configuration protocol. Based on the embodiment shown in FIG. 4, when the terminal switches from the first DHCP server to the second DHCP server, the terminal is outward. Before the step of broadcasting the first DHCP request message, the method further includes:

Step S107: After the terminal accesses the first DHCP server, the terminal broadcasts a DISCOVER message.

Step S108: After receiving the DISCOVER message, the first DHCP server returns a DHCPOFFER message to the terminal.

Step S109: After receiving the DHCPOFFER message, the terminal sends a second DHCP request message to the first DHCP server, and confirms that the first DHCP server is selected.

Step S110: The first DHCP server returns a DHCPACK message to the terminal.

Compared with the foregoing embodiment, the embodiment further includes a scheme in which the terminal accesses the first DHCP server, and the process is the same as the existing DHCP specification, and the specific process shown in FIG. 1 may be referred to, and details are not described herein again.

It should be noted that this embodiment can also be implemented in combination with the foregoing embodiment shown in FIG. 2 and FIG. 3, and details are not described herein again.

As shown in FIG. 7, another embodiment 2 of the present invention provides a dynamic host configuration protocol reconnection method, which is a DHCP service. An embodiment of the method proposed by the device side, the method comprising:

Step S201: The DHCP server receives the first DHCP request message broadcasted by the terminal.

Step S202, determining, according to the first DHCP request message, whether to maintain related device information of the terminal;

Step S203: If the related device information of the terminal is not maintained, return a DHCPNAK message to the terminal to notify the terminal to start a new reconnection process.

Specifically, in this embodiment, when the terminal switches from the first DHCP server to the second DHCP server, the terminal broadcasts the first DHCPREQUEST packet to notify the terminal that the terminal needs to switch from the first DHCP server to the second DHCP server. The first DHCPREQUEST packet carries the IP address currently used by the terminal.

As shown in FIG. 8, another embodiment 3 of the present invention provides a dynamic host configuration protocol reconnection method. Based on the foregoing embodiment shown in FIG. 7, the method further includes:

Step S204: Receive a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server.

Step S205, returning a DHCPACK message to the terminal.

Compared with the embodiment shown in FIG. 7 above, the embodiment further includes a specific solution for the terminal to start a new reconnection process.

As shown in FIG. 9, another embodiment 4 of the present invention provides a dynamic host configuration protocol reconnection method. Based on the foregoing embodiment shown in FIG. 7, the method further includes a corresponding step of the terminal to start a new reconnection process, and the implementation manner thereof is The terminal shown in FIG. 8 is different in starting a new reconnection process. Specifically, it also includes:

Step S206, receiving a DISCOVER message broadcasted by the terminal to the outside;

Step S207, returning a DHCPOFFER message to the terminal according to the DISCOVER message;

Step S208, receiving a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

Step S209, returning a DHCPACK message to the terminal.

Correspondingly, an embodiment of a DHCP server reconnected by the dynamic host configuration protocol in the embodiment of the present invention is proposed.

Specifically, as shown in FIG. 10, an embodiment of the present invention provides a DHCP server that is reconnected by a dynamic host configuration protocol, and includes: a receiving module 301, a determining module 302, and a sending module 303, where:

The receiving module 301 is configured to receive a first DHCP request message that is broadcasted by the terminal.

The determining module 302 is configured to determine, according to the first DHCP request message, whether to maintain the related device of the terminal Preparation information

The sending module 303 is configured to: when the determining module determines that the related device information of the terminal is not maintained, return a DHCPNAK message to the terminal to notify the terminal to start a new reconnection process.

Further, the receiving module 301 is further configured to receive a second DHCP request message sent by the terminal, where the second DHCP request message confirms the selection. Said DHCP server;

The sending module 303 is further configured to return a DHCPACK message to the terminal.

This embodiment further includes a specific scheme in which the terminal starts a new reconnection process.

Further, the receiving module 301 is further configured to receive the DISCOVER packet broadcasted by the terminal, as another implementation manner of the terminal re-opening the new re-connection process;

The sending module 303 is further configured to: return a DHCPOFFER message to the terminal according to the DISCOVER message;

The receiving module 301 is further configured to receive a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

In addition, as shown in FIG. 11, an embodiment of the present invention further provides a system for reconnecting a dynamic host configuration protocol, including a first DHCP server 401, a second DHCP server 402, and the first DHCP server 401, and a second The DHCP server 402 communicates with the connected terminal 403; wherein:

The second DHCP server 402 may be the DHCP server described in the foregoing embodiment;

The terminal 403 is configured to: when the first DHCP server 401 is switched to the second DHCP server 402, broadcast the first DHCP request message; and receive the DHCPNAK message returned by the second DHCP server 402, and according to The DHCPNAK message initiates a new reconnection process.

The process of re-linking the dynamic host configuration protocol is implemented by the first DHCP server 401, the second DHCP server 402, and the terminal 403. For details, refer to the foregoing embodiments, and details are not described herein.

The dynamic host configuration protocol reconnection method, the DHCP server, and the system in the embodiment of the present invention, for a terminal 403 (the attached device) does not appear to be connected to multiple DHCP servers at the same time, if the downlink device sends a DHCPREQUEST request message, the DHCP server After judging that the relevant device information is not maintained, the DHCPNAK message is directly replied, prompting the attached device to immediately send a DHCPDISCOVER, and a new process of obtaining the address is started, thereby eliminating the delay caused by multiple DHCPREQUEST retry attempts of the attached device. The purpose of fast reconnection.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the invention, and the equivalent structure or process changes made by the specification and the drawings of the present invention may be directly or indirectly applied to other related technical fields. The same is included in the scope of patent protection of the present invention.

Industrial applicability

As described above, the dynamic host configuration protocol reconnection method, the DHCP server, and the system provided by the embodiments of the present invention have the following beneficial effects: for a terminal (the attached device), there is no case where multiple DHCP servers are simultaneously connected. If the DHCP server sends a DHCPREQUEST request packet, the DHCP server determines that it does not maintain the related device information, and directly responds to the DHCPNAK packet, prompting the connected device to immediately send a DHCPDISCOVER, and then start a new address acquisition process, thereby eliminating the need to hang up. The delay caused by the DHCPREQUEST retry of the device has reached the goal of fast reconnection.

Claims

A dynamic host configuration protocol reconnection method includes:

When the terminal switches from the first DHCP server to the second DHCP server, the terminal broadcasts the first DHCP request message;

After receiving the first DHCP request message, the second DHCP server determines that if the related device information of the terminal is not maintained, the device returns a DHCPNAK message to the terminal to notify the terminal to start a new one. Reconnect process.
The method of claim 1 further comprising:

After receiving the DHCPNAK message, the terminal sends a second DHCP request message to the second DHCP server, and confirms that the second DHCP server is selected;

The second DHCP server returns a DHCPACK message to the terminal.
The method of claim 1 further comprising:

After receiving the DHCPNAK packet, the terminal broadcasts a DISCOVER packet;

After receiving the DISCOVER message, the second DHCP server returns a DHCPOFFER message to the terminal;

After receiving the DHCPOFFER message, the terminal sends a second DHCP request message to the second DHCP server, and confirms that the second DHCP server is selected;

The second DHCP server returns a DHCPACK message to the terminal.
The method of claim 1, wherein the step of the terminal broadcasting the first DHCP request message before the step of switching from the first DHCP server to the second DHCP server further comprises:

After the terminal accesses the first DHCP server, the terminal broadcasts a DISCOVER message;

After receiving the DISCOVER message, the first DHCP server returns a DHCPOFFER message to the terminal;

After receiving the DHCPOFFER message, the terminal sends a second DHCP request message to the first DHCP server, and confirms that the first DHCP server is selected;

The first DHCP server returns a DHCPACK message to the terminal.
A dynamic host configuration protocol reconnection method includes:

The DHCP server receives the first DHCP request message broadcasted by the terminal;

Determining whether the related device information of the terminal is maintained according to the first DHCP request message;

If the related device information of the terminal is not maintained, the DHCPNAK packet is returned to the terminal to notify the terminal to start a new reconnection process.
The method of claim 5, further comprising:

Receiving a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

Returning a DHCPACK message to the terminal.
The method of claim 5, further comprising:

Receiving a DISCOVER message broadcasted by the terminal to the outside;

Returning a DHCPOFFER message to the terminal according to the DISCOVER message;

Receiving a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

Returning a DHCPACK message to the terminal.
A DHCP server reconnected by a dynamic host configuration protocol, including:

a receiving module, configured to receive a first DHCP request message broadcasted by the terminal;

The determining module is configured to determine, according to the first DHCP request message, whether to maintain related device information of the terminal;

The sending module is configured to: when the determining module determines that the related device information of the terminal is not maintained, return a DHCPNAK message to the terminal to notify the terminal to start a new reconnection process.
The DHCP server according to claim 8, wherein

The receiving module is further configured to receive a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

The sending module is further configured to return a DHCPACK message to the terminal.
The DHCP server according to claim 8, wherein

The receiving module is further configured to receive a DISCOVER packet broadcasted by the terminal;

The sending module is further configured to: return a DHCPOFFER message to the terminal according to the DISCOVER message;

The receiving module is further configured to receive a second DHCP request message sent by the terminal, where the second DHCP request message confirms selection of the DHCP server;

The sending module is further configured to return a DHCPACK message to the terminal.
A dynamic host configuration protocol reconnection system includes a first DHCP server, a second DHCP server, and a terminal communicably connected to the first DHCP server and the second DHCP server; wherein:

The second DHCP server is the DHCP server according to any one of claims 8-10;

The terminal is configured to: when the first DHCP server is switched to the second DHCP server, broadcast the first DHCP request message; and receive the DHCPNAK message returned by the second DHCP server, and according to the DHCPNAK report This article opens a new reconnection process.