CN103179227B - The method of the Selection of chiller in IPv6 network and switching address configuration mode - Google Patents

Abstract

A method for selecting and switching address configuration modes by a host in an IPv6 network, first adding C and S two flags of standard and identification host selection and switching address configuration modes in the RA message of the ND protocol, and then performing the following operations: The router sets the two flag bits C and S and other fields. The router periodically sends RA messages to hosts on the IPv6 link, or sends RA messages to the IPv6 link after the router receives an RS request. After receiving the RA message, the host parses the C and S flags and records them in the status bits. The host decides to use the SLAAC mechanism or the DHCPv6 protocol to configure the IPv6 address according to the selection specification of the host address configuration mode set by the C and S flag bits; The specified address configuration method. The invention can meet the requirements of hosts to coordinate and use two address configuration modes to configure IPv6 addresses, and can also meet the requirements of network address management and network renumbering.

Description

Method for Host Selection and Switching Address Configuration Mode in IPv6 Network

technical field

The invention relates to a method for selecting and switching an address configuration mode of a host in an IPv6 network, and belongs to the technical field of network communication.

Background technique

Different from the automatic acquisition of IPv4 addresses, hosts in IPv6 networks automatically obtain IPv6 addresses in the following two ways: IPv6 Dynamic Host Configuration Protocol DHCPv6 (Dynamic Host Configuration Protocol for IPv6) and stateless address automatic configuration mechanism SLAAC (Stateless Address Auto-configuration). Therefore, when the host wants to automatically obtain an address, there are two options for automatic address configuration. In this way, there is the problem of selection and cooperation between the above two address configuration methods. The host must determine how to coordinate the use of these two methods to configure its IPv6 address: use the SLAAC mechanism to configure the address, or use the DHCPv6 protocol to obtain the address, or both. ? Although in the prior art, the automatic configuration flag bit A (Autonomousflag) and the management flag bit M (Managed flag) in the router advertisement RA (RouterAdvertisements) message of the neighbor discovery protocol ND (NeighborDiscovery) can respectively indicate whether the host computer configures the SLAAC address or whether Use the DHCPv6 protocol to obtain an IPv6 address, but there are obvious defects in these two flags.

The DHCP protocol is a protocol based on the client/server model. The DHCP protocol can provide addresses and other network parameter information to network devices, and is divided into two versions, v4 and v6. DHCPv6 can transfer network configuration parameters including IPv6 network addresses to IPv6 nodes through a DHCPv6 server. In contrast to IPv6 stateless address configuration SLAAC, DHCPv6 is stateful; because the DHCPv6 server maintains detailed information about each client. In order to obtain an IPv6 address, the client computer first sends requests to all DHCP servers in the network, and once it gets a reply from a certain DHCP server, it applies to the server for assigning network addresses and other network configuration information. Referring to FIG. 1 , this figure shows the above-mentioned working process for a host to obtain an address through the DHCPv6 protocol.

The host can also automatically obtain an IPv6 address through the stateless address autoconfiguration SLAAC mechanism. SLAAC generates an IPv6 address through the RA message of the ND protocol, and the RA message is broadcast by the router to the hosts in the subnet. Its characteristic is that the host does not need to be manually configured, and the router only needs a small amount of configuration, and no additional server is required. The SLAAC mechanism allows the host to combine its own information with the information advertised by the router to generate a global address, and then the global address can be used after uniqueness verification. That is, SLAAC completes the automatic configuration of the host address through the following two steps:

Step 1: Generate a global address using a stateless autoconfiguration process.

Step 2: Perform a conflict detection process on the same link to determine the uniqueness of the address.

Referring to Figure 2, the specific generation process of the global address is introduced: the router announces the prefix identifying the subnet through the RA message, the host receives the RA message, and obtains the prefix of the subnet it is in, and the host also passes the MAC (MediumAccessControl ) identifier and the EUI-64 specification generate a unique interface identifier by itself, and then combine the two to generate a global address. In addition, in the standard defining the SLAAC mechanism, the life cycle that the IPv6 address should follow is also described. The IPv6 address bound to each interface has a corresponding lifetime. When the lifetime expires, the bound address will become invalid, and then the address will be assigned to other interfaces in the network.

In order to better deal with the invalidation process of IPv6 addresses, the IPv6 addresses allocated to network interfaces will go through two different stages, and the introduction of IPv6 life cycle will better maintain the continuity of network communication.

See Figure 3, which introduces the two stages that IPv6 addresses go through in the IPv6 life cycle:

(1) Preferred period: At first, an address is "preferred", that is, its use in any session is not restricted. New sessions (such as opening a new TCP connection) should use preferred addresses whenever possible.

(2) Deprecated period: After the set time, the IPv6 address will become "expired" (deprecated), indicating that the address is about to expire. Using an address while it is in the expiration phase is discouraged, but not strictly prohibited. Only some old session connections will continue to use the "expired" Deprecated address in order to prevent service interruption.

Now introduce the prior art relevant to the present invention:

The two fields of the M flag and the A flag in the prefix information option in the RA message respectively affect whether the host uses the DHCPv6 protocol to obtain an address and whether to use the SLAAC mechanism to configure the address.

The standard [RFC2642] defines the SLAAC mechanism, and also defines two flag bits M and A each occupying 1 bit space in the RA message format (see Figure 4(A)).

The purpose of the M flag bit (ManagedFlag) in the RA message recently received from the host is to identify whether the host receiving the RA message uses the DHCPv6 protocol to configure an IPv6 address. In the RA message received by the host, when the M flag changes from 0 to 1 (false to true), if the host does not use the DHCPv6 protocol to configure the address, a DHCPv6 session will be initiated; if the M flag changes from 1 to 0, The host has no action. And the M flag is 0 by default. It should be pointed out that the M flag field in the prior art is not a mandatory standard, and does not require the host to implement it, but is a suggestion for the host.

When configuring the SLAAC address, the RA message carries prefix information in the optional item, and the A flag is a flag bit (accounting for 1 bit) in the prefix information optional item, and its purpose is to identify whether the prefix information is applied to the SLAAC mechanism: if If the A flag is set to false, the host will ignore this option; if the A flag is true, the host will use the prefix information to configure an IPv6 address.

The set M flag and A flag can meet the requirements of the host to obtain the IPv6 address through the SLAAC mechanism or the DHCPv6 protocol to a certain extent. Referring to Figure 5, taking a simple subnet with two address configuration modes as an example, it introduces how the network administrator configures the RA message as follows to select the configuration mode of the host address:

(1) When the host in the subnet only wants to obtain an IPv6 address through the SLAAC mechanism, the flag bits in the RA message are set: M=0 and A=1.

(2) When the host computer in the subnet only wants to obtain the IPv6 address through the DHCPv6 protocol, the flag bits in the RA message are set: M=1 and A=0, or the RA message is set not to carry the optional prefix information.

(3) When the host in the subnet wishes to obtain an IPv6 address through the SLAAC mechanism and the DHCPv6 protocol, the relevant flag bits in the RA message are set: M=1 and A=1.

Although the existing technology can meet the management requirements of the host address configuration mode in some scenarios, it has the following defects:

(A) The role of the M flag is too simple to meet the cooperation requirements of SLAAC and DHCPv6. The basic requirements of the cooperation mechanism between SLAAC and DHCPv6 are: the hosts must coordinate the use of the two address configuration modes and ensure normal communication between the hosts. Because when the two address configuration methods are used at the same time, the host may use the SLAAC mechanism to configure the address or the DHCPv6 protocol to configure the address, or use the two address configuration methods at the same time. Although the subnet shown in Figure 5 can meet this requirement, if there are two routers and two kinds of RA messages in the subnet, the IPv6 address configuration result will become chaotic and unpredictable, and it cannot meet the host configuration requirements. The address is on demand.

(B) When the host address configuration result is unpredictable, the network side cannot control the host to perform SLAAC-to-DHCPv6 conversion and other related operations.

(C) Because the M flag only plays a suggestive role for the operating system. Therefore, when the operating system is implemented, the host can follow the function described by the M flag bit, or ignore it, and even change the original meaning of the M field. This leads to different situations for hosts with different operating system platforms, so that different hosts in the same network may have different address configuration results, thereby affecting network management.

(D) The existing technology cannot meet the requirements of network renumbering: in addition to the requirement of converting from SLAAC to DHCPv6, it cannot meet the following requirements: when hosts perform renumbering, they hope to abandon it as soon as possible while following the IPv6 life cycle The old prefix, that is, the IPv6 address with the old prefix finishes its life cycle as soon as possible, and neither the M flag nor the A flag can provide this function.

(E) There are few definitions of host address behavior. For example, there is no description of how the host configures the address when it fails to receive the RA message, and whether it needs to initiate a DHCPv6 session.

Contents of the invention

In view of this, the purpose of the present invention is to provide a method for controlling the host to select and switch between the SLAAC/DHCPv6 address configuration methods for the defects of the prior art solutions, so as to meet the requirements of configuring the IPv6 address for the host on the network side. The need for management and network renumbering meets the requirements of the host to obtain an IPv6 address on demand in the scenario where the two address configuration modes coexist. There is evidence to follow.

In order to achieve the above object, the present invention provides a method for host selection and switching address configuration mode in an IPv6 network, characterized in that: the method is: at first the router announcement RA (RouterAdvertisements) message of the ND (NeighborDiscovery) protocol is found in the neighbor Two new flags are added to standardize and identify the host selection and switching address configuration mode: C flag (ControlFlag), that is, the "address configuration control command" field and S flag (SingleFlag), that is, the "single configuration mode command " field; where:

The S flag indicates that the host only uses one address configuration method, that is, the stateless address automatic configuration mechanism SLAAC (StatelessAddressAuto-configuration) is used alone, or the IPv6 dynamic host configuration protocol DHCPv6 (DynamicHostConfigurationProtocolforIPv6) is used alone;

The C flag indicates that the RA message has control over the address configuration operation of the host, that is, the host must strictly follow the definitions and instructions of the relevant flags, namely the M, A, C, and S flags;

Then perform the following steps:

(1) The router configures the newly added C flag and S flag of the RA message and other fields of the RA message;

(2) The router sends RA messages to the host computer on the IPv6 link regularly, or after the router receives the router request RS (RouterSolicitation), it sends the RA message to the IPv6 link;

(3) After the host receives the RA message, it analyzes the C and S flags in the RA message, and records them in the status bits;

(4) The host decides to use the SLAAC mechanism or the DHCPv6 protocol to configure its IPv6 address according to the selection specification of the host address configuration mode set by the C and S flags; The selection specification of the host address configuration mode set by the C and S flag bits, switch to the address configuration mode set by the M and A flag bits; in this step, the host executes the address configuration mode according to the analyzed C and S flag bits Actions include the following different cases:

(4A) If C=0, S=0, the host follows the suggested description of the M flag bit in the standard [RFC2462] and the description of the A flag bit in the standard [RFC4862]: when C=0, S=0, the new None of the additional flags play a role, so follow the original definition of the M and A flags;

(4B) If C=0, S=1, because C=0 indicates that the RA message does not have the control right of address configuration, and S=1 indicates that the host should use an address configuration method for address configuration;

If M=1, it means that the host only uses the DHCPv6 protocol to configure the address, then the host should initiate a DHCPv6 session or maintain a DHCPv6 address, and does not configure the SLAAC address with the prefix in the RA message;

If M=0 and A=1, it means that the host only uses the SLAAC mechanism to configure the address, that is, configure the SLAAC address with the prefix of the RA message, and when the DHCPv6 address expires, it will not renew the contract with the DHCPv6 server;

(4C) If C=1, the host configures the address according to the following specifications: C, M, S, and A flag bits can control the host to use DHCPv6, SLAAC, and DHCPv6 and SLAAC to configure the address respectively, and realize different address configuration methods Switching to meet the requirements of host address configuration and network renumbering.

The two flag bit fields of C and S each occupy 1 bit space, and are sequentially set in the reserved field on the right side of the existing M and O fields in the RA message, and correspond to "address configuration control command" and "single configuration mode command".

The step (4C) includes the following different address configuration methods:

(4C1) If M=0 and S=0, the address configuration behavior of the host is not defined or regulated, and the RA message is only an announcement message carrying a network prefix;

(4C2) If M=1, S=0, and A=1, the host must use two address configuration methods to configure the IPv6 address, that is, the host uses the RA message to configure the SLAAC address, and at the same time initiates a DHCPv6 session or continues to maintain the DHCPv6 address;

(4C3) If M=0, S=1, and A=1, the host only uses the SLAAC mechanism to configure the address; if the host has already configured a DHCPv6 address at this time, the survival time of the DHCPv6 address life cycle should be set to the minimum hour length, so that The DHCPv6 address is expired as early as possible; meanwhile, the host ignores the DHCPv6 configuration of the host by ignoring other RA messages of flag bit C=0;

(4C4) If M=1, S=1, the host only uses the DHCPv6 protocol to configure the address; if the host has configured the SLAAC address at this time, the survival time of the SLAAC address life cycle should be set to the minimum hour length, so that the SLAAC address can be used as soon as possible. Expired; at the same time, the host ignores the SLAAC configuration performed on the host by other RA messages with the flag bit C=0.

The minimum hour length of the address life cycle in the steps (4C3) and (4C4) is set to 2 hours, if the survival time of the address is greater than 2 hours, then modify the survival time of the address to 2 hours at this time; if the If the lifetime of the address is less than 2 hours, it will not be modified.

The basis of the method is based on the RA message sent by the router in the ND protocol. If the host does not receive the RA message when obtaining the address, the host should initiate a DHCPv6 session at this time, trying to use the DHCPv6 protocol to configure the address to ensure that the host is as successful as possible. Get the address.

The innovative technology of the method for selecting and switching the address configuration mode of the IPv6 host of the present invention is: first, the RA message of the ND protocol is expanded, that is, a new command field is added to define the specification of the host selection and switching address configuration mode, so that the host can be based on The instruction of the router RA message determines which address automatic configuration method to choose to obtain the IPv6 address, thereby realizing the control of the host address configuration on the network side.

The advantages and effects of the present invention are: a new SLAAC and DHCPv6 cooperation mechanism is proposed, which can meet the requirements of hosts to coordinate and use two address configuration methods to configure IPv6 addresses, so that the behavior specifications of hosts are clear and clear, and no longer have vague definitions and operation.

The present invention adds new flag bits on the basis of the standard RA message format without affecting the original flag bits. Although the present invention defines a new flag bit for the RA message format, if the newly defined flag bit is not set, there is no difference from the original definition of the RA message, so it has good compatibility.

The present invention can clearly define the host address configuration behavior in a network where two address configuration modes coexist, so that the behavior of the host configuration address mode has a clear operating standard, which can meet the requirements of network address management and network renumbering, It also enables network administrators to control the address configuration mode of hosts in the network by setting relevant flag bits, realizes switching between SLAAC and DHCPv6 addresses, shortens the lifetime of unused addresses, and facilitates renumbering. Furthermore, the method of the present invention follows the life cycle of the IPv6 address when switching between SLAAC and DHCPv6, and can better maintain network communication. Therefore, the present invention has very good application prospects.

Description of drawings

FIG. 1 is a flow chart of assigning network addresses by the DHCPv6 protocol.

Fig. 2 is a schematic diagram of the generation process of the global IPv6 address in the SLAAC mechanism.

FIG. 3 is a schematic diagram of an IPv6 address life cycle.

4(A) and (B) are schematic diagrams of RA message format and new RA message format defined in the present invention respectively.

FIG. 5 is a topology diagram of a simple subnet with two address configuration modes.

Fig. 6 is a flow chart of the operation steps of the method for selecting and switching the address configuration mode of the IPv6 host in the present invention.

Fig. 7 is a schematic diagram of the host address configuration behavior specification (when C=1) in the embodiment of the present invention.

Fig. 8 is a network topology diagram of a typical scenario of an embodiment of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings.

Referring to Fig. 6, introduce the host selection in the IPv6 network of the present invention and the method for switching address configuration mode:

First add two flag bits in the router announcement RA message of the Neighbor Discovery ND protocol to standardize and identify the host selection and switching address configuration mode: C flag (ControlFlag), that is, the "address configuration control command" field and the S flag Bit (SingleFlag), that is, the "single configuration mode command" field; where:

The S flag indicates that the host only uses one address configuration method, that is, the stateless address automatic configuration mechanism SLAAC is used alone, or the IPv6 dynamic host configuration protocol DHCPv6 is used alone;

The C flag indicates that the RA message has control over the address configuration operation of the host, that is, the host must strictly follow the definitions and instructions of the relevant flags, namely the M, A, C, and S flags;

Then perform the following steps:

Step 1, the router configures the newly added C flag and S flag of the RA message and other fields of the RA message;

Step 2, the router periodically sends RA messages to hosts on the IPv6 link, or sends RA messages to the IPv6 link after the router receives the RS request;

Step 3, after the host receives the RA message, it analyzes the C and S flags in the RA message, and records them in the status bit;

Step 4, the host decides to use the SLAAC mechanism or the DHCPv6 protocol to configure its IPv6 address according to the selection specification of the host address configuration method set by the C and S flags; and even if the host has already used a certain method to configure the IPv6 address, it must follow the specification Switch to the address configuration mode set by this flag.

In order to verify the effectiveness and advantages of the method of the present invention, the applicant has done a simulation embodiment test based on Quagga routing software and Linux platform, and tested it in a typical network environment after implementation.

The operation process of the embodiment of the method of the present invention is: modify the Quagga source code, add and set C and S flags, to realize the router function in the present invention; modify the Linux kernel source code, make the Linux system configure the IPv6 address according to the specification of the present invention, thereby realizing The host function in the present invention.

The emulation that the inventive method is carried out is carried out, also set up typical network environment and carry out test test, referring to Fig. 8, introduce the topological structure of test network environment: single subnet environment, there are two routers RouterA and RouterB in this network, and DHCPv6 server and a host A. Wherein, RouterA and host A implement the functions of the router and the host in the present invention respectively, and both routers can send RA messages to the subnet. Through the RA message, RouterA advertises its prefix 2001:1111::/64 to the subnet; RouterB advertises its prefix 2001:2222::/64 to the subnet. The DHCPv6 server can assign addresses with the prefix 2001:3333::/64 to the hosts in the subnet. Therefore, hosts in this subnet can obtain IPv6 addresses with prefixes 2001:1111::/64 and 2001:2222::/64 from RouterA and B respectively through the SLAAC mechanism, and can also use the DHCPv6 protocol to obtain IPv6 addresses with the prefix 2001 from the DHCPv6 server. :1111::/64 IPv6 address.

Set the flag bit in RouterA, verify whether RouterA can control the host through the RA message to complete the following operations, if it can be completed, it means that the method of the present invention can effectively control the selection and switching of the host to complete the address configuration mode.

(1) The host only uses the DHCPv6 protocol to obtain an IPv6 address;

(2) The host only uses the SLAAC mechanism to configure the IPv6 address;

(3) The host uses the DHCPv6 protocol and the SLAAC mechanism to configure an IPv6 address;

(4) The host finishes switching from using the DHCPv6 protocol to using the SLAAC mechanism;

(5) The host finishes switching from using the SLAAC mechanism to using the DHCPv6 protocol.

During the testing process, using the method of the present invention to set the new flag bits C, S and the original flag bits M, A of the RA message can control the host computer to obtain the configuration mode of the IPv6 address according to the above operations. During the testing process of the embodiment, the specific processes for realizing the above-mentioned various operations are respectively introduced as follows:

(1) The host only uses the DHCPv6 protocol to obtain an IPv6 address (that is, only uses the prefix 2001:3333::/64);

First set the RA message in RouterA so that the three flags C, S, and M are all set to 1, and then host A goes online. The test result is: host A initiates a DHCPv6 session and obtains an IPv6 address through the DHCPv6 server. The test results show that: the host only uses the DHCPv6 protocol to obtain an IPv6 address, which meets the test expectations.

(2) The host only uses the SLAAC mechanism to configure the IPv6 address (that is, the prefixes 2001:1111::/64 and 2001:2222::/64);

Set the RA message in RouterA first, make the C, S, and A flag bits 1, and the M flag bit 0, and then host A goes online. The test result is: after receiving the RA message, host A configures the SLAAC address with the prefix of 2001:1111::/64, and after receiving the RA message from RouterB, the host also configures the prefix of 2001:2222::/64 The test results show that the host can only configure IPv6 addresses through the SLAAC mechanism, which meets the test expectations.

(3) The control host configures the IPv6 address through the DHCPv6 protocol and the SLAAC mechanism;

First set the RA message in RouterA to make its C, M, and A flag positions 1, and its S flag position 0, and then host A goes online. The test result is: after receiving the RA message, host A configures the SLAAC address with the prefix 2001:1111::/64, initiates a DHCPv6 session at the same time, and obtains the IPv6 address with the prefix 2001:3333::/64 through the DHCPv6 server. address. In addition, after receiving the RA message from RouterB, the host also configures an SLAAC address with the prefix 2001:2222::/64. The test results show that the host configures an IPv6 address through the SLAAC mechanism and the DHCPv6 protocol respectively, which meets the test expectations.

(4) The control host finishes switching from using the DHCPv6 protocol to using the SLAAC mechanism;

First set the RA message in RouterA to make its C, S, and M flags set to 1, and then configure the DHCPv6 address for the control host. After the host obtains a stable DHCPv6 address, reset the RA message so that the C, S, and A flags are set to 1, and the M flag is set to 0. Then, check whether the host has switched from using the DHCPv6 protocol to using the SLAAC mechanism. The test result is: after the host receives the reconfiguration RA message, the configuration of the SLAAC address is completed, and the address configured with the DHCPv6 protocol is no longer used. After about 2 hours, the address automatically becomes invalid. The test results show that: the host has completed the switching from using the DHCPv6 protocol to using the SLAAC mechanism, and the test expectation has been realized.

(5) The control host finishes switching from using the SLAAC mechanism to using the DHCPv6 protocol;

Firstly, set the RA message in RouterA so that the C, S, and A flags are set to 1, and the M flag is set to 0, and the control host configures the address through the SLAAC mechanism. After the host obtains a stable SLAAC address, it resets the RA message to make its C, S, and M flags set to 1, and then checks whether the host has completed the switch from using the DHCPv6 protocol to using the SLAAC mechanism. The test results are as follows: After receiving the reconfigured RA message, the host initiates a DHCPv6 session and configures an IPv6 address through the DHCPv6 protocol, and the address originally configured using the SLAAC mechanism is no longer used; about 2 hours later, the The address automatically expires. The test results show that: the host has completed the switching from using the SLAAC mechanism to using the DHCPv6 protocol, and the test expectation has been realized.

In a word, the simulation embodiment test of the method of the present invention is successful, and the purpose of the invention is realized, and the network administrator can control the selection and switching of the host address configuration mode at the network end.

The above description is only the simulation implementation of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (5)

1. a host in the IPv6 network selects and switches the method for address configuration mode, it is characterized in that: the method is: at first in the router announcement RA message of Neighbor Discovery ND agreement, newly-increased two are used for specification and identification host selection and Flag bit for switching address configuration mode: C flag bit (ControlFlag), that is, the "address configuration control command" field and S flag bit (SingleFlag), that is, the "single configuration mode command" field; where: The S flag indicates that the host only uses one address configuration method, that is, the stateless address automatic configuration mechanism SLAAC is used alone, or the IPv6 dynamic host configuration protocol DHCPv6 is used alone; The C flag indicates that the RA message has control over the address configuration operation of the host, that is, the host must strictly follow the definitions and instructions of the relevant flags, namely the M, A, C, and S flags; Then perform the following steps: (1) The router configures the newly added C flag and S flag of the RA message and other fields of the RA message; (2) The router sends RA messages to the host computer on the IPv6 link regularly, or after the router receives the router request RS (RouterSolicitation), it sends the RA message to the IPv6 link; (3) After the host receives the RA message, it analyzes the C and S flags in the RA message, and records them in the status bits; (4) The host decides to use the SLAAC mechanism or the DHCPv6 protocol to configure its IPv6 address according to the selection specification of the host address configuration mode set by the C and S flags; The selection specification of the host address configuration mode set by the C and S flag bits, switch to the address configuration mode set by the M and A flag bits; in this step, the host executes the address configuration mode according to the analyzed C and S flag bits Actions include the following different cases: (4A) If C=0, S=0, the host follows the suggested description of the M flag bit in the standard [RFC2462] and the description of the A flag bit in the standard [RFC4862]: when C=0, S=0, the new None of the additional flags play a role, so follow the original definition of the M and A flags; (4B) If C=0, S=1, because C=0 indicates that the RA message does not have the control right of address configuration, and S=1 indicates that the host should use an address configuration method for address configuration; If M=1, it means that the host only uses the DHCPv6 protocol to configure the address, then the host should initiate a DHCPv6 session or maintain a DHCPv6 address, and does not configure the SLAAC address with the prefix in the RA message; If M=0 and A=1, it means that the host only uses the SLAAC mechanism to configure the address, that is, configure the SLAAC address with the prefix of the RA message, and when the DHCPv6 address expires, it will not renew the contract with the DHCPv6 server; (4C) If C=1, the host configures the address according to the following specifications: C, M, S, and A flag bits can control the host to use DHCPv6, SLAAC, and DHCPv6 and SLAAC to configure the address respectively, and realize different address configuration methods Switching to meet the requirements of host address configuration and network renumbering. 2. The method according to claim 1, characterized in that: the two flag fields of C and S each occupy 1 bit space, and are sequentially set in the reservation on the right side of the existing M and O two fields in the RA message field, and correspond to "Address Configuration Control Command" and "Single Configuration Mode Command" respectively. 3. The method according to claim 1, characterized in that: said step (4C) comprises the following different address configuration methods: (4C1) If M=0 and S=0, the address configuration behavior of the host is not defined or regulated, and the RA message is only an announcement message carrying a network prefix; (4C2) If M=1, S=0, and A=1, the host must use two address configuration methods to configure the IPv6 address, that is, the host uses the RA message to configure the SLAAC address, and at the same time initiates a DHCPv6 session or continues to maintain the DHCPv6 address; (4C3) If M=0, S=1, and A=1, the host only uses the SLAAC mechanism to configure the address; if the host has already configured a DHCPv6 address at this time, the survival time of the DHCPv6 address life cycle should be set to the minimum hour length, so that The DHCPv6 address is expired as early as possible; meanwhile, the host ignores the DHCPv6 configuration of the host by ignoring other RA messages of flag bit C=0; (4C4) If M=1, S=1, the host only uses the DHCPv6 protocol to configure the address; if the host has configured the SLAAC address at this time, the survival time of the SLAAC address life cycle should be set to the minimum hour length, so that the SLAAC address can be used as soon as possible. Expired; at the same time, the host ignores the SLAAC configuration performed on the host by other RA messages with the flag bit C=0. 4. The method according to claim 3, characterized in that: the minimum hour length of the address lifetime in the steps (4C3) and (4C4) is set to 2 hours, if the lifetime of the address is greater than 2 hours, then this Modify the lifetime of the address to 2 hours; if the lifetime of the address is not greater than 2 hours, do not modify it. 5. The method according to claim 1, characterized in that: the basis of the method is based on the RA message sent by the router in the ND protocol, if the host does not receive the RA message when acquiring the address, the host should initiate a DHCPv6 Session, trying to use the DHCPv6 protocol to configure the address to ensure that the host can obtain the address as successfully as possible.