CN106572012A - VPN FRR implementation method and PE equipment - Google Patents

Abstract

The embodiment of the invention discloses a method for realizing VPN FRR and PE equipment, which relate to the field of communication technology and are used to realize VPN FRR protection when a user side link fails, thereby preventing flow loss. The method includes: the source PE device receives the routing information including the first user-side link information issued by the active target PE device and the routing information including the second user-side link information issued by the standby target PE device; The information generates corresponding forwarding items and sends them to the forwarding engine. The forwarding items include primary and backup forwarding information; when the source PE device learns that the first user-side link is unavailable, the source PE device will Set it to the unavailable flag, so that when the forwarding engine hits the forwarding item, if it detects that the status flag corresponding to the forwarding item is unavailable, it will forward the traffic according to the standby forwarding information in the forwarding item.

Description

A method for implementing VPN FRR and PE equipment

technical field

The present invention relates to the technical field of communication, and in particular to a method for realizing fast rerouting VPN FRR of a virtual private network and PE equipment.

Background technique

Today, with the rapid development of the network, operators attach great importance to the speed of service convergence when the network fails. When any node fails, the service switching of adjacent nodes is less than 50ms, and the end-to-end service convergence is less than 1s. Threshold-level indicators.

In order to meet the requirement of less than 50ms for adjacent node service switching and less than 1s for end-to-end service convergence, MPLS TEFRR multi-protocol label switching traffic engineering fast rerouting, where: MPLS is the English abbreviation of Multi-Protocol Label Switching, that is, multi-protocol label switching ; TE is the English abbreviation of Traffic Engineering, that is, traffic engineering; FRR is the English abbreviation of Fast Re-Route, that is, fast rerouting) technology, and IGP (Interior Gateway Protocol, interior gateway protocol) route rapid convergence technology (IP FRR). However, none of them can solve the problem of rapid end-to-end service convergence when a PE device node fails in a CE (Customer Edge, user network edge) dual-homing PE (Provider Edge, service provider network edge) network.

The existing VPN (Virtual Private Network, virtual private network) FRR is a means to solve the problem of end-to-end service convergence in the common network model of CE dual-homing. Switch to the backup path, so that the convergence time of the end-to-end service in the case of a PE node failure is controlled within 1s.

Specifically, in the VPN FRR technology, as shown in Figure 1, the primary path for CE1 to access CE2 is CE1-PE1-PE2-CE2, and the backup path is CE1-PE1-PE3-CE2 as an example; when PE2 does not fail , the path from CE1 to CE2 is the primary path, and when PE2 fails, the path from CE1 to CE2 is quickly switched to the backup path.

However, when VPN FRR technology is used, fast switching of VPN services can only be performed for node failures (PE equipment failures), but VPN service fast switching cannot be performed for user-side link failures (link failures between PE equipment and CE equipment) . When the link on the user side fails, the access path is still the main path CE1-PE1-PE2-CE2, that is, the traffic will still be forwarded to PE2 along the CE1-PE1-PE2 path, and the outbound interface on PE2 will causing packet loss. To restore the service transmission between CE1 and CE2, route convergence is required, and the convergence time is limited by the number of VPN routes. If the convergence time is too long, packet loss will occur.

Contents of the invention

Embodiments of the present invention provide a virtual private network fast rerouting VPN FRR implementation method and PE equipment, which are used to implement VPN FRR protection when a user-side link fails, thereby preventing traffic loss.

In order to achieve the above object, embodiments of the present invention adopt the following technical solutions:

In the first aspect, the implementation of the present invention provides a virtual private network fast rerouting VPN FRR implementation method, which is applied to the network of user network edge CE dual-homing service provider network edge PE, including source CE equipment, source PE equipment, A target CE device, an active target PE device and a standby target PE device; the method includes:

The source PE device receives the routing information directed to the target CE device issued by the active target PE device and the backup target PE device, and the routing information issued by the active target PE device includes: the first user side chain route information, used to indicate the link between the active target PE device and the target CE device, and the routing information released by the backup target PE device includes: second user-side link information, used to indicate the backup A link between the target PE device and the target CE device;

The source PE device generates a corresponding forwarding item according to the routing information, and sends it to the forwarding engine. The forwarding item includes the active forwarding information generated according to the routing information published by the active target PE device and the Backup forwarding information generated by the routing information published by the backup target PE device;

When the source PE device learns that the first user-side link is unavailable, the source PE device sets the status flag corresponding to the forwarding item in the forwarding engine to an unavailable flag, so that the forwarding engine hits the forwarding item, if it is detected that the status flag corresponding to the forwarding item is unavailable, traffic forwarding is performed according to the standby forwarding information in the forwarding item.

In the second aspect, the implementation of the present invention provides a PE device, which is applied to the network of the user network edge CE dual-homing service provider network edge PE, and the network includes a source PE device, a target CE device, an active target PE device, and Standby target PE equipment; the PE equipment is used as the source PE equipment, and the equipment includes:

a receiving unit, configured to receive routing information directed to the target CE device issued by the active target PE device and the backup target PE device, where the routing information issued by the active target PE device includes: a first user side chain route information, used to indicate the link between the active target PE device and the target CE device, and the routing information released by the backup target PE device includes: second user-side link information, used to indicate the backup A link between the target PE device and the target CE device;

A generation unit, configured to generate a corresponding forwarding item according to the routing information, and issue it to the forwarding engine, where the forwarding item includes the active forwarding information generated according to the routing information issued by the active target PE device and the forwarding item according to the Backup forwarding information generated by the routing information published by the backup target PE device;

A setting unit, configured to set the status flag corresponding to the forwarding item in the forwarding engine as an unavailable flag when learning that the first user-side link is unavailable, so that when the forwarding engine hits the forwarding item, if it detects If the state flag corresponding to the forwarding item is an unavailable flag, traffic forwarding is performed according to the standby forwarding information in the forwarding item.

The embodiment of the present invention provides a virtual private network fast rerouting VPN FRR implementation method and a PE device, by adding a user side chain indicating the link between the target PE device and the target CE device in the routing information published by the target PE device Route information, so that the source PE device generates a corresponding forwarding item according to the routing information, and sends it to the forwarding engine. The forwarding items include the active forwarding information generated according to the routing information released by the active target PE device and the backup forwarding information generated according to the routing information released by the backup target PE device. In this way, the active forwarding information in the forwarding item includes the first user-side link information, and the standby forwarding information includes the second user-side link information. When the source PE device learns that the first user-side link is unavailable, the source PE device sets the status flag corresponding to the forwarding item in the forwarding engine as an unavailable flag, so that when the forwarding engine hits the forwarding item, if it detects that the forwarding item corresponds to If the status flag of the forwarding item is unavailable, the traffic is forwarded according to the standby forwarding information in the forwarding item. Therefore, for the problem of user-side link failure, VPN FRR protection is implemented to prevent traffic loss.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

FIG. 1 is a schematic diagram of VPN FRR switching for node failure in a CE dual-homing PE network in the prior art;

FIG. 2 is a schematic diagram of VPN FRR switching for user-side link failure in a CE dual-homing PE network provided by an embodiment of the present invention;

FIG. 3 is a flowchart of a method for implementing VPN FRR provided by an embodiment of the present invention;

Fig. 4 is a block diagram of a PE device provided by an embodiment of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The term "and/or" in the embodiment of the present invention is only a kind of association relationship describing associated objects, which means that there may be three kinds of relationships, for example, A and/or B, which can mean: A exists alone, and A and B exist at the same time , there are three cases of B alone. In addition, the character "/" in the embodiment of the present invention generally indicates that the contextual objects are an "or" relationship.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

Embodiment one

The embodiment of the present invention provides a virtual private network fast rerouting VPN FRR implementation method, by adding user-side link information in the forwarding item, when the first user-side link is unavailable, the source PE device forwards the forwarding engine The status flag corresponding to the item is set as an unavailable flag, so that when the forwarding engine hits the forwarding item, if it detects that the status flag corresponding to the forwarding item is unavailable, it will forward the traffic according to the standby forwarding information in the forwarding item. In this way, VPN FRR is realized, and the problem of packet loss when the link on the user side fails is solved.

The embodiment of the present invention will be described in detail below by taking the network of CE dual-homing service provider network edge PE shown in FIG. 2 as an example. In this network architecture, user CEs and PEs directly establish EBGP neighbors. The source CE device is CE1, the source PE device is PE1, the primary target PE device is PE1, the standby target PE device is PE2, and the target CE devices are CE2 and CE3. It can be seen that links are established between the active target PE device and multiple target CE devices in this architecture, for example, links are established between PE1 and CE2 and CE3 at the same time. Among them, PE1 and PE2 are mutually configured as peer PE devices, and PE1 and PE3 are mutually configured as peer PE devices.

It should be noted that, in this embodiment of the present invention, one backup target PE device is used as an example for illustration, but it is not limited to one, and there may be multiple backup target PE devices; at the same time, there may be a or multiple P devices, which will not be repeated here. As shown in Figure 3, the method specifically includes:

S101. The source PE device receives routing information directed to the target CE device issued by the active target PE device and the backup target PE device.

In the existing VPN FRR technology, the routing information directed to the target CE device published by the active target PE device and the backup target PE device includes address information of the routing device, such as the address information of the active target PE device.

For example, as shown in FIG. 2 , PE2/PE3 advertises the routing information of the device (including address information of PE2/PE3, next-hop address information of PE2/PE3, etc.) to PE1.

For example, both PE2 and PE3 advertise routing information pointing to CE2 to PE1 and assign private network labels. PE1 generates VPN FRR routing entries based on the routing information directed to CE2 advertised by PE2 and PE3.

Then in the existing VPN FRR technology, the key content of the VPN FRR routing table entry generated by PE1 is shown in Table 1 (parameters are for example):

Table 1

RoutingTable (routing table): VPN1 routing table entry 1 Destination (destination address): 10.3.1.0/24 Protocol (protocol): IBGP ProcessID (process ID): 0 Preference (parameter): 255 Cost (overhead): 0 NextHop (next hop): 2.2.2.2 Neighbor: 2.2.2.2 Label (label): 15361 BkNextHop (alternate next hop): 3.3.3.3 BkLabel (alternate label): 15362 routing table entry 2 Destination (destination address): 11.3.1.0/24 Protocol (protocol): IBGP ProcessID (process ID): 0 Preference (parameter): 255 Cost (overhead): 0 NextHop (next hop): 2.2.2.2 Neighbor: 2.2.2.2 Label (label): 15371 BkNextHop (alternate next hop): 3.3.3.3 BkLabel (alternate label): 15372

In the VPN FRR technology provided by the embodiment of the present invention, the routing information released by the active target PE device also includes: first user-side link information, used to indicate the link between the active target PE device and the target CE device, and the backup The routing information published by the target PE device includes: second user-side link information, which is used to indicate the link between the standby target PE device and the target CE device.

For example, as shown in Figure 2, taking CE1 accessing CE2 as an example, the routing information published by PE2 includes: first user side link information, which can be represented by PE_Nexthop, used to indicate the link between PE2 and CE2, the link between PE2 and CE2 The inter-link can be represented by Link A. PE_Nexthop can be the outgoing interface address of PE2 on Link A, or the incoming interface address of CE2 on Link A. In the embodiment of the present invention, the PE_Nexthop of Link A is 4.4.4.4. The routing information released by PE3 includes: second user side link information, which can also be represented by BkPE_Nexthop, used to indicate the link between PE3 and CE2, and the link between PE3 and CE2 can be represented by Link B. BkPE_Nexthop can be the outgoing interface address of PE3 on Link B, or the incoming interface address of CE2 on Link B. In the embodiment of the present invention, the BkPE_Nexthop of Link B is 5.5.5.5. Similarly, when CE1 accesses CE3, the routing information advertised by PE2 and PE3 changes accordingly.

The key content of the VPN FRR routing entry generated by PE1 is shown in Table 2:

Table 2

S102. The source PE device generates a corresponding forwarding item according to the routing information, and delivers it to the forwarding engine.

Specifically, the source PE device generates corresponding forwarding entries according to the VPN FRR routing table entry, the routing information published by the active target PE device, the routing information released by the standby target PE device, and the egress/ingress port information of each device.

The forwarding item includes active forwarding information generated according to the routing information advertised by the active target PE device and standby forwarding information generated according to the routing information advertised by the standby target PE device.

For example, as shown in Figure 2, PE1 generates primary forwarding information according to VPN FRR routing entries (NextHop, PE_Nexthop, etc.), routing information published by PE2, outgoing interface and incoming interface of the link between PE1 and PE2; PE1 Generate backup forwarding information based on VPNFRR routing table entries (BkNextHop, BkPE_Nexthop), routing information advertised by PE3, outgoing interface and incoming interface of the link between PE1 and PE3.

It should be noted that in the embodiment of the present invention, user-side link information, such as PE_Nexthop and BkPE_Nexthop, is added to the generated forwarding item, and other information in the forwarding item can refer to the prior art.

S103 (optional). The source PE device receives a notification that the first user-side link is unavailable.

When the active target PE detects that the first user-side link is unavailable by using the BFD technology. The source PE device receives a notification that the first user-side link is unavailable.

It should be noted that in the embodiment of the present invention, the active target PE device may also use other technologies than the BFD technology, such as MPLS OAM technology to detect whether the first user side link is available.

For example, as shown in Figure 2, BFD for IP is configured on LinkA of PE2 to check whether the peer IP address 4.4.4.4 is available. Then in the case of Link A link failure, after PE2 detects the link failure through BFD technology, PE2 confirms that PE_Nexthop=4.4.4.4 is unavailable, and then notifies PE1, and PE1 receives the notification that PE_Nexthop=4.4.4.4 is unavailable.

S104. When the source PE device learns that the first user-side link is unavailable, the source PE device sets a status flag corresponding to the forwarding item in the forwarding engine as an unavailable flag.

So that when the forwarding engine hits the forwarding item, if it detects that the status flag corresponding to the forwarding item is an unavailable flag, it forwards the traffic according to the backup forwarding information in the forwarding item.

For example, as shown in FIG. 2 , when PE1 learns that the first user-side link PE_Nexthop=4.4.4.4 in the active forwarding information is unavailable, PE1 sets the status flag corresponding to the forwarding item in the forwarding engine as an unavailable flag. When the forwarding engine hits the forwarding item, it detects the status flag corresponding to the forwarding item, and if it is an unavailable flag, forwards the traffic according to the backup forwarding information in the forwarding item.

Preferably, a state table is set in the source PE device, and a state flag is recorded in the state table.

The source PE device setting the status flag corresponding to the forwarding item in the forwarding engine as an unavailable flag includes: when the source PE device learns that the first user-side link is unavailable, setting the status flag used to indicate that the first user-side link is unavailable The state flag is set as an unavailable flag, and the updated state table is sent to the forwarding engine.

For example, as shown in FIG. 2 , a state table is set in PE1, and a state flag is recorded in the state table. Each state flag recorded in the state table corresponds to each forwarding entry in the forwarding table, and the state flag indicates whether the active forwarding information of the corresponding forwarding entry is available. When PE1 learns that the first user-side link PE_Nexthop=4.4.4.4 between PE2 and CE2 is unavailable, then the status flag used to indicate that the first user-side link is unavailable in the status table is set as an unavailable flag, and the The updated state table is sent to the forwarding engine. Preferably, when the source PE device learns that the label switching path LSP outer layer tunnel between the source PE device and the active target PE device is unavailable, the state flag used to indicate that the first user side link is unavailable in the state table is set to Logo not available.

That is to say, in a CE dual-homing PE network, the same status flag can be used for the node failure and the user side link failure in the active forwarding information, and different status flags can also be set. For example, when PE1 perceives that the outer tunnel between PE1 and PE2 is unavailable through technologies such as BFD and MPLSOAM, it sets the corresponding flag in the LSP tunnel status table as unavailable and sends it to the forwarding engine, and the forwarding engine hits a After the forwarding item, check the status of the LSP tunnel corresponding to the forwarding item, and if it is unavailable, use the backup forwarding information carried in the forwarding item for forwarding. In this way, the packet will be marked with the inner layer label assigned by PE3, switched to PE3 along the outer LSP tunnel between PE1 and PE3, and then forwarded to CE2, so as to restore the service from CE1 to CE2, and implement PE2 node failure. Fast convergence of end-to-end services. Configure the BFD for IP protocol on PE2 to detect whether PE_Nexthop is available. When PE_Nexthop is unavailable, trigger VPN FRR based on the PE_Nexthop address. You can also set the corresponding flag in the corresponding LSP tunnel status table as unavailable and send it to the forwarding engine. , after the forwarding engine hits a forwarding item, it checks the status of the LSP tunnel corresponding to the forwarding item. If it is unavailable, it forwards using the backup forwarding information carried in this forwarding item, so as to realize the end-to-end link failure in the case of user-side link failure. Rapid convergence of terminal services.

Of course, when the link failure on the user side causes PE_Nexthop to be unavailable, a new status flag different from node failure can also be used to indicate whether the active forwarding information of the corresponding forwarding item is available.

For example, as shown in FIG. 2, PE2 establishes links with CE2 and CE3 at the same time. When it is detected that PE_Nexthop=4.4.4.4 is unavailable, the status flag corresponding to forwarding item 1 in Table 2 is set as an unavailable flag , and the status flag corresponding to forwarding item 2 is still available. Then, when the forwarding engine hits the forwarding item 1, PE1 detects that the status flag of the forwarding item 1 is an unavailable flag, and uses the backup forwarding information BkNextHop=3.3.3.3 and BkPE_Nexthop=6.6.6.6 of the forwarding item 1 to forward traffic. When the forwarding engine hits forwarding item 2, PE1 detects that the status flag of forwarding item 2 is available, and still uses the active forwarding information NextHop=2.2.2.2 and PE_Nexthop=5.5.5.5 of forwarding item 2 to forward traffic.

It can be seen that, in the implementation method of VPN FRR provided by the embodiment of the present invention, when links are established between the active PE device and multiple target CE devices at the same time, when one or more user-side links fail, only the Implement VPN FRR protection on the faulty link, and other links will not be affected.

The embodiment of the present invention provides a virtual private network fast rerouting VPN FRR implementation method, by adding user-side link information in the forwarding item, when the first user-side link is unavailable, VPN FRR protection is realized, solving the problem of Packet loss when the link on the user side fails.

Embodiment two

An embodiment of the present invention provides a PE device, which is applied to a network of a user network edge CE dual-homing service provider network edge PE, and the network includes a source PE device, a target CE device, an active target PE device, and a backup target PE device ; The PE device is used as the source PE device, and the implementation of each functional module in the device can refer to the first embodiment above, which will not be repeated here. The equipment shown in Figure 4 includes:

The receiving unit 11 is configured to receive routing information directed to the target CE device issued by the active target PE device and the backup target PE device, where the routing information issued by the active target PE device includes: the first user side link information, used to indicate the link between the active target PE device and the target CE device, and the routing information released by the standby target PE device includes: second user side link information, used to indicate the A link between the backup target PE device and the target CE device;

The generating unit 12 is configured to generate a corresponding forwarding item according to the routing information received by the receiving unit 11, and send it to the forwarding engine, and the forwarding item includes the routing information generated according to the routing information released by the active target PE device. The active forwarding information and the standby forwarding information generated according to the routing information released by the standby target PE device;

The setting unit 13 is configured to set the status flag corresponding to the forwarding item generated by the generating unit 12 in the forwarding engine as an unavailable flag when it is known that the first user-side link is unavailable, so that the forwarding engine hits When the forwarding item is detected, if it is detected that the status flag corresponding to the forwarding item is an unavailable flag, traffic forwarding is performed according to the standby forwarding information in the forwarding item.

Optionally, a state table is set in the source PE device, and a state flag is recorded in the state table;

The setting unit 13 is also configured to set the status flag used to indicate that the first user-side link is unavailable in the status table as an unavailable flag when it is known that the first user-side link is unavailable; The subsequent state table is sent to the forwarding engine.

Optionally, the setting unit 13 is further configured to use the status table to indicate the The unavailable state flag of the first user-side link is set as an unavailable flag.

That is to say, when the LSP outer tunnel is unavailable, or the first user-side link is unavailable, corresponding to the same status flag in the status table, the status flag in the status table is set as an unavailable flag. Certainly also can correspond to different status flags, when the LSP outer layer tunnel is unavailable, its corresponding status flag is set as an unavailable flag; when the first user side link is unavailable, its corresponding state flag is set as an unavailable flag .

Optionally, links are established between the active target PE device and multiple target CE devices.

Optionally, the receiving unit 11 is further configured to, when the active target PE device detects that the first user-side link is unavailable using the bidirectional forwarding detection (BFD) technology, receive the unavailable link of the first user-side link. Notices used.

It should be noted that the receiving unit 11 in this embodiment may be an interface circuit with a receiving function on the PE device, such as a receiver or an information receiving interface. Other units can be independently established processors, or can be integrated in a certain processor of the PE device. In addition, they can also be stored in the memory of the PE device in the form of program code, and called by a certain processor of the PE device. And execute the functions of the above units. The processor mentioned here can be a central processing unit (English full name: Central Processing Unit, English abbreviation: CPU), or a specific integrated circuit (English full name: Application Specific Integrated Circuit, English abbreviation: ASIC), or a configured One or more integrated circuits implementing embodiments of the invention.

The embodiment of the present invention provides a PE device. By adding user-side link information in the forwarding item, when the first user-side link is unavailable, VPN FRR protection is realized, and packet loss when the user-side link fails is solved. question.

In the several embodiments provided in this application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or May be integrated into another system, or some features may be ignored, or not implemented. In another point, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, each unit may be physically included separately, or two or more units may be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware, or in the form of hardware plus software functional units.

The above-mentioned integrated units implemented in the form of software functional units may be stored in a computer-readable storage medium. The above-mentioned software functional units are stored in a storage medium, and include several instructions to enable a computer device (which may be a personal computer, server, or network device, etc.) to execute some steps of the methods described in various embodiments of the present invention. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (Read-Only Memory, referred to as ROM), random access memory (Random Access Memory, referred to as RAM), magnetic disk or optical disk, etc., which can store program codes. medium.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (10)

1. An implementation method of virtual private network fast rerouting VPN FRR, which is applied to the network of user network edge CE dual-homing service provider network edge PE, including source CE equipment, source PE equipment, target CE equipment, and active target PE equipment and standby target PE equipment; it is characterized in that, the method comprises: The source PE device receives the routing information directed to the target CE device issued by the active target PE device and the backup target PE device, and the routing information issued by the active target PE device includes: the first user side chain route information, used to indicate the link between the active target PE device and the target CE device, and the routing information released by the backup target PE device includes: second user-side link information, used to indicate the backup A link between the target PE device and the target CE device; The source PE device generates a corresponding forwarding item according to the routing information, and sends it to the forwarding engine. The forwarding item includes the active forwarding information generated according to the routing information published by the active target PE device and the Backup forwarding information generated by the routing information published by the backup target PE device; When the source PE device learns that the first user-side link is unavailable, the source PE device sets the status flag corresponding to the forwarding item in the forwarding engine to an unavailable flag, so that the forwarding engine hits the forwarding item, if it is detected that the status flag corresponding to the forwarding item is unavailable, traffic forwarding is performed according to the standby forwarding information in the forwarding item. 2. The method according to claim 1, wherein a state table is set in the source PE device, and a state flag is recorded in the state table; The source PE device setting the state flag corresponding to the forwarding item in the forwarding engine as an unavailable flag includes: When the source PE device learns that the first user-side link is unavailable, set a status flag in the status table for indicating that the first user-side link is unavailable as an unavailable flag; Sending the updated state table to the forwarding engine. 3. The method according to claim 2, wherein the method further comprises: When the source PE device learns that the label switched path LSP outer tunnel between the source PE device and the active target PE device is unavailable, use the status table to indicate that the first user-side link is unavailable The status flag is set to unavailable. 4. The method according to claim 1, wherein links are established between the active target PE device and multiple target CE devices. 5. The method according to claim 1, wherein the method further comprises: When the active target PE device detects that the first user-side link is unavailable by using a BFD technology; the source PE device receives a notification that the first user-side link is unavailable. 6. A PE device, applied to the network of user network edge CE dual-homing service provider network edge PE, the network includes source PE equipment, target CE equipment, active target PE equipment and backup target PE equipment; the PE The device is used as the source PE device, and it is characterized in that the device includes: a receiving unit, configured to receive routing information directed to the target CE device issued by the active target PE device and the standby target PE device, where the routing information issued by the active target PE device includes: a first user side chain route information, used to indicate the link between the active target PE device and the target CE device, and the routing information released by the backup target PE device includes: second user-side link information, used to indicate the backup A link between the target PE device and the target CE device; A generation unit, configured to generate a corresponding forwarding item according to the routing information, and issue it to the forwarding engine, where the forwarding item includes the active forwarding information generated according to the routing information published by the active target PE device and the forwarding item according to the Backup forwarding information generated by the routing information published by the backup target PE device; A setting unit, configured to set the status flag corresponding to the forwarding item in the forwarding engine as an unavailable flag when learning that the first user-side link is unavailable, so that when the forwarding engine hits the forwarding item, if it detects If the state flag corresponding to the forwarding item is an unavailable flag, traffic forwarding is performed according to the standby forwarding information in the forwarding item. 7. The device according to claim 6, wherein a state table is set in the source PE device, and a state flag is recorded in the state table; The setting unit is also configured to set the status flag in the status table used to indicate that the first user-side link is unavailable as an unavailable flag when it is known that the first user-side link is unavailable; The state table of is sent to the forwarding engine. 8. The device according to claim 7, wherein the setting unit is further configured to know that the label switching path (LSP) outer tunnel between the source PE device and the active target PE device is unavailable , setting the status flag in the status table used to indicate that the first user-side link is unavailable as an unavailable flag. 9. The device according to claim 6, wherein links are established between the active target PE device and multiple target CE devices. 10. The device according to claim 6, wherein the receiving unit is further configured to detect that the first user-side link is unavailable when the primary target PE device detects that the first user-side link is unavailable by using a bidirectional forwarding detection (BFD) technology, Receive a notification that the first user-side link is unavailable.