Packet forwarding method, apparatus, and system

1. A packet forwarding method comprising:

receiving, by an ingress provider edge (PE) of an Ethernet virtual private network (EVPN), a first border gateway protocol (BGP) update message sent by a first egress PE of the EVPN, indicating a state of an Ethernet virtual private network instance (EVI) on the first egress PE is active,

wherein the first BGP update message comprises a first network layer reachability information (NLRI) of the EVPN, and

wherein the first NLRI includes (a) a first route type field indicating the first NLRI of the EVPN carries information about the state of the EVI on the first egress PE, (b) a first route distinguisher (RD) field carrying an RD of the EVI on the first egress PE, and (c) a first state indication field having a first value indicating an active state of the EVI on the first egress PE;

determining, by the ingress PE, that a state of the EVI on the first egress PE is active according to the first BGP update message and a state of an EVI on a second egress PE of the EVPN is inactive, wherein the first egress PE comprises a first customer edge (CE) of the EVI of the first egress PE; and

forwarding, by the ingress PE, a broadcast, unknown unicast, and multicast (BUM) packet to the first egress PE, rather than forwarding the BUM packet to the second egress PE, wherein the BUM packet is from the first CE.

2. The method according to claim 1 , wherein the first NLRI includes a first extended community attribute comprising the first type field and the first state indication field.

3. The method according to claim 1 , wherein determining that the state of the EVI on the first egress PE is active comprises:

receiving, by the ingress PE, a second BGP update message sent by the first egress PE,

wherein the second BGP update message indicates a state of a first Ethernet segment (ES),

wherein, when the state of the first ES is active, the first ES is used to forward the BUM packet and, when the state of the first ES is inactive, the first ES is not used to forward the BUM packet, and

wherein the EVI on the first egress PE is connected to a second CE by using the first ES and the EVPN comprises the second CE; and

determining, by the ingress PE, that the state of the EVI on the first egress PE is active when there are multiple first ESs and a state of at least one ES of the first ESs is active.

4. The method according to claim 3 , wherein the second BGP update message comprises a second NLRI of the EVPN comprising a second route type field, a second RD field, an Ethernet signal identifier (ESI) field, and a second state indication field;

wherein a content of the second route type field indicates that the second NLRI of the EVPN carries information about a state of an ES;

wherein the second RD field carries an RD of the EVI on the first egress PE, the ESI field carries a first ESI uniquely identifying the first ES; and

wherein, when content of the second state indication field is a first value, the state of the first ES is active and, when the content of the second state indication field is a second value, the state of the first ES is inactive.

5. The method according to claim 3 , wherein the second BGP update message comprises second EVPN network layer reachability information (NLRI) and a second extended community attribute corresponding to the second EVPN NLRI;

wherein the second EVPN NLRI comprises a second route distinguisher (RD) field and an ESI field;

wherein the second extended community attribute comprises a second type field and a second state indication field;

wherein a content of the second type field indicates that the second extended community attribute carries information about a state of an ES;

wherein the second RD field carries an RD of the EVI on the first egress PE;

wherein the ESI field carries a first ESI uniquely identifying the first ES; and

wherein, when content of the second state indication field is a first value, the state of the first ES is active and, when the content of the second state indication field is a second value, the state of the first ES is inactive.

6. In a packet forwarding system including an Ethernet virtual private network instance (EVI) comprising an ingress provider edge (PE), a first egress PE, and a second egress PE of an Ethernet virtual private network (EVPN) comprising a first customer edge (CE), wherein the ingress PE is configured to:

receive a first border gateway protocol (BGP) update message from the second egress PE, wherein the first BGP update message indicates a state of the EVI on the second egress PE is inactive;

receive a second BGP update message from the first egress PE, wherein the second BGP update message indicating a state of a first Ethernet segment (ES) in the EVI connecting the first or second egress PE to a customer edge (CE) of the EVPN, wherein when the state of the first ES is active, the first ES is used to forward the BUM packet and, when the state of the first ES is inactive, the first ES is not used to forward the BUM packet;

determine, according to the first and second BGP update messages, that a state of the EVI on the first egress PE is active and a state of the EVI on a second egress PE is inactive when there are multiple first ESs and a state of at least one ES of the first ESs is active; and

forward a broadcast, unknown unicast, and multicast (BUM) packet to the first egress PE, rather than forwarding the BUM packet to the second egress PE, wherein the BUM packet is from the first CE.

7. A provider edge (PE) device is an ingress PE in an Ethernet virtual private network instance (EVI) of an Ethernet virtual private network (EVPN) that includes a first customer edge (CE) and a second CE, the PE comprising a receiver, a memory and a processor, wherein the memory is configured to store program code, and the processor is configured to execute the program code and cooperate with the receiver to provide at least the following operations:

receiving a second border gateway protocol (BGP) update message sent by a first egress PE,

wherein the second BGP update message indicates a state of a first Ethernet segment (ES), an active state causing the first ES to forward a broadcast, unknown unicast and multicast (BUM) packet when the state of the first ES is active and an inactive state causing the first ES to not forward the BUM packet, and

wherein the EVI on the first egress PE is connected to the second CE by using the first ES;

determining that a state of the EVI on the first egress PE is active according to the second BGP update message and a state of the EVI on a second egress PE is inactive when there are multiple first ESs and a state of at least one ES of the first ESs is active; and

forwarding the BUM packet to the first egress PE, rather than forwarding the BUM packet to the second egress PE, where the BUM packet is from the first CE.

8. The PE of claim 7 , wherein the processor is configured to execute the program code and cooperate with the receiver to provide the following further operations:

receiving a first BGP update message sent by the first egress PE, where the first BGP update message indicates that the state of the EVI on the first egress PE is active; and

determining, according to the first BGP update message that the state of the EVI on the first egress PE is active.

9. In the packet forwarding system of claim 6 , wherein the second BGP update message comprises a second EVPN network layer reachability information (NLRI), the second EVPN NLRI comprises a second route type field, a second route distinguisher (RD) field, an Ethernet signal identifier (ESI) field, and a second state indication field;

wherein content of the second route type field indicates that the second EVPN NLRI carries information about a state of an ES;

wherein the second RD field carries an RD of the EVI on the first egress PE, the ESI field carries a first ESI uniquely identifying the first ES; and

wherein, when the content of the second state indication field is a first value, the state of the first ES is active and, when the content of the second state indication field is a second value, the state of the first ES is inactive.

10. In the packet forwarding system of claim 6 , wherein the second BGP update message comprises second EVPN network layer reachability information (NLRI) and a second extended community attribute corresponding to the second EVPN NLRI, the second EVPN NLRI comprises a second route distinguisher (RD) field and an Ethernet signal identifier (ESI) field, the second extended community attribute comprises a second type field and a second state indication field;

wherein content of the second type field indicates that the second extended community attribute carries information about a state of an ES, the second RD field carries an RD of the EVI on the first egress PE, and the ESI field carries a first ESI uniquely identifying the first ES; and

wherein, when content of the second state indication field is a first value, the state of the first ES is active and, when the content of the second state indication field is a second value, the state of the first ES is inactive.