A virtual cluster establishment method, comprising: establishing, by a first network device, a network-layer-based first communication connection with a second network device; sending, by the first network device, a first registration request message to the second network device through the first communication connection, wherein the first registration request message is used to request to establish a virtual cluster with the second network device; after the first network device receives a first registration response message sent by the second network device, wherein the first registration response message indicates that the virtual cluster is successfully established, selecting the second network device as an active main control device of the first network device in the virtual cluster; establishing, by the first network device, a network-layer-based second communication connection with a third network device; sending, by the first network device, a second registration request message to the third network device through the second communication connection, wherein the second registration request message is used to request the third network device to join the virtual cluster; and after the first network device receives a second registration response message sent by the third network device, selecting the third network device as a standby main control device of the first network device in the virtual cluster; wherein the selecting the second network device as an active main control device of the first network device in the virtual cluster system specifically comprises: forwarding, by the first network device, a control protocol packet received from a network device outside the virtual cluster to the second network device through the first communication connection, so that the second network device generates an external forwarding table of the virtual cluster according to the control protocol packet; and receiving, by the first network device, the external forwarding table of the virtual cluster that is sent by the second network device. establishing, by a first network device, a network-layer-based first communication connection with a second network device; sending, by the first network device, a first registration request message to the second network device through the first communication connection, wherein the first registration request message is used to request to establish a virtual cluster with the second network device; after the first network device receives a first registration response message sent by the second network device, wherein the first registration response message indicates that the virtual cluster is successfully established, selecting the second network device as an active main control device of the first network device in the virtual cluster; establishing, by the first network device, a network-layer-based second communication connection with a third network device; sending, by the first network device, a second registration request message to the third network device through the second communication connection, wherein the second registration request message is used to request the third network device to join the virtual cluster; and after the first network device receives a second registration response message sent by the third network device, selecting the third network device as a standby main control device of the first network device in the virtual cluster; wherein the selecting the second network device as an active main control device of the first network device in the virtual cluster system specifically comprises: forwarding, by the first network device, a control protocol packet received from a network device outside the virtual cluster to the second network device through the first communication connection, so that the second network device generates an external forwarding table of the virtual cluster according to the control protocol packet; and receiving, by the first network device, the external forwarding table of the virtual cluster that is sent by the second network device. forwarding, by the first network device, a control protocol packet received from a network device outside the virtual cluster to the second network device through the first communication connection, so that the second network device generates an external forwarding table of the virtual cluster according to the control protocol packet; and receiving, by the first network device, the external forwarding table of the virtual cluster that is sent by the second network device.