A service node (3, 600), wherein the service node (3, 600) includes and is configured to run a virtual router, a virtual switch and a plurality of destination backend servers including a selected destination backend server, the selected destination backend server having been allocated by a load balancer to a client to provide a service, and an IP address of a logical interface of the selected destination backend server is a virtual IP address of the load balancer; the destination backend servers belong to different tenant networks, and the destination backend servers of the different tenant networks are distinguished by using local area network IP addresses, the destination backend servers each comprise a virtual network interface card, all the virtual network interface cards use a same IP address which is an IP address of the virtual network interface cards; the service node (3, 600), on which the selected destination backend server is located, is configured to receive a service access request from the load balancer and to forward the service access request to the virtual router on the service node (3, 600), a destination address of the service access request is the local area network IP address of the selected destination backend server and a source IP address of the service access request is a public IP address of the client; the virtual router is configured to receive, from the service node (3, 600) the service access request, and change the destination address of the service access request from the local area network IP address of the selected destination backend server to the IP address of the virtual network interface card of the selected destination backend server according to a first flow table, and is further configured to send the service access request to the virtual switch; the virtual switch on the service node (3, 600) is configured to receive the service access request from the virtual router, the virtual switch is further configured to: change, according to a second flow table, the destination address of the service access request to the virtual IP address of the load balancer being the IP address of the logical interface of the selected destination backend server, and send the service access request to the selected destination backend server; and the selected destination backend server is configured to: receive and process the service access request sent by the virtual switch, and return a service access response to the client; wherein the selected destination backend server is further configured to send the service access response first to the virtual router on the service node (3, 600), and the virtual router is configured to change a source address of the service access response to a public IP address of the load balancer according to a third flow table, and the virtual router is configured to send the service access response to the client. the destination backend servers belong to different tenant networks, and the destination backend servers of the different tenant networks are distinguished by using local area network IP addresses, the destination backend servers each comprise a virtual network interface card, all the virtual network interface cards use a same IP address which is an IP address of the virtual network interface cards; the service node (3, 600), on which the selected destination backend server is located, is configured to receive a service access request from the load balancer and to forward the service access request to the virtual router on the service node (3, 600), a destination address of the service access request is the local area network IP address of the selected destination backend server and a source IP address of the service access request is a public IP address of the client; the virtual router is configured to receive, from the service node (3, 600) the service access request, and change the destination address of the service access request from the local area network IP address of the selected destination backend server to the IP address of the virtual network interface card of the selected destination backend server according to a first flow table, and is further configured to send the service access request to the virtual switch; the virtual switch on the service node (3, 600) is configured to receive the service access request from the virtual router, the virtual switch is further configured to: change, according to a second flow table, the destination address of the service access request to the virtual IP address of the load balancer being the IP address of the logical interface of the selected destination backend server, and send the service access request to the selected destination backend server; and the selected destination backend server is configured to: receive and process the service access request sent by the virtual switch, and return a service access response to the client; wherein the selected destination backend server is further configured to send the service access response first to the virtual router on the service node (3, 600), and the virtual router is configured to change a source address of the service access response to a public IP address of the load balancer according to a third flow table, and the virtual router is configured to send the service access response to the client.