DATA CENTER NETWORK SYSTEM AND PACKET FORWARDING METHOD THEREOF

• US 20130136126A1
• Filed: 11/30/2011
• Published: 05/30/2013
• Est. Priority Date: 11/30/2011
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Tu, Cheng-Chun, Chiueh, Tzi-Cker, Wang, Yu-Cheng
• Granted Patent: US 8,767,737 B2
• Time in Patent Office: Days
• US Class Current: 370/392
• CPC Class Codes: G06F 2009/45595 Network integration; Enabling network access in virtual machine instances
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects
• CPC Class Codes: H04L 61/103 across network layers, e.g. resolution of network layer into physical layer addresses or address resolution protocol [ARP]

Abstract

A data center network system and a packet forwarding method thereof are provided. The data center network system includes a virtual bridge and an address resolution protocol (ARP) server. The virtual bridge intercepts an ARP request having an identification field and a destination IP address field and adds a corresponding virtual data center identification to the identification field of the ARP request and redirecting the ARP request to the ARP server. Additionally, the ARP server queries a corresponding MAC address according to an IP address recorded in the destination IP address field of the ARP request and the corresponding VDCID recorded in the identification field of the ARP request, and transmits the corresponding MAC address in response to the ARP request. Accordingly, the same private IP address can be reused in the data center network system.

Claims

1. A data center network system, comprising:

a virtual bridge, connected to a network;

an ARP server, connected to the network; and

a virtual machine, executed on a physical machine and connected to the network through the virtual bridge,

wherein the virtual bridge intercepts an ARP request from the virtual machine for querying a MAC address of a target virtual machine, adds a corresponding VDCID to an identification field of the ARP request and redirects the ARP request,

wherein the ARP server queries a corresponding MAC address according to an IP address recorded in a destination IP address field of the ARP request and the corresponding VDCID recorded in the identification field of the ARP request, and transmits the corresponding MAC address in response to the ARP request.

2. The data center network system as claimed in claim 1, wherein the target virtual machine is executed on the physical machine and connected to the network through the virtual bridge,

wherein the virtual bridge determines whether the VDCID of the virtual machine is the same as the VDCID of the target virtual machine according to a virtual machine entry table stored in the virtual bridge,

when the VDCID of the virtual machine is the same as the VDCID of the target virtual machine, the virtual bridge forwards the MAC address of the target virtual machine to the virtual machine according to the virtual machine entry table.

3. The data center network system as claimed in claim 1, wherein the target virtual machine is executed on another physical machine,

wherein the virtual bridge adds the VDCID of the virtual machine to the identification field of the ARP request, and redirects the ARP request to the ARP server,

wherein the ARP server queries the VDCID of the target virtual machine in an address query table, and determines whether a value recorded in the identification field of the ARP request is the same as the VDCID of the target virtual machine,

wherein when the value recorded in the identification field of the ARP request is the same as the VDCID of the target virtual machine, the ARP server transmits the MAC address of the target virtual machine to the virtual bridge according to the address query table, and the virtual bridge transmits the MAC address of the target virtual machine to the virtual machine in response to the ARP request.

4. The data center network system as claimed in claim 1, further a target service node connected to the network.

5. The data center network system as claimed in claim 4,

wherein the virtual bridge intercepts another ARP request from the virtual machine for querying a MAC address of the target service node, adds a predetermined value to an identification field of the another ARP request and redirects the another ARP request to the ARP server,

the ARP server queries the MAC address of the target service node in an address query table according to the identification field and a destination IP address field of the another ARP request, and transmits the MAC address of the target service node to the virtual bridge,

wherein the virtual bridge transmits the MAC address of the target service node to the virtual machine in response to the another ARP request.

6. The data center network system as claimed in claim 4, further comprises a service node connected to the network through the virtual bridge,

wherein the service node broadcasts another ARP request for querying the MAC address of the target service node,

wherein the virtual bridge intercepts the another ARP request, and adds a predetermined value to an identification field of the another ARP request, and redirects the another ARP request to the ARP server,

wherein the ARP server queries the MAC address of the target service node in an address query table according to the identification field and a destination IP address field of the another ARP request, and transmits the MAC address of the target service node to the virtual bridge,

wherein the virtual bridge transmits the MAC address of the target service node to the service node in response to the another ARP request.

7. The data center network system as claimed in claim 1, further comprises a service node having a wrapper module and connected to the network,

wherein the service node broadcasts another ARP request for querying the MAC address of the target virtual machine, wherein the wrapper module adds the VDCID of the target virtual machine to an identification field of the another ARP request,

wherein the ARP server queries the MAC address of the target virtual machine in an address query table according to the identification field and a destination IP address field of the fourth ARP request, and transmits the MAC address of the target virtual machine to the service node in response to the another ARP request.

8. The data center network system as claimed in claim 5,

wherein when the target service node receives a data packet from the virtual machine, the target service node records the private IP address and the MAC address of the virtual machine in a connection mapping table according to a source IP address, a source port, a destination IP address, a destination port and a MAC address of the data packet,

wherein the target service node queries the private IP address and the MAC address of the virtual machine according to the connection mapping table, and transmits a response data packet to the virtual machine according to the private IP address and the MAC address of the virtual machine.

9. The data center network system as claimed in claim 1, further a server load balance (SLB) node having a load balance mapping table and connected to the network,

wherein the SLB node receives a data packet to be transmitted to the virtual machine from an external link, and the SLB node queries the private IP address and the VDCID of the virtual machine according to the load balance mapping table,

wherein the SLB node broadcasts another ARP request for querying the MAC address of the virtual machine, wherein a destination IP address field of the another ARP request records the private IP address of the virtual machine, and an identification field of the another ARP request records the VDCID of the virtual machine,

wherein the ARP server queries the MAC address of the virtual machine in the address query table according to the identification field and the destination IP address field of the another ARP request, and transmits the MAC address of the virtual machine to the SLB node.

10. A data center network system, comprising:

a first physical machine, connected to a network;

a virtual bridge, executed on the first physical machine and connected to the network; and

an address resolution protocol (ARP) server, connected to the network,

wherein the virtual bridge intercepts an address resolution protocol (ARP) request having an identification field and a destination IP address field, adds a corresponding virtual data center identification (VDCID) to the identification field of the ARP request and redirects the ARP request to the ARP server,

wherein the ARP server queries a corresponding MAC address according to an IP address recorded in the destination IP address field of the ARP request and the corresponding VDCID recorded in the identification field of the ARP request, and transmits the corresponding MAC address in response to the ARP request.

11. The data center network system as claimed in claim 10, further comprising:

a plurality of virtual machines, wherein each of the virtual machines has a private Internet protocol (IP) address, a virtual data center identification (VDCID) and a media access control (MAC) address, and the virtual machines are respectively belonged to a plurality of virtual data centers (VDCs), and the virtual machines belonged to the same VDC have the same VDCID;

wherein a first virtual machine and a second virtual machine in the virtual machines are executed on the first physical machine and are connected to the network through the virtual bridge,

wherein the virtual bridge has a virtual machine entry table corresponding to the first physical machine, the virtual machine entry table stores a plurality of entries, and a first entry in the entries records the private IP address, the VDCID and the MAC address of the first virtual machine, and a second entry in the entries records the private IP address, the VDCID and the MAC address of the second virtual machine,

wherein the first virtual machine broadcasts a first address resolution protocol (ARP) request for querying the MAC address of the second virtual machine, wherein a destination IP address field of the first ARP request records the private IP address of the second virtual machine,

wherein the virtual bridge intercepts the first ARP request and determines whether the VDCID of the first virtual machine is the same as the VDCID of the second virtual machine according to the virtual machine entry table corresponding to the first physical machine,

when the VDCID of the first virtual machine is the same as the VDCID of the second virtual machine, the virtual bridge forwards the MAC address of the second virtual machine to the first virtual machine according to the virtual machine entry table corresponding to the first physical machine in response to the first ARP request.

12. The data center network system as claimed in claim 10, further comprising:

a plurality of virtual machines, wherein each of the virtual machines has a private Internet protocol (IP) address, a virtual data center identification (VDCID) and a media access control (MAC) address, and the virtual machines are respectively belonged to a plurality of virtual data centers (VDCs), and the virtual machines belonged to the same VDC have the same VDCID; and

a second physical machine, connected to the network,

wherein a first virtual machine in the virtual machines is executed on the first physical machine and are connected to the network through the virtual bridge,

wherein a third virtual machine in the virtual machines is executed on the second physical machine,

wherein the ARP server maintains an address query table, the address query table stores a plurality of mappings, and the mappings of the address query table record the private IP address, the VDCID and the MAC address of each of the virtual machines,

wherein the first virtual machine broadcasts a second ARP request for querying the MAC address of the third virtual machine, wherein a destination IP address field of the second ARP request records the private IP address of the third virtual machine,

wherein the virtual bridge intercepts the second ARP request, and adds the VDCID of the first virtual machine to an identification field of the second ARP request according to the virtual machine entry table corresponding to the first physical machine, and redirects the second ARP request to the ARP server,

wherein the ARP server queries the VDCID of the third virtual machine in the address query table according to the private IP address of the third virtual machine, and determines whether a value recorded in the identification field of the second ARP request is the same as the VDCID of the third virtual machine,

wherein when the value recorded in the identification field of the second ARP request is the same as the VDCID of the third virtual machine, the ARP server transmits the MAC address of the third virtual machine to the virtual bridge according to the address query table, and the virtual bridge transmits the MAC address of the third virtual machine to the first virtual machine to respond the second ARP request.

13. The data center network system as claimed in claim 10, further comprising:

a plurality of service nodes, connected to the network, wherein each of the service nodes has a service IP address, a VDCID and a MAC address, and the VDCID of each of the service nodes is set to a same predetermined value,

wherein the service nodes comprise a first service node and a second service node, and the first service node is executed on the first physical machine and is connected to the network through the virtual bridge,

wherein the ARP server maintains an address query table, the address query table stores a plurality of mappings, and the mappings of the address query table record the service IP address, the VDCID and the MAC address of each of the service nodes,

wherein the first service node broadcasts a third ARP request for querying the MAC address of the second service node, wherein a destination IP address field of the third ARP request records the service IP address of the second service node,

wherein the virtual bridge intercepts the third ARP request, and adds the predetermined value to an identification field of the third ARP request according to the service IP address of the second service node, and redirects the third ARP request to the ARP server,

wherein the ARP server queries the MAC address of the second service node in the address query table according to the identification field and the destination IP address field of the third ARP request, and transmits the MAC address of the second service node to the virtual bridge,

wherein the virtual bridge transmits the MAC address of the second service node to the first service node in response to the third ARP request.

14. The data center network system as claimed in claim 10, further comprising:

a plurality of virtual machines, wherein each of the virtual machines has a private Internet protocol (IP) address, a virtual data center identification (VDCID) and a media access control (MAC) address, and the virtual machines are respectively belonged to a plurality of virtual data centers (VDCs), and the virtual machines belonged to the same VDC have the same VDCID; and

a third service node, connected to the network and having a wrapper module,

wherein the ARP server maintains an address query table, the address query table stores a plurality of mappings, and the mappings of the address query table record the private IP address, the VDCID and the MAC address of each of the virtual machines,

wherein the third service node broadcasts a fourth ARP request for querying the MAC address of a third virtual machine in the virtual machines, wherein a destination IP address field of the fourth ARP request records the private IP address of the third virtual machine, and the wrapper module adds the VDCID of the third virtual machine to an identification field of the fourth ARP request,

wherein the ARP server queries the MAC address of the third virtual machine in the address query table according to the identification field and the destination IP address field of the fourth ARP request, and transmits the MAC address of the third virtual machine to the third service node to respond the fourth ARP request.

15. The data center network system as claimed in claim 10, further comprising:

a plurality of virtual machines, wherein each of the virtual machines has a private Internet protocol (IP) address, a virtual data center identification (VDCID) and a media access control (MAC) address, and the virtual machines are respectively belonged to a plurality of virtual data centers (VDCs), and the virtual machines belonged to the same VDC have the same VDCID; and

a fourth service node, connected to the network,

wherein the ARP server maintains an address query table, the address query table stores a plurality of mappings, and the mappings of the address query table record the private IP address, the VDCID and the MAC address of each of the virtual machines,

wherein the mappings of the address query table further record a service IP address, a VDCID and a MAC address of the fourth service node, and the VDCID of the fourth service node is set to a predetermined value,

wherein a first virtual machine in the virtual machines is executed on the first physical machine and are connected to the network through the virtual bridge,

wherein the first virtual machine broadcasts a fifth ARP request for querying the MAC address of the fourth service node, where a destination IP address field of the fifth ARP request records the service IP address of the fourth service node,

wherein the virtual bridge intercepts the fifth ARP request, and adds the predetermined value to an identification field of the fifth ARP request according to the service IP address of the fourth service node, and then redirects the fifth ARP request to the ARP server,

the ARP server queries the MAC address of the fourth service node in the address query table according to the identification field and the destination IP address field of the fifth ARP request, and transmits the MAC address of the fourth service node to the virtual bridge,

wherein the virtual bridge transmits the MAC address of the fourth service node to the first virtual machine to respond the fifth ARP request.

16. The data center network system as claimed in claim 15,

wherein when the fourth service node receives a data packet from the first virtual machine, the fourth service node records the private IP address and the MAC address of the first virtual machine in a connection mapping table according to a source IP address, a source port, a destination IP address, a destination port and a MAC address of the data packet,

wherein the fourth service node queries the private IP address and the MAC address of the first virtual machine according to the connection mapping table, and transmits a response data packet to the first virtual machine according to the private IP address and the MAC address of the first virtual machine.

17. The data center network system as claimed in claim 10, further comprising:

a plurality of virtual machines, wherein each of the virtual machines has a private Internet protocol (IP) address, a virtual data center identification (VDCID) and a media access control (MAC) address, and the virtual machines are respectively belonged to a plurality of virtual data centers (VDCs), and the virtual machines belonged to the same VDC have the same VDCID; and

a server load balance (SLB) node, connected to the network, and having a load balance mapping table, wherein the load balance mapping table stores a plurality of mappings, and the mappings of the load balance mapping table record the private IP address and the VDCID of each of the virtual machines,

wherein the ARP server maintains an address query table, the address query table stores a plurality of mappings, and the mappings of the address query table record the private IP address, the VDCID and the MAC address of each of the virtual machines,

wherein the SLB node receives a data packet to be transmitted to a first virtual machine in the virtual machines from an external link, and the SLB node queries the private IP address and the VDCID of the first virtual machine according to the load balance mapping table,

wherein the SLB node broadcasts a sixth ARP request for querying the MAC address of the first virtual machine, wherein a destination IP address field of the sixth ARP request records the private IP address of the first virtual machine, and an identification field of the sixth ARP request records the VDCID of the first virtual machine,

wherein the ARP server queries the MAC address of the first virtual machine in the address query table according to the identification field and the destination IP address field of the sixth ARP request, and transmits the MAC address of the first virtual machine to the SLB node.

18. A virtual bridge, executed on a first physical machine, and connected to a network, comprising:

a receiving module, intercepting a first address resolution protocol (ARP) request, wherein a first virtual machine executed on the first physical machine broadcasts the first ARP request for querying a MAC address of a second virtual machine executed on the first physical machine;

an identification module, coupled to the receiving module, and configured for determining whether a virtual data center identification (VDCID) of the first virtual machine is the same as a VDCID of the second virtual machine; and

a transmitting module, coupled to the identification module,

wherein when the identification module determines the VDCID of the first virtual machine is the same as the VDCID of the second virtual machine, the transmitting module forwards a MAC address of the second virtual machine to the first virtual machine in response to the first ARP request.

19. The virtual bridge as claimed in claim 18, further comprising an entry table maintaining module configured for maintaining a virtual machine entry table of the first physical machine,

wherein the virtual machine entry table includes a plurality of entries,

wherein a plurality of virtual machines executed on the first physical machine and the entry table maintaining module records a private Internet protocol (IP) address, a virtual data center identification (VDCID) and a media access control (MAC) address of each of the virtual machines in the entries.

20. The virtual bridge as claimed in claim 18, further comprising a redirecting module coupled to the transmitting module,

wherein the receiving module intercepts a second ARP request,

wherein the first virtual machine broadcasts the second ARP request for querying a MAC address of a third virtual machine executed on a second physical machine, further comprising:

the redirecting module adds the VDCID of the first virtual machine to an identification field of the second ARP request and redirecting the second ARP request to an ARP server.

21. The virtual bridge as claimed in claim 18, further comprising a redirecting module coupled to the transmitting module,

wherein the receiving module intercepts a third ARP request,

wherein a first service node executed on the first physical machine broadcasts the third ARP request for querying a MAC address of a second service node,

wherein the redirecting module adds a predetermined value to an identification field of the third ARP request, and redirects the third ARP request to an ARP server.

22. The virtual bridge as claimed in claim 18, further comprising a redirecting module coupled to the transmitting module,

wherein the receiving module intercepts a fifth ARP request,

wherein the first virtual machine broadcasts the fifth ARP request for querying a MAC address of a fourth service node,

wherein the redirecting module adds a predetermined value to an identification field of the fifth ARP request, and redirects the fifth ARP request to an ARP server.

23. An address resolution protocol (ARP) server, comprising:

a receiving module, receiving an ARP request having a destination IP address field and an identification field;

an address query table maintaining module, coupled to the receiving module, maintaining an address query table and querying a corresponding MAC address in the address query table according to a IP address recorded in the destination IP address field of the ARP request and a VDCID recorded in the identification field of the ARP request; and

a transmitting module, coupled to the address query table maintaining module and the receiving module, and transmitting the corresponding MAC address in response to the ARP request.

24. The address resolution protocol server as claimed in claim 23, wherein the address query table maintaining module stores a plurality of mappings in the address query table, and records a private IP address, a VDCID and a MAC address of each of a plurality of virtual machines in the mappings.

25. A packet forwarding method for a data center network system, wherein the data center network system comprises a first physical machine and a plurality of virtual machines and a virtual bridge executed on the first physical machine, a first virtual machine and a second virtual machine in the virtual machines are executed on the first physical machine and are connected to a network through the virtual bridge, and each of the virtual machines has a private Internet protocol (IP) address, a virtual data center identification (VDCID) and a media access control (MAC) address, wherein the virtual machines are respectively belonged to a plurality of virtual data centers (VDCs), and the virtual machines belonged to the same VDC have the same VDCID, wherein the virtual bridge has a virtual machine entry table corresponding to the first physical machine, and the virtual machine entry table stores a plurality of entries, the packet forwarding method comprising:

recording the private IP address, the VDCID and the MAC address of the first virtual machine to a first entry in the entries, and recording the private IP address, the VDCID and the MAC address of the second virtual machine to a second entry in the entries;

broadcasting a first address resolution protocol (ARP) request by using the first virtual machine for querying the MAC address of the second virtual machine, wherein a destination IP address field of the first ARP request records the private IP address of the second virtual machine;

intercepting the first ARP request by using the virtual bridge, and determining whether the VDCID of the first virtual machine is the same as the VDCID of the second virtual machine according to the virtual machine entry table corresponding to the first physical machine; and

when the VDCID of the first virtual machine is the same as the VDCID of the second virtual machine, forwarding the MAC address of the second virtual machine to the first virtual machine according to the virtual machine entry table corresponding to the first physical machine by using the virtual bridge in response to the first ARP request.

26. The packet forwarding method of the data center network system as claimed in claim 25, wherein the data center network system further comprises an ARP server connected to the network and a second physical machine, wherein the ARP server maintains an address query table, the address query table stores a plurality of mappings, and the mappings of the address query table record the private IP address, the VDCID and the MAC address of each of the virtual machines, wherein a third virtual machine in the virtual machines is executed on the second physical machine, and the packet forwarding method further comprises:

broadcasting a second ARP request by using the first virtual machine for querying the MAC address of the third virtual machine, wherein a destination IP address field of the second ARP request records the private IP address of the third virtual machine;

intercepting the second ARP request by using the virtual bridge, adding the VDCID of the first virtual machine to an identification field of the second ARP request according to the virtual machine entry table corresponding to the first physical machine, and redirecting the second ARP request to the ARP server;

querying the VDCID of the third virtual machine in the address query table according to the private IP address of the third virtual machine by using the ARP server, and determining whether a value recorded in the identification field of the second ARP request is the same as the VDCID of the third virtual machine; and

when the value recorded in the identification field of the second ARP request is the same as the VDCID of the third virtual machine, the ARP server transmitting the MAC address of the third virtual machine to the virtual bridge according to the address query table, and the virtual bridge transmitting the MAC address of the third virtual machine to the first virtual machine to respond the second ARP request.

27. The packet forwarding method of the data center network system as claimed in claim 26, wherein the data center network system further comprises a plurality of service nodes connected to the network, wherein each of the service nodes has a service IP address, a VDCID and a MAC address respectively recorded in the mappings of the address query table of the ARP server, wherein the VDCID of each of the service nodes is set to a same predetermined value, wherein the service nodes comprise a first service node and a second service node, and the first service node is executed on the first physical machine and is connected to the network through the virtual bridge, and the packet forwarding method further comprises:

broadcasting a third ARP request by using the first service node for querying the MAC address of the second service node, wherein a destination IP address field of the third ARP request records the service IP address of the second service node;

intercepting the third ARP request by using the virtual bridge, adding the predetermined value to an identification field of the third ARP request according to the service IP address of the second service node, and redirecting the third ARP request to the ARP server;

querying the MAC address of the second service node in the address query table according to the identification field and the destination IP address field of the third ARP request by using the ARP server, and transmitting the MAC address of the second service node to the virtual bridge; and

transmitting the MAC address of the second service node to the first service node by using the virtual bridge in response to the third ARP request.

28. The packet forwarding method of the data center network system as claimed in claim 26, wherein the data center network system further comprises a third service node connected to the network and having a wrapper module, and the packet forwarding method further comprises:

broadcasting a fourth ARP request by using the third service node for querying the MAC address of the third virtual machine, wherein a destination IP address field of the fourth ARP request records the private IP address of the third virtual machine, and the wrapper module adds the VDCID of the third virtual machine to an identification field of the fourth ARP request; and

querying the MAC address of the third virtual machine in the address query table according to the identification field and the destination IP address field of the fourth ARP request by using the ARP server, and transmitting the MAC address of the third virtual machine to the third service node to respond the fourth ARP request.

29. The packet forwarding method of the data center network system as claimed in claim 26, wherein the data center network system further comprises a fourth service node connected to the network, and the packet forwarding method further comprises:

recording a service IP address, a VDCID and a MAC address of the fourth service node to the mappings of the address query table, and setting the VDCID of the fourth service node to a predetermined value;

broadcasting a fifth ARP request by using the first virtual machine for querying the MAC address of the fourth service node, where a destination IP address field of the fifth ARP request records the service IP address of the fourth service node;

intercepting the fifth ARP request by using the virtual bridge, adding the predetermined value to an identification field of the fifth ARP request according to the service IP address of the fourth service node, and redirecting the fifth ARP request to the ARP server,

querying the MAC address of the fourth service node in the address query table according to the identification field and the destination IP address field of the fifth ARP request by using the ARP server, and transmitting the MAC address of the fourth service node to the virtual bridge; and

transmitting the MAC address of the fourth service node to the first virtual machine by using the virtual bridge in response to the fifth ARP request.

30. The packet forwarding method of the data center network system as claimed in claim 29, further comprising:

when the fourth service node receives a data packet from the first virtual machine, recording the private IP address and the MAC address of the first virtual machine in a connection mapping table according to a source IP address, a source port, a destination IP address, a destination port and a MAC address of the data packet by using the fourth service node; and

querying the private IP address and the MAC address of the first virtual machine according to the connection mapping table by using the fourth service node, and transmitting a response data packet to the first virtual machine according to the private IP address and the MAC address of the first virtual machine.

31. The packet forwarding method of the data center network system as claimed in claim 26, wherein the data center network system further comprises a server load balance (SLB) node connected to the network, wherein the SLB node has a load balance mapping table, the load balance mapping table stores a plurality of mappings, and the mappings of the load balance mapping table record the private IP address and the VDCID of each of the virtual machines, and the packet forwarding method comprises:

receiving a data packet to be transmitted to the first virtual machine from an external link by using the SLB node, and querying the private IP address and the VDCID of the first virtual machine according to the load balance mapping table by using the SLB node;

broadcasting a sixth ARP request by using the SLB node for querying the MAC address of the first virtual machine, wherein a destination IP address field of the sixth ARP request records the private IP address of the first virtual machine, and an identification field of the sixth ARP request records the VDCID of the first virtual machine; and

querying the MAC address of the first virtual machine in the address query table according to the identification field and the destination IP address field of the sixth ARP request by using the ARP server, and transmitting the MAC address of the first virtual machine to the SLB node.