Patent Publication Number: US-2007101323-A1

Title: Automatic virtual machine adjustments to network changes

Description:
BACKGROUND  
      Emulator software programs allow an application for use in one platform to be used on a machine running another platform. This allows computing systems (e.g., a host machine) to run applications for more than one platform. A host machine implements a host environment. The host environment is associated with the operating system. An emulator application running in the host environment emulates a guest environment. A guest operating system can be installed on the guest environment. Once the guest operating system is installed, applications configured to run in the guest environment may ultimately be executed on the host machine.  
      For example, emulator software may emulate personal computer (PC) hardware. The emulated PC hardware may include a CPU, memory, hard drives, a network interface card (NIC), and other typical hardware devices. Thus, the emulator software emulates these devices by creating virtual devices (e.g., a virtual network interface card). To a guest operating system running in the emulated environment, the NIC may appear to be a standard Ethernet network interface card; however, it is actually a virtual network interface card. The emulator software may route packets from a live network to the virtual network interface card and from the virtual network interface card to the live network. This allows a guest operating system (e.g., an operating system running on top of the emulator software) to connect to a network and software running on the guest operating system to interact with the network. For example, a guest operating system may allow an entity to print to a network printer, access a file server, and browse the World Wide Web through emulated PC hardware having an emulated NIC.  
      Emulator software may provide different networking options for a guest environment. In one case, a guest operating system may share an IP address through an emulated network address translator (NAT). A NAT is used to map one or more outside network IP addresses into one or more internal network IP addresses. In this mode, sometimes called a shared IP mode, minimal configuration of the guest operating system is required. The configuration settings which allow the guest operating system to connect with the network are provided by an emulated DHCP service.  
      In another case, a guest operating system may have a virtual direct connection with a live network. In this mode, sometimes called a direct networking mode, the guest operating system has a network IP address independent of the host operating system. In order to connect with the live network, the guest operating system itself is configured with IP network configuration information. The information may come from a DHCP server or require manual input from a user.  
      Previous emulator applications provide networking capability between a guest environment on a host machine and a single live network. However, the host machine may switch network environments (e.g., a laptop computer with wireless networking capability may move from a first network to new network). When this happens, the emulator software and guest operating system may not recognize the change in the networking environment. Thus, guest environment networking fails because the guest environment is attempting to communicate with a new network using network configuration settings for an old network. Typically, even in scenarios where the network settings are available automatically, a user must prompt the guest operating system to query for updated network information.  
     SUMMARY  
      The technology described herein pertains to virtual machine software that adjusts networking configuration information in a guest environment in response to detecting changes in a networking environment. Virtual machine software may include emulation software, virtualization software, and other software that constructs and runs a virtual machine. In one embodiment, the changes in the networking environment are detected through updated network configuration settings for a host operating system. In response to detecting the change, the virtual machine software initiates a reconfiguration of virtual machine network configuration settings, guest operating system network configuration settings, or both. This allows network connectivity for the guest operating system to be restored without user interaction.  
      In one embodiment, network configuration settings for a guest environment which shares a network address with a host operating system are changed. In particular, network configuration settings configured at a network address translation (NAT) module are changed. In another embodiment, network configuration settings for a guest environment having a virtual direct network connection are changed. In this case, the network configuration settings are changed within the guest operating system. In other embodiments, settings within a NAT, operating system and optionally other modules may be changed. The updated network configuration settings may be retrieved from a host operating system, the network, local memory or some other source. Network configuration settings for a new network may be saved in memory, secondary storage or some other location and recalled when the host machine attempts to connect to the network in the future.  
      This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates an embodiment of a system for providing a network connection to a guest environment.  
       FIG. 2  illustrates an embodiment of a computing environment for implementing the present technology.  
       FIG. 3  illustrates a block diagram of an embodiment of a host machine having a guest environment that shares an IP address.  
       FIG. 4  illustrates a block diagram of an embodiment of a host machine having a guest environment with a virtual direct networking connection.  
       FIG. 5  illustrates a flowchart for an embodiment of configuring guest environment network settings.  
       FIG. 6  illustrates a flowchart of an embodiment for accessing updated host network configuration settings.  
       FIG. 7  illustrates a flowchart of an embodiment for configuring network configuration settings for a virtual machine.  
       FIG. 8  illustrates a flowchart of an embodiment for configuring network configuration settings for a guest operating system.  
    
    
     DETAILED DESCRIPTION  
      The technology described below pertains to virtual machine software that adjusts networking configuration information for a guest environment in response to detecting changes in a networking environment. In one embodiment, the changes in the networking environment are detected through updated network configuration settings for a host operating system. After detecting a change, the virtual machine software initiates reconfiguration of the emulation software network configuration settings, the virtual machine network configuration settings, guest operating system network configuration settings, or any combination of the three. The reconfiguration allows network connectivity for the guest operating system to be restored without user interaction.  
      Network configuration settings for a guest environment can be reconfigured for a shared network IP address, a virtual direct connection and other configurations. For a shared network IP address, some network configuration settings for a guest environment can be configured at a network address translation (NAT) module; additional network configuration settings can be changed within the guest operating system. For a virtual direct network connection, network configuration settings for a guest environment can be changed within the guest operating system. The updated network configuration settings may be retrieved from a host operating system, the network, local memory or some other source. Network settings for a new network may be saved in memory and recalled when the host machine attempts to reconnect to the same network in the future. This is discussed in more detail below.  
      The software used to implement the present technology may be either emulation software, virtualization software or some other type of software (hereinafter referred to as “virtual machine software”). In particular, virtual machine software may construct and run one or more virtual machines, and thus may implement the features of the technology discussed herein. The virtual machine software used to implement the present invention may be a software application, part of a host operating system, an extension to a host operating system or some other computer code able to construct and run one or more virtual machines. Thus, although virtual machine software may be referred to herein as a virtual machine application, it is understood that a host operating system or extension thereto may be used to implement virtual machine software. References to a virtual machine applications are intended to include other types of code (such as operating systems and their extensions) in addition to software applications.  
      Virtual machine software implemented by emulation software may create a virtual environment entirely through software. Thus, the software may translate CPU instructions, create emulated hardware devices, and perform other functions. Emulation software may operate by presenting an entirely different set of hardware to the virtual machine. For example, emulation software may run Windows x86 software on a PowerPC based Macintosh.  
      Virtual machine software implemented by virtualization software may create a virtual environment that matches the host hardware. For instance, virtualization software may run Linux x86 software within a virtual machine hosted on an x86 based Windows virtual machine that runs “Windows XP” operating system software, by Microsoft Corporation of Redmond Wash. In some cases, virtualization software may include some emulation. For example, virtualization software may provide a virtual machine that has the same processor as the host, and some code within the virtual machine may be run directly. However, many of the devices present within the virtual environment can be emulated, such as a video card, network interface card, or other devices.  
      Adjusting network configuration settings for a guest environment may include setting IP network configuration information associated with a new network. IP network configuration information may include an internet protocol (IP) address, a domain name server or service (DNS) address, a router gateway address, and other information associated with a network connection. An IP address is a number that identifies a sender or receiver of information (e.g., a host machine) that is sent in packets across the Internet. Under internet protocol version 4, an IP address is a thirty-two bit number written as four eight-bit numbers separated by dots. A DNS address is an address associated with a server or service that translates domain names (alphanumeric names associated with a network location) into IP addresses. The router gateway address is the IP address associated with the location of the router for the current network. That is, the IP address where the current network and one or more additional networks meet (the “gateway” for the networks). Additionally, adjusting network configuration settings may include changing settings related to DHCP information and other information associated with a network. For example, a setting may be saved which indicates whether a DHCP service within a NAT is to be used.  
       FIG. 1  illustrates an embodiment of a system for providing a network connection to a guest environment. The system of  FIG. 1  includes a host computer  100 , network connection A  120 , network connection B  130 , network  140 , and network servers  150 - 170 . Network connections  120 - 130  allow a computing system, such as host machine  100 , to connect with network servers  150 - 170  over network  140 . In one embodiment, network  140  may be implemented as the Internet.  
      Host machine  100  may include host operating system  116 , virtual machine software  114  and virtual machine  112 . In one embodiment, virtual machine software  114  may run on host operating system  116 . While running on host operating system  116 , virtual machine software  114  may provide virtual machine  112 . In one embodiment, a guest environment may be comprised of virtual machine software  114 , virtual machine  112 , and other code (not illustrated).  
      In some embodiments, host machine  100  may have access to more than one network. For instance, host machine  100  may be implemented as a mobile device, such as a laptop computer, PDA, or other mobile computing device, that can physically be moved within range of different wireless networks. In this case, host machine  100  may first be configured to connect to network  140  through network connection A  120 . For instance, network connection  120  may be a network connection at a user&#39;s home. As illustrated by the dotted line, host machine  100  may be moved to a different location (indicated by the dashed-line box  135 ) or otherwise set to connect with network  140  through network connection B  130 . For example, after accessing the Internet from home, the user may bring host machine  100  to work and attempt to connect to the Internet from a work network connection. The present technology detects the change in the networking environment for host machine  100  and changes the guest environment network configuration settings from those associated with the network connection A to those associated with network connection B.  
       FIG. 2  illustrates an example of a suitable computing system environment  200  on which the present technology may be implemented. The computing system environment  200  is only one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing environment  200  be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment  200 . In one embodiment, the computing environment of  FIG. 2  may be used to implement host machine  100  of  FIG. 1 .  
      The invention is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well known computing systems, environments, and/or configurations that may be suitable for use with the invention include, but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like.  
      The invention may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.  
      With reference to  FIG. 2 , an exemplary system for implementing the invention includes a general purpose computing device in the form of a computer  210 . Components of computer  210  may include, but are not limited to, a processing unit  220 , a system memory  230 , and a system bus  221  that couples various system components including the system memory to the processing unit  220 . The system bus  221  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus.  
      Computer  210  typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer  210  and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by computer  210 . Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of the any of the above should also be included within the scope of computer readable media.  
      The system memory  230  includes computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM)  231  and random access memory (RAM)  232 . A basic input/output system  233  (BIOS), containing the basic routines that help to transfer information between elements within computer  210 , such as during start-up, is typically stored in ROM  231 . RAM  232  typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit  220 . By way of example, and not limitation,  FIG. 2  illustrates operating system  234 , application programs  235 , other program modules  236 , and program data  237 .  
      The computer  210  may also include other removable/non-removable, volatile/nonvolatile computer storage media. By way of example only,  FIG. 2  illustrates a hard disk drive  240  that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive  251  that reads from or writes to a removable, nonvolatile magnetic disk  252 , and an optical disk drive  255  that reads from or writes to a removable, nonvolatile optical disk  256  such as a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive  241  is typically connected to the system bus  221  through a non-removable memory interface such as interface  240 , and magnetic disk drive  251  and optical disk drive  255  are typically connected to the system bus  221  by a removable memory interface, such as interface  250 .  
      The drives and their associated computer storage media discussed above and illustrated in  FIG. 2 , provide storage of computer readable instructions, data structures, program modules and other data for the computer  210 . In  FIG. 2 , for example, hard disk drive  241  is illustrated as storing operating system  244 , application programs  245 , other program modules  246 , and program data  247 . Note that these components can either be the same as or different from operating system  234 , application programs  235 , other program modules  236 , and program data  237 . Operating system  244 , application programs  245 , other program modules  246 , and program data  247  are given different numbers here to illustrate that, at a minimum, they are different copies. A user may enter commands and information into the computer  20  through input devices such as a keyboard  262  and pointing device  261 , commonly referred to as a mouse, trackball or touch pad. Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit  220  through a user input interface  260  that is coupled to the system bus, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor  291  or other type of display device is also connected to the system bus  221  via an interface, such as a video interface  290 . In addition to the monitor, computers may also include other peripheral output devices such as speakers  297  and printer  296 , which may be connected through an output peripheral interface  290 .  
      The computer  210  may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer  280 . The remote computer  280  may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer  210 , although only a memory storage device  281  has been illustrated in  FIG. 2 . The logical connections depicted in  FIG. 2  include a local area network (LAN)  271  and a wide area network (WAN)  273 , but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet.  
      When used in a LAN networking environment, the computer  210  is connected to the LAN  271  through a network interface or adapter  270 . When used in a WAN networking environment, the computer  210  typically includes a modem  272  or other means for establishing communications over the WAN  273 , such as the Internet. The modem  272 , which may be internal or external, may be connected to the system bus  221  via the user input interface  260 , or other appropriate mechanism. In a networked environment, program modules depicted relative to the computer  210 , or portions thereof, may be stored in the remote memory storage device. By way of example, and not limitation,  FIG. 2  illustrates remote application programs  285  as residing on memory device  281 . It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used.  
      As discussed above, a guest environment may be configured to network through a shared network IP address or a virtual direct connection.  FIG. 3  illustrates a block diagram of an embodiment of host machine having a guest environment that shares a network IP address. The block diagram of  FIG. 3  includes network connection A  120 , network connection B  130 , and host machine  100 .  
      Host machine  100  may first access a network through network connection  120 . Network connection  120  may be a user&#39;s home network connection, a connection provided by a coffee shop or an internet café or some other network connection. The network environment may then change from network connection  120  to network connection  130 . The new network connection may be the user&#39;s work, an airport, a library or some other network connection other than network connection  120 . When the change occurs, network configuration settings associated with network connection  130  are needed in order to network through the new connection.  
      In one embodiment wherein the network is the Internet, a network connection may include a physical or wireless connection to an Internet Service Provider (ISP). The ISP allows devices to connect to a network using a network connection provided by the ISP. The network connection may include a DSL connection, dial-up connection, Ti connection or some other connection from the host machine to the ISP. The ISP then transmits data packets between the host machine and other devices over the Internet.  
      Host machine  100  includes host operating system  116 , virtual machine software  114 , virtual machine  112 , NAT  320 , guest operating system  330 , and guest operating system application  340 . In one embodiment, host machine  100 , host operating system  116 , virtual machine software  114  and virtual machine  112  of  FIG. 3  may be the same as those illustrated in  FIG. 1 . In one embodiment, a guest environment within host machine  100  of  FIG. 3  may include virtual machine software  114 , emulated hardware provided by virtual machine software  114 , virtual machine  112  and guest operating system  330 .  
      Host operating system  116  may communicate with network connections  120 - 130 , virtual machine software  114  and the hardware that it may emulate, and virtual machine  112 . Host operating system  116  includes host operating system IP network configuration information  118 . Host network information  118  is configured by host operating system  116  and is associated with the network connection that the host operating system is currently using or last used. In one embodiment, host operating system  116  may be implemented with “Mac OS X” software, by Apple Computer, Incorporated of Cupertino, Calif. In other embodiments, host operating system  116  can be implemented as another operating system platform, including Linux, Windows operating system, and other systems.  
      Virtual machine software  114  may send and receive information with host operating system  116  and guest operating system  330 . In one embodiment, virtual machine software  114  includes code that implements virtual machine  112 . Virtual machine software  114  may also emulate hardware. The emulated hardware may include NAT  320 , emulated NIC  310  and other hardware (discussed in more detail below). In one embodiment, virtual machine software  114  may be implemented as “Virtual PC for Mac” software, by Microsoft Corporation, of Redmond, Wash.  
      Virtual machine  112  is provided by virtual machine software  114  and may run a guest operating system, a guest operating system application, or other code. Virtual machine  112  may incorporate an emulated network interface card (NIC)  310  and communicate with NAT  320 .  
      Guest operating system  330  may communicate with virtual machine software  114  and run on virtual machine  112 . In one embodiment, operating system  330  may be implemented with “Windows XP Operating System” software, provided by Microsoft Corporation, of Redmond, Wash. Guest operating system  330  may include virtual machine communication code  335 .  
      Guest operating system  330  may also communicate with guest operating system application  340 . Application  340  may be any application or code configured to run on a platform consistent with guest operating system  330 . In some embodiments, application  340  may be a networking application (e.g., a web browser application). In this case, application  340  may communicate through a networking connection established between guest operating system  330  and either of network connections  120 - 130 .  
      Guest operating system  330  may send and receive information with virtual machine software  114  through virtual machine communication code  335 . Virtual machine communication code runs in guest operating system  330  and is aware of and can communicate with virtual machine software  114 . In one embodiment, virtual machine communication code  335 , guest operating system  330  and guest operating system application  340  are conceptually run in the emulated hardware environment (virtual machine  112 ) provided by virtual machine software  114 . This may also be the case for the embodiment illustrated in  FIG. 4 , discussed in more detail below. In one embodiment, virtual machine communication code  335  may be implemented as an extension installed in guest operating system  330 .  
      Guest operating system  330  may send and receive information through network connections  120 - 130 . For example, to transmit information through a network connection, guest operating system  330  may send data to emulated NIC  320 . Emulated NIC  320  receives the data and transmits the data to NAT  320 . NAT  320  receives the data from NIC  320  and sends the data to host operating system  116 . In one embodiment, NAT  320  processes the data before sending it to host operating system  116  to prepare the data to be transmitted through a shared IP address. After receiving the data from NAT  320 , host operating system  116  transmits the data to the network connection. This is discussed in more detail below with respect to  FIG. 5 .  
       FIG. 4  illustrates a block diagram of an embodiment of a host machine having a guest environment with a virtual direct network connection. Unlike the block diagram of  FIG. 3 , the guest environment illustrated in  FIG. 4  has a network IP address independent of a host operating system network IP address. The block diagram of  FIG. 4  includes network connections  120 - 130  in communication with host machine  100 . Host machine  100  of  FIG. 4  includes host operating system  116 , virtual machine software  114 , virtual machine  112 , guest operating system  330  and guest operating system application  340  similar to the host machine of  FIG. 3 . The guest environment of  FIG. 4  includes virtual machine software  114 , virtual machine  112  and guest operating system  330 .  
      Host machine  100  of  FIG. 4  is similar to the host machine illustrated in  FIG. 3 . However, virtual machine  112  of  FIG. 4  communicates with a network connection directly through Ethernet card  117  and does not provide an emulated NAT device. In a guest environment with a virtual direct networking connection, the NAT is not required to map a dynamic IP address for guest operating system  330  into a single shared IP address. Rather, guest operating system  330  sends packets to emulated NIC  310 . Emulated NIC  310  forwards the packets to Ethernet card  117 . Ethernet card  117  then transmits the packets to a network connection. In one embodiment, packets from guest operating system  330  are not processed by host operating system  116 . In some embodiments, data packets can be transmitted to a network using a means other than an Ethernet card, for example using WiFi 802.11 or some other wireless communication means. Operation of the guest environment of  FIG. 4  is discussed in more detail below.  
      As discussed above, when a networking environment for a host machine changes to a new network, the technology described herein may configure a guest environment within the host machine with network configuration settings for the new network.  FIG. 5  illustrates a flow chart of an embodiment for configuring guest environment network configuration settings. In one embodiment, the flow chart of  FIG. 5  provides a methodology for configuring network configuration settings for the guest environments of  FIGS. 3 and 4 . First, a network environment change is detected at step  510 . In one embodiment, the change in the network environment can be detected by host operating system  116  of  FIGS. 3-4 .  
      In an embodiment wherein host operating system  116  is implemented by “Mac OS X” software, the host operating system may include a system configuration framework. The system configuration framework can be configured to send a notification in response to an event detected by the host operating system. One such event may be a change in a networking environment for the host operating system. That is, the operating system may be setup to generate and send a notification in response to detecting a new network connection. Accordingly, virtual machine software  114  may detect the networking environment change by receiving a notification from the host operating system when the network environment changes.  
      In one embodiment, the notification may include IP network configuration information. The notification may also include an identifier associated with the particular IP network configuration information. In this case, the identifier may be a name associated with the network information and assigned by a host operating system naming scheme. For example, if host operating system  116  associates the new network with a name of “home network,” that name may be included in the notification.  
      After detecting a network environment change by virtual machine software  114 , updated host operating system network configuration settings are accessed at step  520 . The updated host network configuration settings may include IP network configuration information for the host. In one embodiment, virtual machine software  114  accesses the updated host network settings. Accessing updated host network settings can be performed in a similar manner for a guest environment sharing an IP address and a guest environment with a virtual direct network connection. Accessing updated host network settings is discussed below in more detail with respect to the flowchart of  FIG. 6 .  
      After the host network configuration settings are accessed, guest environment network configuration settings are configured at step  530 . Guest environment network configuration settings allow guest operating system  330  to access the new or changed live network. Configuring guest environment network configuration settings may differ depending on how a guest environment IP address is utilized. Configuring guest environment network configuration settings for a shared IP address is discussed in more detail below with respect to the flow chart of  FIG. 7 . Configuring guest environment network settings for a virtual direct network connection is discussed in more detail below with respect to the flowchart of  FIG. 8 .  
      After configuring the guest environment network configuration settings at step  530 , the guest environment may communicate over network  140  using the updated network configuration settings at step  540 . In one embodiment, the guest environment of  FIGS. 3-4  may communicate with network servers  150 - 170  of  FIG. 1 . The guest environment may communicate over the network through a shared IP address, a virtual direct networking connection, or some other network connection configuration.  
      In the case of a shared IP address, guest operating system  330  or guest operating system application  340  may send and receive data packets with emulated NIC  310 . Emulated NIC  310  receives the data packets and sends the data packets to NAT  320 . NAT  320  processes the data packets and sends the processed data packets to host operating system  116 . In some embodiments, a NAT adjusts outgoing packets to use the shared IP address. Characteristics of the adjusted packets may be stored so that return packets can be properly routed to the correct client (such as the guest operating system).  
      With respect to  FIG. 3 , host operating system  116  then transmits the stamped data packets through network connection  130 . The data packets may then be transmitted to network servers  150 - 170  over network  140  of  FIG. 1 . A response to the data packets may be sent to host machine  100  by the receiving server of servers  150 - 170 . Once the response data packets are received by host machine  100 , host operating system  116  sends the response packets to NAT  320 . NAT  320  receives the packets and routes the packets to the sender of the original data packets (e.g., the sending guest operating system or guest operating system application).  
      In the case of a virtual direct network connection, guest operating system  330  may send data packets through a virtual direct connection over network  140  to servers  150 - 170 . In this case, guest operating system network connection information is updated to include the new IP address for the virtual machine for the new network connection. With respect to  FIG. 4 , guest environment  330  configures outgoing data packets with the new IP address and sends the packets to emulated NIC  310 . Emulated NIC  310  receives the packets and forwards the packets to Ethernet card  117 . In one embodiment, minimal if any processing is performed on the data packets by NIC  310  and host operating system  116 . The outgoing data packets are then sent through new network connection  130  over network  140 . The data packets may be sent to any device over network  140 , such as network servers  150 - 170 . If the receiving device sends a response, the response is directed towards the new IP address associated with guest operating system  330 . The response packets are received by host machine  100  through Ethernet card  117  and routed to emulated NIC  310 . Emulated NIC  310  then routes the response data packets with the new network IP address directly to guest operating system  330 .  
      As discussed above with respect to  FIG. 5 , after a changed networking environment is detected, updated host IP network configuration information is retrieved.  FIG. 6  illustrates a flowchart of an embodiment for accessing updated host networking information. In one embodiment, the flow chart of  FIG. 6  provides more detail for step  520  of  FIG. 5 . First, virtual machine software  114  retrieves host operating system IP network configuration information from host operating system  116  at step  610 . The IP network configuration information can be retrieved in response to receiving a notification that the networking environment has changed.  
      In one embodiment, virtual machine software  114  sends a request to host operating system  116  for the host network configuration settings. When host operating system  116  is implemented with “Mac OS X” software, a networking communication request may be sent to the system configuration framework of the operating system. In one embodiment, the requested setting information may include host operating system settings for the network internet protocol address, a domain name server or service address, a router gateway address, and other information associated with the network connection used by host operating system  116 . In response to the request from virtual machine software  114 , host operating system  116  retreives and sends the IP network configuration information to virtual machine software  114 . In one embodiment, the system configuration framework processes the request and sends the response to virtual machine software  114 .  
      After the IP network configuration information is retrieved from host operating system  116 , virtual machine software  114  determines whether corresponding guest environment network configuration settings are stored at step  620 . In some instances, host operating system  116  may have connected to the new network connection at a previous time. Accordingly, virtual machine software  114  may have saved the guest environment network configuration settings for the network connection when the previous connection was configured or changed. The saved settings may include the IP network configuration information retrieved from the host, information added by a user, information retrieved from the network by the guest environment and other information.  
      For example, a user may connect a host machine to a network connection provided by an employer. The employer may provide a static IP address from a static IP address pool to employees wishing to access the network. In order to utilize a static IP address, the user may have to obtain the static IP address from an administrator. At some point after a user enters the static IP address into guest operating system  320 , application  114  may store the address as part of the settings associated with the particular network connection. In this case, when the user attempts to reconnect with the network connection, the static IP address used by the user in the previous connection would be recalled along with the other saved settings for the particular connection. The network connection settings may be saved in different ways and at different times. For example, the current network settings may be saved once a new connection is detected. In another instance, the network settings may be saved in response to detecting traffic between the guest operating system and the network connection. In some embodiments, other methods may be used to save the network configuration settings in different ways and at different times in addition to the examples discussed above.  
      In some embodiments, network configuration settings may be retrieved using a tag associated with the settings. The tag may be generated by a user, host operating system  116 , virtual machine software  114 , or some other source. In one embodiment, host operating system  116  generates the tag name and includes the tag name in the notification in response to detecting a changed networking environment. The name may be accessed by virtual machine software  114  from the notification received with respect to step  510  of  FIG. 5  or when the information is accessed at step  610  of  FIG. 6 .  
      In another embodiment, virtual machine software  114  may generate a tag for the networking information using hashing. In this case, the tag may be generated by performing hashing on two or more elements of the networking configuration information into a key. For example, the tag may be generated by hashing the network IP address and the DNS server address. The hash key and corresponding network configuration settings are then stored in a hash table. When a new network is detected, the same elements of the new network are hashed. The hash of the new network is compared to the hashes in the hash table. If a match is found, the network configuration settings associated with the matching hash in the hash table are retrieved (and loaded into the guest environment as discussed below). If a determination is made that network configuration settings corresponding with the new detected network are maintained in storage, flowchart of  FIG. 6  continues to step  630  where stored settings for the guest environment are retrieved. If a determination is made that no corresponding settings are stored in memory, flowchart  600  continues to step  640  where the default network configuration settings may be selected for the guest environment. These default settings may be derived from the host operating system network configuration settings. In this case, the IP network configuration information retrieved by virtual machine software  114  from host operating system  114  at step  610  will be used to configure the network connection settings for the guest environment. Thus, in one embodiment, the internet protocol address, domain name server or service address, router gateway address, and other settings retrieved from host operating system  116  may be used to adjust the settings in the guest environment.  
      After the appropriate network configuration settings have been selected, the guest environment network configuration settings are configured. Guest environment network configuration settings are set differently depending on how the guest environment uses a network IP address.  FIG. 7  illustrates a flowchart of an embodiment for configuring network configuration settings in a guest environment that shares an IP address with a host environment. In this case, the network settings are configured for a virtual machine provided by virtual machine software  114 . In one embodiment, the flow chart of  FIG. 7  provides more detail of step  530  of  FIG. 5 . First, settings in NAT  320  are configured at step  710 . In one embodiment, NAT  320  is configured with the network configuration settings retrieved from the host operating system or from storage. For example, network settings for NAT  320  may be set to the internet protocol address, domain name server or service address, router gateway address, and other settings retrieved from host operating system  116 . NAT  320  may use the network settings to process data packets for guest operating system  330 . For example, since NAT  320  is used in a shared IP address mode, NAT  320  may use the setting information to adjust guest environment  330  networking data packets to be transmitted using the actual IP address assigned to host machine  100 , but may record or associate the data packets with a dynamic IP address associated with guest operating system  330 . In this case, when a response is received by host machine  100 , the response data packets may be routed to virtual NAT  320 . NAT  320  may then restore the dynamic address associated with the guest operating system  330  and then route the response data packets to guest operating system  330 . Since virtual NAT  320  is implemented as software provided by virtual machine software  114 , the settings may be configured by virtual machine software  114 .  
      After settings are configured in NAT  320 , settings in the guest operating system may optionally be configured. In some embodiments, the guest operating system network settings need not be changed in response to a network change where the guest environment shares a network IP address with the host operating system. Network configuration settings are optionally transmitted to virtual machine communication code  335  of guest operating system  330  at step  720 . In response to receiving the settings, virtual machine communication code  335  configures guest operating system  330  with the appropriate network configuration settings at step  730 . The settings received by virtual machine communication code  335  and set in guest operating system  330  may include an internet protocol address assigned to host machine  100 , domain name server or service address used by host machine  100 , router gateway address, a dynamic IP address assigned to the operating system from virtual NAT  320  and other settings. When guest operating system is implemented by “Windows XP Operating System” software, the settings may set as settings for a new and current connection for the operating system. For example, the network IP address for the new network may be set to the dynamic IP address assigned by virtual NAT  320 . The dashed lines comprising the boxes illustrating steps  720  and  730  in the flow chart of  FIG. 7  indicate these steps are optional.  
      NAT  320  configuration settings and any configuration settings for guest operating system  330  are applied at step  740 . That is, the new settings are activated in virtual NAT  320  and guest operating systems  330  so the guest environment may connect to the new network. Next, the guest operating system  330  may optionally retrieve additional connection information at step  750 . In one embodiment, guest operating system  330  may retrieve additional information from the new network connection to complete the network setting configuration. The additional information may include a new DNS server address, updated routing information or other information. The dashed line comprising the box illustrating step  750  indicates this step is optional. Next, the complete set of network configuration settings for the guest environment is stored at step  760 . In one embodiment, the complete network configuration settings include settings for the NAT  320 , guest operating system  330 , and any other guest environment network settings or information associated with the newly detected connection. The network configuration settings may be saved along with a tag associated with settings. The tag may be generated by a host operating system naming scheme, a hashing method or some other method. In one embodiment, the network configuration settings are stored by virtual machine software  114  in a data store directly or indirectly accessible by virtual machine software  114 . As discussed above, in some embodiments the settings may be saved at different times and using different methods.  
      In one embodiment, network configuration settings may be updated for a guest environment having a virtual direct connection.  FIG. 8  illustrates a flowchart of an embodiment for configuring network configuration settings for a guest operating system having a virtual direct connection with a network. In one embodiment, the flow chart of  FIG. 8  provides more detail of step  530  of  FIG. 5 . First, retrieved configuration settings are transmitted to virtual machine communication code  335  of guest operating system  330  at step  810 . The settings transmitted to virtual machine communication code  335  may be those retrieved from memory by virtual machine software  114  or default settings, possibly derived from the host operating system settings.  
      Next, virtual machine communication code  335  configures network configuration settings in guest operating system  330  at step  820 . In this case, the settings that were applied to NAT  320  in  FIG. 7  may be applied to guest operating system  330 . For example, the network settings of an internet protocol address assigned to guest operating system  330 , domain name server or service address used by host machine  100 , router gateway address, and other settings may be set in guest operating system  330 . In particular, the internet protocol address is set to allow guest operating system  330  to send and receive data packets through a virtual direct connection with network  140 . Next, settings in network interface card  210  of virtual machine  112  are optionally configured at step  830 . With respect to  FIG. 4 , guest operating system  330  communicates with a network connection through emulated NIC  210  and Ethernet card  117  of host machine  116 . In cases where emulated NIC  210  will need to be reconfigured for a new network, NIC settings are configured at step  830 . An For example, the NIC may be configured with the new internet protocol address, router gateway address or other networking information in order to transmit data packets between network  140  and guest operating system  330 . The dashed line comprising the box illustrating step  830  indicates this step is optional.  
      The new network configuration settings in guest operating system  330  and NIC  210  are applied at step  840 . Application of the settings in guest operating system  330  is performed by virtual machine communication code  335 . In one embodiment, application of the new network configuration settings includes configuring guest operating system  330  and virtual NIC  210  such that the new network connection is the current connection. In this case, the new network connection may be tested by the guest operating system  330  or NIC  210  to confirm that the connection is operating correctly. Applying the settings may also allow guest operating system  330  and NIC  210  to connect to the network connection and retrieve additional connection information. This is discussed in more detail below.  
      Next, additional connection setting information may optionally be retrieved by guest operating system  330  from the new network at step  850 . In this optional step, guest operating system  330  may need to retrieve additional information from the new network in order to establish a connection with the network. The additional information may include a new DNS server address, updated routing information or other information. The dashed line comprising the box illustrating step  850  indicates this step is optional. The complete set of network configuration settings are then saved at step  860 . Saving the network configuration settings at step  860  is similar to saving the configuration settings at step  760  of  FIG. 7  discussed above. The settings may be stored along with a tag generated by a host operating system naming scheme, a hash operation or some other method. The stored setting may be retrieved as discussed above with respect to step  620  of  FIG. 6 .  
      The foregoing detailed description of the technology herein has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the technology to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The described embodiments were chosen in order to best explain the principles of the technology and its practical application to thereby enable others skilled in the art to best utilize the technology in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the technology be defined by the claims appended hereto.