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12. ianuarie 2009 16:53
by skorpionking
0 Comentarii

.NET: Virtual PC 2007 Shared Networking (NAT) Internet not working in Windows XP Guest OS

12. ianuarie 2009 16:53 by skorpionking | 0 Comentarii

Even if I've used many times Virtual PC in Vista or XP or Windows Server 2003 or 2008 (both as guest and host OS), today I ran in apparently known problem: my guest XP wasn't able to connect to Internet even if I've chosen shared NAT for the Internet connection.

Here is explained what is going on: "NAT (Network Address Translation) is an easy shared networking technique that masquerading or transceiving network traffic through a router that involves re-writing the source and/or destination IP Addresses and the TCP/UDP port numbers of IP packets as they pass through. In the case of Virtual PC, it uses a virtual NAT router which built on host computer’s default active network connection to allow guest operating system to access Internet via the host’s Internet connection.

Shared Networking or NAT allows computers or hosts on a private network to access the Internet using a single IP address, without exposing the PCs (or virtual machines) to the external network, significantly reduce security risk. NAT is also useful to allow virtually unlimited number of IP addresses to connect to Internet, thus administrator is not limited by the amount of IANA assigned-IP address allocated space. Beside, Shared Network (NAT) allows user to easily plug and play or move the virtual machine or physical machine to different network configurations such as different Wi-Fi wireless access point, home or office network.

Most computers, including Virtual PC 2007 virtual machines can easily access Internet using Shared Networking, as easy as right after operating system is installed, which enable DHCP by default. The problem is that Shared Networking configures the guest operating system to use the same DNS servers as are used by the physical computer. However, when actual DNS query resolving packets are been returned, it’s actually returned from the IP address of “″, which is the virtual gateway used by Shared Networking (NAT). Windows Server 2003, Windows Server 2008 and Windows Vista or XP will reject any DNS resolution packets that are returned from a different source from than the DNS Server (both has different IP address) that it had requested the information from. As thus, all name resolution of domain name and URL fails, indirectly leads to the guest operating system appears to be cannot connect to Internet."

To fix the Shared Network (NAT) Internet no connection or not working issue, the resolution is to manually assign the IP address for the DNS Server for the guest operating system to, the virtual gateway IP address used by Virtual PC. To make the change (in guest operating system), open Network Connections folder (in Windows Vista, access via Network and Sharing Center), and right click Local Area Connection network icon to select its Properties. Then double click on Internet Protocl (TCP/IP) under General tab or Internet Protocol Version 4 (TCP/IPv4) under Networking (for Windows Vista) tab.

Click to select the radio button of Use the following DNS server addresses, and then type in into the IP address box for Preferred DNS Server. Click OK twice to exit, and voila, the Shared Network (NAT) now works as it should with Internet access.

If you still have problems with the connectivity, please see also the article about invalid DNS server assigned by Virtual PC network adapter.