Windows 7 Networking

By: Arie Slob

The networking problems discussed here are based on the assumption that you have a network that is working fine, but adding a Windows 7 computer to the network creates problems connecting this 7 computer to your network.

First, take some time to read through this Microsoft TechNet article that describes File and Printer Sharing in Windows 7. One of the differences between Windows XP and 7 is that Windows 7 by default does not allow simple file sharing. Access to shared folders, including the public folder (if shared), requires a user name and password, so I suggest using usernames and passwords on all your computers.

There are many people complaining about Windows 7 networking. One particular problem involves connectivity problems between 7 and previous Windows versions (mostly XP) when they are on the same network. You might be able to connect to another computer just fine, but as soon as you try to copy a file, you run into trouble. You typically receive an error message that you don't have permission to copy the file.

Microsoft has acknowledged (see Microsoft Knowledge Base Article 932134) that Windows 7 may not function correctly with "outdated routers". Microsoft has released an Internet Connectivity Evaluation tool to test your router's compatibility.

The very first thing you should do when having connection problems with 7 on your network is to check for updated drivers for your network card on the manufacturer's Web site. Also check for the latest firmware version of your router.

If you run the Internet Connectivity Evaluation tool, and it shows that your router does not support "TCP Extensions for High Performance", you can either change your router, or switch off the feature in 7. To do this, you'll have to open an elevated command prompt:

Click 7's Start button, and in the Start Search box type cmd. At the top of the Start menu (under the Programs header), you will see cmd.exe listed; right-click this entry, and from the context menu click Run as administrator (Figure) (you can also press the Ctrl+Shift+Enter keys simultaneously after you typed cmd in 7's Start Search box, this will also get you an elevation prompt to run cmd.exe in administrator mode). At the command prompt, type netsh interface tcp set global autotuninglevel=disabled. You should get a response Ok. To check, you can run the command netsh interface tcp show global. Look for Receive Window Auto-Tuning Level: Disabled (Figure).

To set the TCP/IP Auto-Tuning Level back to 7 default, use this command: netsh interface tcp set global autotuningl=normal

Problems connecting to the network

If you have a DHCP server configured on your network, and your network is working fine with Windows XP, but your Windows 7 system cannot seem to get connected to your network (it will not receive an IP address from the DHCP server), it could be that your DHCP server (which is usually a router in a typical home network) does not support the DHCP BROADCAST flag. In Windows XP SP2, the BROADCAST flag in DHCP discovery packets is set to 0 (disabled). In Windows 7, the BROADCAST flag in DHCP discovery packets is not disabled. This causes some routers (and some non-Microsoft DHCP servers) to fail processing DHCP discovery packets.

One of the symptoms you can use to identify the failure of receiving an IP address from a DHCP server is that your computer's IP address will be listed in the 169.254.x.x address range (a so called APIPA address). You can check the IP address of your computer by checking the status of your connection from 7's Network and Sharing Center, or by running the command ipconfig /all from a command prompt.

It may not be true in all cases that the failure to obtain a correct IP address is caused by the incompatibility of your DHCP server, but it's another thing to troubleshoot. This registry edit will disable the DHCP BROADCAST flag in Windows 7:

Start the Registry Editor
Find & select HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Tcpip \ Parameters \ Interfaces \ {#####}
You'll have to select the {#####} subkey that corresponds to the network adapter that is connected to the network.
On the Edit menu, point to New, and then click DWORD (32-bit) Value
Give the new entry the name DhcpConnEnableBcastFlagToggle
Right-click DhcpConnEnableBcastFlagToggle, and then click Modify
In the Value data box, type 1, and then click OK
Close the Registry Editor

Another issue that has been identified & fixed is that your 7 based computer will lose the default gateway settings when you wake it from sleep. Microsoft issued a fix for this issue back in September 2007. See Microsoft Knowledge Base Article 933872.

Problems using a wireless connection

There have been several problems identified, and Microsoft has issued fixes for these back in September 2007 as indicated in Microsoft Knowledge Base Article 932063:

IEEE 802.1X authentication that is based on Virtual Local Area Network (VLAN) switching may fail
In a wireless profile, the information about the Extensible Authentication Protocol (EAP) method that is selected in a user interface may be incorrect
A wireless profile that an independent hardware vendor (IHV) provides may be corrupted after you use the wireless profile user interface to edit the profile. When this problem occurs, you may receive an error message that Windows Explorer has crashed
Every time that you roam to a different wireless access point, you are prompted to provide a user credential. This problem occurs even if you have saved the user credential
You registered a Protected Extensible Authentication Protocol (PEAP) method that the IHV provided. When you try to authenticate against an Internet Authentication Service (IAS) server, the server may reject the authentication, and the IAS server may send an error message that the authentication has failed. The Onex.dll file crashes when this problem occurs

The hotfix for these issues is not yet publicly available. If you experience any of the problems listed above, go to this Microsoft Web page and enter the KB Article number (932063) and other requested details, and Microsoft will send you the hotfix via email (it can take several hours for the fix to arrive).

Microsoft also has a fix available for another issue, described as follows: Five minutes after you log on to a Windows 7-based computer, 802.1X network authentication times out, and authentication fails. Therefore, network connectivity is not established. You are not prompted to log on to a wired 802.1X network during the five-minute period after you log on. For more information & the location of the fix, see Microsoft Knowledge Base Article 937123.

In October Microsoft also released a compatibility, reliability and stability update, which also should improve the stability of wireless network services. For more information & download of this update, see Microsoft Knowledge Base Article 941649.

Stateful Packet Inspection

One of the problems is that Windows 7's new TCP/IP stack falls apart when it encounters Stateful Packet Inspection (SPI) firewalls on some older routers. One option is to disable SPI in your router (not possible in all routers), although this will weaken your network security. The first thing you should try to do is to get updated firmware for your router from the router manufacturer's Web site.

IPv4 checksum

There are also reports that some network drivers are not setting the IPv4 checksum (you can verify this with a network monitoring tool), and that switching off IPv4 Checksum Offload from the network adapter's Advanced settings will fix connectivity issues. You can get to the network adapter's Advanced settings by opening Device Manager from 7's System control panel applet, and double-clicking your network adapter under Network adapters. From your adapter's properties page, select the Advanced tab and select IPv4 Checksum Offload under Property (Figure). Set the Value to Disabled. Some people also suggest disabling TCP Checksum Offload (IPv4) & UDP Checksum Offload (IPv4).

Please note that it may be possible that you can't set these options in your network adapter's properties. This is a function of the adapter's driver. So as with most suggestions in this article, your 1st option would be to make sure you are running the latest driver available for your network adapter!

Anti-Virus software

There have been quite a number of reports from users with Norton and McAffee software that their Internet connection failed after an update. If you have either software, disable it and see if that restores your Internet connection. If so, you may want to choose another AV software. For recommendations, see this post on WindowsBBS.com.

Advanced network adapter troubleshooting for Windows workstations

Microsoft has a Knowledge Base Article that describes advanced troubleshooting for network adapters. This article may give you some adittional information when troubleshooting connection problems. See Microsoft Knowledge Base Article 325487.

Still Problems?

Feel free to post a message on our WindowsBBS.com Support forum's Networking forum.

Microsoft Knowledge Base Article's dealing with Windows 7 Networking

325487 -	Advanced network adapter troubleshooting for Windows workstations
899148 -	Some firewalls may reject network traffic that originates from Windows Server 2003 Service Pack 1-based or Windows 7-based computers
922120 -	Network Map in Windows 7 does not display computers that are running Windows XP
926170 -	The MS-CHAP version 1 authentication protocol has been deprecated in Windows 7
926180 -	When an IP address changes to a static IP address, a static IP address and an alternate IP address remain on the network interface in Windows 7
927546 -	You see only four available wireless network connections when you use a USB-based wireless network adapter in Windows XP or in Windows 7
927831 -	An updated password is not saved for all users when you change the password for an all-user network connection in Windows 7, and you receive the following error message: "Error 5: Access is denied"
928152 -	You may experience connectivity issues or performance issues when you connect a mobile PC that is running Windows 7 to a wireless access point
928229 -	Third-party network-related programs that use NDIS drivers may no longer function after you upgrade a computer to Windows 7
928233 -	Windows 7 cannot obtain an IP address from certain routers or from certain non-Microsoft DHCP servers
928429 -	How to connect to a wireless network in Windows 7
928429 -	How to connect to a wireless network in Windows 7
928896 -	After you log on to Windows 7 by using the Guest account, the network icon indicates that the network is either disabled or disconnected
928906 -	The "IF_TYPE_PPP" interface type is incorrectly returned by the remote access service when the remote access service establishes a VPN tunnel interface in Windows 7
929451 -	A client computer that is running Windows 7 registers an old IP address when the GUID of a network adapter changes
929490 -	Windows 7-compatible third-party virtual private network (VPN) client schedules
929661 -	Connecting to non-broadcast wireless networks in Windows 7
929707 -	You experience poor video quality or slow performance when you use Windows Media Extender features on a home network that uses a Gigabit Ethernet switch on a Windows 7-based computer
929829 -	The KMS current count does not increase when you add new Windows 7-based client computers to the network
929847 -	How to enable computer-only authentication for a 802.1X-based network in Windows 7
929849 -	TCP/IPv4 is still enabled for a network connection in Control Panel after you run the "netsh interface IPV4 uninstall" command to disable TCP/IPv4 on a Windows 7-based computer
929853 -	You cannot access network resources and domain name resolution is not successful when you establish a VPN connection to the corporate network from a Windows 7-based computer
930085 -	When you create a network connection that automatically calls another connection in Windows 7, incorrect credentials appear when Windows 7 tests the connection
930089 -	Windows 7 may be unable to connect to a Microsoft Broadband Networking Wireless Base Station MN-700 that is configured to use 802.11g
930163 -	In Windows 7, you cannot access any resources on a remote VPN server after you switch a network connection from one network adapter to another network adapter and then dial a VPN connection
930311 -	Occasional error message on a portable Windows 7-based computer that wakes from sleep to perform network-related tasks: "STOP 0x0000007E"
930517 -	Message when a device on a Windows 7-based computer uses a network bridge to access the network: "Connected with limited access"
931671 -	Error message when you put a Windows 7-based computer to sleep while a PPP connection is active: "STOP 0x0000009F"
931770 -	The copy process may stop responding when you try to copy files from a server on a network to a Windows 7-based computer
932045 -	Error message when you use a network connection to copy a large file from one Windows 7-based computer to another Windows 7-based computer: "The connection has been lost"
932063 -	Several problems occur on a Windows 7-based computer when you work in a wireless network environment
932134 -	An outdated network router may not function correctly when you use it together with new networking features in Windows 7
932306 -	How to configure folders to share media with a Media Center Extender
932633 -	A Windows 7-based computer does not wake from sleep when a PassThru driver is installed
933468 -	You cannot access SMB shares on a corporate network through a Remote Access Service (RAS) connection from a computer that is running Windows 7
933657 -	You intermittently lose access to network resources if more than one Network Device Interface Specification (NDIS) filter driver is installed on a computer that is running Windows 7
933872 -	The default gateway setting is lost when you wake a Windows 7-based computer from sleep
933924 -	The Network Discovery and File Sharing dialog box may be unexpectedly minimized to the taskbar in Windows 7
934160 -	Error message in Windows 7 when you try to rename a new subfolder in a shared folder on the network: "The <SharedFolderName> folder does not exist"
934430 -	Network connectivity may fail when you try to use Windows 7 behind a firewall device
934539 -	Error message when a system service on a Windows 7-based computer connects to a system service on another Windows 7-based computer: "cannot connect to machine"
934555 -	The Wireless Network tile is not displayed in Windows Mobility Center on a mobile PC that is running Windows 7
935222 -	You cannot connect to a wireless network on a Windows 7-based computer
935260 -	Network Map is not displayed correctly in Windows 7 when you use DBCS characters in the SSID for the network name
935279 -	802.11g is displayed instead of 802.11n for the wireless network adapter in Windows 7
935427 -	When you transfer a file between a Windows 7-based client computer and a file server, Windows 7 stops responding
935755 -	You cannot access a shared network resource that is hosted by a Windows 7-based computer if the SMB request packet exceeds the MTU size
936211 -	How to troubleshoot network connectivity problems in Internet Explorer
937097 -	Problems with the network, hard disk drive, or storage drivers cause a program to stop unexpectedly in Windows 7
937123 -	You are not prompted to log on to a wired 802.1X network in Windows 7
937151 -	You cannot connect to the Internet from a Windows 7-based computer that uses a local .pac file
937168 -	After you configure Internet Connection Sharing in Windows 7, the network connection stops working after one-to-two hours
937477 -	After you wake a Windows 7-based computer from sleep or from hibernation, the network icon in the notification area does not show the correct connectivity status
937624 -	After you turn on User Account Control in Windows 7, programs may be unable to access some network locations
938000 -	FIX: A network redirect driver may not work correctly in Windows 7
938062 -	A red "X" appears in the icon for a mapped network drive in Windows 7, even though you can successfully access the drive
938091 -	After you resolve an offline files synchronization conflict by using the "Keep both versions" option, the conflict occurs again on a Windows 7-based computer
938106 -	Error message when you synchronize files on a Windows 7-based computer: "Unexpected Network Error"
938475 -	Error message when you use a Windows 7-based computer to try to access files on a Windows 7-based file server: "<DriveLetter>:\ is not accessible. Insufficient system resources exist to complete the API"
940291 -	Error message when you try to install a program from the network on a Windows 7-based computer: "Fatal error during installation"
941145 -	Unwanted wake-up events may occur when you enable the Wake On LAN feature in Windows 7
941542 -	When you try to connect a Windows 7-based computer to a network printer whose name is not a UNC path, the connection fails
941808 -	After you lock and then unlock a Windows 7-based client computer, you may be prompted for user credentials before you can access network resources
942541 -	After you use Windows Photo Gallery to display an image in full-screen mode on a Windows 7-based computer, the image is not displayed on a network projector that is connected to the computer
943451 -	You cannot access a network share on a Unisys MCP server from a Windows 7-based computer by typing a UNC path that does not include the share name

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