One PC on my Wireless LAN cannot connect to internet

Microsoft Windows Vista
Netgear router
Wireless Internet
Wireless networking
I have a wireless LAN using ADSL. I have connected five PCs with no problem but there is one (Vista) laptop that connects fine to the router but the 'network map' in the 'network and sharing center' shows a red cross between the router and the internet. Windows troubleshooter doesn't fix the problem. Any help in where (and how) to look for a solution would be much appreciated. Steve

Software/Hardware used:
Netgear Router, Acer Laptop, Vista

Answer Wiki

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I did extensive testing on Vista connecting to SOHO type routers when Vista first came out. Vista changed how the DHCP client works and caused many headaches for people. My guess on the issue is a failure to obtain an IP address from the DHCP service of the router.

Check on your Vista system to see if you have an IP address from the router and not an APIPA address. If the IP address is 169.254.x.x then it is an APIPA address. This indicates that your system failed to get a DHCP assigned address from your router.

The issue with Vista and many SOHO (and other) routers is that Vista sets the DHCP Broadcast Flag (a DCHP option) in its DHCP requests. The routers do not understand the DHCP Broadcast Flag and drop the request. Microsoft “fixed” this is Windows 7 by sending the first request with the DHCP Broadcast Flag and the second request without then repeating this patern.

Turning off the DHCP Broadcast Flag does not appear to negatively affect DHCP requests to systems that understand the flag and can fix issues on systems that do not understand the DHCP Broadcast Flag. I found that additional changes were sometimes needed.

Microsoft has an article that changes Vista’s DHCP request to match Windows 7. Most times this will resolve the DHCP failure to obtain an IP address. The article also has a FIXIT to automate the resolution.

According to the KB this works on Vista from the release version forward.

Disable the DHCP Broadcast Flag (kb928233)

1. Go to Start and type in regedit and press Enter.
2. Locate and then click the following registry subkey

3. HKLM SYSTEM CurrentControlSet Services Tcpip Parameters Interfaces {GUID}

(I tried the CODE tags but the registry path failed to show so here it is without the backslashes)

4. In this registry path, click the (GUID) subkey to be updated.
5. If the key <b>DhcpConnEnableBcastFlagToggle</b> does not exist, use the Edit menu, point to New, and then click DWORD (32-bit) Value. In the New Value #1 box, type DhcpConnEnableBcastFlagToggle, and then press ENTER. If the key exists, skip this step.
6. Right-click DhcpConnEnableBcastFlagToggle, and then click Modify.
7. In the Value data box, type 1, and then click OK.
8. Close Registry Editor.

NOTE: If you do not know which interfaces you have this issue on you may want to do this for each and every GUID subkey.

If this does not resolve a failure to obtain a DHCP address I have used additional potential solution of Disabling the DHCP broadcast flag and turning off IPv6 on the interface.

Discuss This Question: 4  Replies

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  • Subhendu Sen
    May be SixBall's inputs help the Q asker !
    141,290 pointsBadges:
  • Sixball
    Lets hope, eh? :)
    8,705 pointsBadges:
  • jinteik
    how about the services, dhcp client, started automatic?
    18,995 pointsBadges:
  • Hahahaa
    i think you should insert the mac address in the router of the vista laptop.
    205 pointsBadges:

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