# Solved: Windows 7 laptop losing DNS



## oldsch00l (Apr 30, 2012)

Hi,

I have an issue whereby my Windows 7 (Professional 32bit) Toshiba Satellite Pro laptop is losing its ability to resolve DNS when connected wirelessly to my BT Homehub (combined ADSL modem/wireless router). I have had the same laptop and Homehub for over two years and this has only started happening in the last couple of weeks. I cannot pinpoint any h/w or s/w changes that have been made and could account for this behaviour.

When the issue occurs (typically after 15-30 minutes of normal internet browsing) I can no longer view web sites or ping, for example, www.google.com. I can, however, ping the Homehub and localhost by ip address. Some other non DNS-reliant services such as Skype, email etc may continue to work also.

The only way I have found to reliably regain working DNS is to restart the laptop. Other attempts, such as disabling/enabling the NIC releasing/renewing IP and flushing DNS cache have no effect.

Some initial troubleshooting steps I have exhausted are:

- disabling all AV/firewall software - the problem remains.
- Several restarts and finally a full factory reset of the Homehub - no joy.
- uninstalled/reinstalled the wireless NIC (Realtek RTL8191SE) and made sure I have the latest drivers.
- Removed all other devices from the network to ensure there is no IP clash.
- Laptop rolled back to a known good restore point.

I have an XP laptop on the same wireless network that does not suffer from this issue, so I know the actual connection is not at fault. I use the Windows 7 laptop on another wirelsess network (at work) and it is rock solid for 8 hours +. So, it looks to be something specific to the combination of the BT Homehub and the Win 7 laptop.

Worth noting, before anyone suggests doing so, the wired NIC on the Windows 7 laptop does not work so I am unable to connect directly to the Homehub with an Ethernet cable.

By default the laptop is set to obtain its DNS servers and ip address from the Homehub via DHCP  the resultant ipconfig looks like this:

C:\Users\rlennox>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : GLOWZ9297647K
Primary Dns Suffix . . . . . . . : internal.rmplc.net
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : internal.rmplc.net

Wireless LAN adapter Wireless Network Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8191SE Wireless LAN 802.11n PCI-E NIC
Physical Address. . . . . . . . . : 70-1A-04-20-6F-D3
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::a9d5:ddf4:1c36:44b4%22(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.72(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.254
DHCPv6 IAID . . . . . . . . . . . : 544217604
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-12-B6-24-8C-00-26-22-F7-97-76

DNS Servers . . . . . . . . . . . : 192.168.1.254
NetBIOS over Tcpip. . . . . . . . : Enabled

Wireless LAN adapter Wireless Network Connection 2:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Virtual WiFi Miniport Adapter
Physical Address. . . . . . . . . : 70-1A-04-20-6F-D3
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Local Area Connection:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe FE Family Controller
Physical Address. . . . . . . . . : 00-26-22-F7-97-76
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

When I lose DNS the ipconfig data does not appear to change in any way.

My next step was to set a static IP for the laptop and specify the DNS server addresses. The resulting ipconfig is as below. As before, this will work for somewhere between 10 min and half an hour before bombing out in the same way.

C:\Users\rlennox>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : GLOWZ9297647K
Primary Dns Suffix . . . . . . . : internal.rmplc.net
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : internal.rmplc.net

Wireless LAN adapter Wireless Network Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8191SE Wireless LAN 802.11n PCI-E NIC
Physical Address. . . . . . . . . : 70-1A-04-20-6F-D3
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::a9d5:ddf4:1c36:44b4%22(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.252(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.254
DHCPv6 IAID . . . . . . . . . . . : 544217604
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-12-B6-24-8C-00-26-22-F7-97-76

DNS Servers . . . . . . . . . . . : 62.6.40.178
62.6.40.162
NetBIOS over Tcpip. . . . . . . . : Enabled

Wireless LAN adapter Wireless Network Connection 2:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Virtual WiFi Miniport Adapter
Physical Address. . . . . . . . . : 70-1A-04-20-6F-D3
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Local Area Connection:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe FE Family Controller
Physical Address. . . . . . . . . : 00-26-22-F7-97-76
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

Any further pointers would be very much appreciated as I am now at a bit of a dead end...

Thanks in advance,

Ross


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## TerryNet (Mar 23, 2005)

Just so you know, you can still do 'obtain IP auto' but specify the desired DNS server(s).

What security application(s) do, or did you ever, have on the system?

*TCP/IP stack repair options for use with Vista or 7. *

Start - All Programs - Accessories and right click on Command Prompt, select "Run as Administrator" to open a command prompt.

Reset WINSOCK entries to installation defaults: *netsh winsock reset catalog*

Reset IPv4 TCP/IP stack to installation defaults. *netsh int ipv4 reset reset.log*

Reset IPv6 TCP/IP stack to installation defaults. *netsh int ipv6 reset reset.log*

Reboot the machine.


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## TerryNet (Mar 23, 2005)

Forgot to ask ... That wireless driver is the latest from Toshiba's web site, right?


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## Couriant (Mar 26, 2002)

You didn't specify that you are able to ping by IP address when this happens (one of google's is 74.125.227.130)

Also if you set your DNS to 8.8.8.8 and 8.8.4.4, do you experience the same thing?


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## oldsch00l (Apr 30, 2012)

Thank you both for your responses - problem resolved over at the BT forum. Looks to have been a router firmware issue...

Thanks again,

Ross


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