# Windows – DNS resolution on Windows 7

dnswindows 7

I have Windows 7 and MacOS on Macbook Pro with cable internet connection in hotel. When I am using MacOS, internet connection is just fine. When I am using Windows 7, there is no internet connection. After digging a bit found that DNS resolution is causing the problem, simply names are not resolved. I installed Wireshark and strangely I found in the capture the response to DNS resolution request with resolved IP, but somehow they are not reaching Windows 7 core. Not sure if it's related or not, but after each response I see single STP packet.

The network is using DHCP to setup interface and in both OS's interfaces are setting up identically. I can ping DNS servers, default GW from Windows 7

Update:

nslookup

C:\>nslookup
DNS request timed out.
timeout was 2 seconds.
Default Server:  UnKnown

> Yahoo.com
Server:  UnKnown

DNS request timed out.
timeout was 2 seconds.
DNS request timed out.
timeout was 2 seconds.
DNS request timed out.
timeout was 2 seconds.
DNS request timed out.
timeout was 2 seconds.
*** Request to UnKnown timed-ou


ipconfig

Windows IP Configuration

Host Name . . . . . . . . . . . . : Mac-Windows 7
Primary DNS Suffix  . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Connection-specific DNS Suffix  . :
Description . . . . . . . . . . . : Broadcom NetXtreme GBabit Ethernet
Physical Address. . . . . . . . . : C4-2C-03-3B-30-8E
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 172.31.17.14(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Thursday, December 16, 2010 6:57:58 AM
Lease Expires . . . . . . . . . . : Friday, December 17, 2010 7:01:16 AM
Default Gateway . . . . . . . . . : 172.31.17.254
DHCP Server . . . . . . . . . . . : 172.31.17.254
DNS Servers . . . . . . . . . . . : 80.58.61.250
80.58.61.254
NetBIOS over Tcpip. . . . . . . . : Enabled

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix  . :
Description . . . . . . . . . . . : Microsoft ISATAP Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix  . :
Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes


trace route (result is same for macos as well)

C:\>tracert 8.8.8.8

Tracing route to 8.8.8.8 over a maximum of 30 hops

1    <1 Microsoft    <1 Microsoft    <1 Microsoft  172.31.17.254
2     *        *        *     Request timed out.
3     *        *        *     Request timed out.
4     *        *        *     Request timed out.
5     *        *        *     Request timed out.
6     *        *        *     Request timed out.
7     *        *        *     Request timed out.
8     *        *        *     Request timed out.
9     *        *        *     Request timed out.
10     *        *        *     Request timed out.
11     *        *        *     Request timed out.
12   111 Microsoft   109 Microsoft   109 Microsoft  8.8.8.8

Trace complete.


netstat

C:\>netstat

Active Connections

TCP    127.0.0.1:5357         Mac-Windows 7:49165     TIME_WAIT
TCP    127.0.0.1:5939         Mac-Windows 7:49164     ESTABLISHED
TCP    127.0.0.1:49157        Mac-Windows 7:49158     ESTABLISHED
TCP    127.0.0.1:49158        Mac-Windows 7:49157     ESTABLISHED
TCP    127.0.0.1:49160        Mac-Windows 7:49161     ESTABLISHED
TCP    127.0.0.1:49161        Mac-Windows 7:49160     ESTABLISHED
TCP    127.0.0.1:49162        Mac-Windows 7:49163     ESTABLISHED
TCP    127.0.0.1:49163        Mac-Windows 7:49162     ESTABLISHED
TCP    127.0.0.1:49164        Mac-Windows 7:5939      ESTABLISHED


• This was the reason for DNS not working with DHCP on Windows 7 in my case:

After 2 days of struggling, I suddenly noticed that when I rebooted the router (after modifiyng some basic parameter) its date was probably reset to its BIRTHDATE (2005), so the lease it was giving was in the PAST and probably Windows 7 relies on the date given by the DHCP instead of its own...

The result is that the lease is already over.

Then 2 odd things happen, you can check them with ipconfig /allcompartments /all on Windows 7, for some reason:

• Windows 7 doesn't understand the lease time: it declares more than 136 years instead of 120 minutes!
• If the lease is ALREADY OVER: Windows 7 ignores the DNS given!

To summarize the SOLUTION in my case was:

1. Setup the correct time on the DHCP server.
2. Run ipconfig /release
3. Run ipconfig /renew

DHCP with DNS shoud be UP and WORKING!

So ALWAYS check the DHCP server date...