Strange DNS problem

brochs · Post by **brochs** » 9. Sep 2009, 10:20

HI,

I am having a very strange problem on Windows 7 x 64 host. When running guests in NIC bridge mode I get a IP from DHCP on guests, I can ping all IP addresses both private and on internet, but pinging e.g. www.pcworld.com I get no response. Clearly it’s something with the DNS which is the same as my host use, and I can ping it from guest. Setting guest OS to NAT everything works just fine.
The problem exist in both windows and Linux guests (X86). Someone have any ideas? I have to mention that I have tried VMware Desktop and get the same problem there.

Post by **vbox4me2** » 9. Sep 2009, 12:57

Check the exact IP values between Host and Guest, probably the gateway is missing.

brochs · Post by **brochs** » 9. Sep 2009, 15:16

vbox4me2 wrote:Check the exact IP values between Host and Guest, probably the gateway is missing.

No, the Gateway is not missing, without the right gateway I woul not be able to ping official IP's on the internet.

Post by **vbox4me2** » 9. Sep 2009, 20:21

Did you check the other values? it can very well be your router is misconfigured, see the quickclick FAQ.

brochs · Post by **brochs** » 9. Sep 2009, 21:39

vbox4me2 wrote:Did you check the other values? it can very well be your router is misconfigured, see the quickclick FAQ.

Everything is checked, this is not a router problem, It has to be someting that's blocking DNS requests on the host's NIC when coming from the guest, I just cant figure out what. Could it be that the VB drivers are having problems with Windows 7? I am now using Windows 7 RTM Profesional.

Post by **Perryg** » 9. Sep 2009, 22:01

Put a known good DNS in the guest settings instead of using the routers DNS. It sounds like the first DNS entry is down or flakey and VB will only try to use the first one.

Post by **Sasquatch** » 9. Sep 2009, 22:46

If I understand the problem correctly, you can ping www.google.com without issues from both the Host and Guest, but you can't ping www.pcworld.com? So it's only that one specific site? If so, then it's normal. I can't ping it on my end either, but I do get the DNS name resolved. Some sites don't allow ping, because it can be used for a (D)DoS attack.

brochs · Post by **brochs** » 10. Sep 2009, 20:36

Sasquatch wrote:If I understand the problem correctly, you can ping http://www.google.com without issues from both the Host and Guest, but you can't ping http://www.pcworld.com? So it's only that one specific site? If so, then it's normal. I can't ping it on my end either, but I do get the DNS name resolved. Some sites don't allow ping, because it can be used for a (D)DoS attack.

No, that is not right. I can ping 74.125.79.147 (witch is Google), but I can't ping www.google.no or any other site by name only by IP.

And to the previous post: since my router only give out one DNS server from DHCP, 192.168.97.1 (same as gw) and the router have several DNS servers in it's WAN setup I am also sure that it's not my DNS that's not responding.

Post by **Perryg** » 10. Sep 2009, 20:38

Did you try to put in a known good DNS on the guest?

Post by **vbox4me2** » 10. Sep 2009, 22:11

Can you ping the DNS/router? do a tracert to the DNS and the DNS of your ISP.

brochs · Post by **brochs** » 11. Sep 2009, 08:59

vbox4me2 wrote:Can you ping the DNS/router? do a tracert to the DNS and the DNS of your ISP.

I have tried everything to make sure the DNS is good. Also as I write in my first post, it's the same DNS and gw as I have on my host system, and no problems what so ever here. That's why this is so strange. My guess would be that Windows 7 in some way block the DNS traffic as the Virtual bridge NIC of the guest have to pass the NIC of the host.

Post by **vbox4me2** » 11. Sep 2009, 09:52

I've seen such an issue which was related to firewall rules on the Host.

brochs · Post by **brochs** » 11. Sep 2009, 10:40

vbox4me2 wrote:I've seen such an issue which was related to firewall rules on the Host.

That was the first thing I was thinking to, but turning FireWall off did'nt fix the problem

Post by **Sasquatch** » 11. Sep 2009, 11:02

Turning off a firewall doesn't always work. Sometimes you need to set it to accept all, or even remove it completely before it starts to work properly again. After the test, you can reinstall it, the settings should have stayed behind.

brochs · Post by **brochs** » 11. Sep 2009, 22:50

Sasquatch wrote:Turning off a firewall doesn't always work. Sometimes you need to set it to accept all, or even remove it completely before it starts to work properly again. After the test, you can reinstall it, the settings should have stayed behind.

As I don't have any third party FW installed, only the one that comes with Windows 7, uninstaling is not an option. But I am sure that turning it off is all that's needed if that was the problem.

I am sure this is not a network problem, it has to be some kind of problem with the fact this beeing Windows 7 (maybe also 64bit), I have not tried Virtualbox with Vista so I can't say if the same problem exists there.

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