VMWare Fusion XP VM Losing DNS !

October 25, 2008

I’ve been running OSX Vmware Fusion 1.x and XP SP2 & SP3 for over a year and it’s been ROCK SOLID ! I run a web-connected OSX host, and a XP VM VPN’d into a corporate network all day, every day and I have not had a single problem. Until this week…when my calm seas were interrupted…

Out of the blue I notice witin the XP SP3 VM was failing to resolve DNS queries. OK. Why? I basically ran a number of diagonstics, checked driver versions and everything checked out in terms of VM integrity.No idea. The worst kind of problem…

I checked out the net and located numerous threads deliberating over the XP “Unable to flush DNS cache” type of errors, with long and elaborate threads falling into the detail of comparing router firmware versions and other such infinate variables. Eject..Eject…

It was only when I ran the VMWare packet sniffer on the OSX host I could see that the XP VM was requesting DNS, and the resoponses from the OSX host were being dispatched. From my understanding of low level IP it appeared that all was performing as expected. However I then started thinking about reasons why UDP packets were being neglected by the XP VM’s IP stack….BINGO !

I then checked out the Windows XP Event Viewer under the Security event list, and there I see all my DNS responses (from the OS X host) arriving back at my XP VM as UDP packets, all being summarily discarded by my failed/corrupted firewall. Couple of minutes later, having run the ‘support’ utility from the firewall supplier, the flood-gates openend and UDP/DNS was back in business.

Symptoms I encountered in XP:

  1. DNS resolution (i.e. ping http://www.xyz.com) within XP VM failing but direct direct addressing worked ok (i.e. ping
  2. nslookup in the console returned ‘no response from server’ errors in response to queries.
  3. Right-clicking on the network connection icon in XP, and executing Repair proceeded through all steps apart from the final DNS cache at which point Unable to repair connection was returned.
  4. ipconfig /registerdns failed with a non-specific error

In hindsight the symptoms all point to UDP return-path and firewall but verifying the request path with the OSX VMWare vmnet-sniffer utility (located in /Library/Application Support/VMWare Fusion folder) made this a whole lot simpler.


VMWare Fusion and Intermittent XP VM Networking

August 19, 2008

This is a strange one that’s been perplexing me. VMWare Fusion 1.1.3, running WinXP SP2 solid as a rock for nearly 9 months. I use a NAT networking configuration on my XP VM, relying on my Macbook Pro host to establish a wired/wireless connection to the web, which is then shared by the VM. As I say – s-o-l-i-d as a rock!

Recently though I noticed an increasing trend of the XP VM networking manager informing me that the XP networking connection was partially configured after a failed initialisation, and therefore offered limited functionality – which meant NO connection in reality.

I trawled the web/forums for support but predictably stumbled across the same mix of affliction and useless assistance like “..er…reinstall everyting and that should do it” from “yours faithfully the new guy on the support desk just trying to make a living by reading page 1 of the firefighting guide” or the equally ridiculous and unhelpful help from the geek who believes packing as many three-letter-acronyms into every uttered statement as possible.

Ultimately I drew a blank on the support front which was very disappointing. I did however happen across an innocuous statement relating to DHCP and some kind of limitation when acquiring IP addresses over a wireless link. As such I began musing about whether ‘things’ or ‘services’ in my XP startup may be interfering with my XP IP stack obtaining full configuration. However, logic was screaming at me that all services using IP rely on the underlying IP stack to obtain it’s address which is then shared by port number specific socket users…but still I went with the flow…

What follows cannot be explained (by me anyhow) in scientific terms. I opened XP servivce manager, and stopped a range of services like Postgres, Mysql, Sqlserver, and some others I wasn’t clear on the use of. That was the only change I made.

To my surprise, my rock-solid XP VM stability returned with guaranteed networking every time ! I offer this post not as a technically enriching article, but as a last stop for those as desperate as I was when afflicted by this intermittent yet highly painful symptom !

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VMWare Fusion, OS-X and Large Files

August 19, 2008

I’ve been using VMWare Fusion running an XP Virtual Machine on my Macbook Pro for 9 months now, and it’s been rock solid. There are reasons (corporate) why I need to have a specific XP build for accessing certain business support systems hence why I’ve not made the OS-X conversion all the way. I’ve been trying to replicate my XP VM onto another external drive. The image is 40GB. Computers says NOOOOOO !

I was receiving an unhelpful Error 0 from the drag-n-drop copier in the OS-X Finder, and when I dropped to a terminal window it was copying around 4 gigabytes before complaining the file was too large….yeah…it made me wait before telling me that ! So how do I move a large file?

I checked out VMWare forums who recommended using vdisk-manager (and it’s many complicated parameters) to chunk the image into 2GB files. There was also chatter of using the VMWare Fusion advanced applications settings to set the flag to ‘break image into 2GB files’ but it turns out that option is only relevant to newly created image files.

To cut a long and painful story short, after trying many weird and wonderful options, I used the following command:

# split -b 2048m /Users/Name/Documents/Virtuals/source.vmdk /Volumes/USB Drive Name/dest

This successfully broke up my 40GB source file into a file-set, using a aa..nn suffix, in my destination like:

# ls /Volumes/USD Drive Name =>

destaa, destab, destac, destad .. destat

I was then able to move my VM onto another host and reconsitute the backup with a neat bit of ruby scripting (as an alternative to a long-winded command-line). Something along the lines of:

cmdline=’cat ‘

for suff in ‘aa’..’at’ do

cmdline << “dest#{suff} “


cmdline << “> source.vmdk”


This a long-running yet simple solution to something I’d been struggling with for a couple of hours, and there was no need for any external tools or complexities.

The copied VM works perfectly too…but I accept no resposibility for anyone who fluffs this approach !

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