Power BI

Content by Charles Sterling

Testers SIG Recap (-and why DHCP didn’t work in Virtual PC)

Yesterday at the Testers SIG we had packed agenda and a packed house! Starting with an introduction to testing in Agile development by Amir at Net Objectives, did a walk through of recording a manual test, taking the recording and turning it into a coded test and finally adding additional functionality by recording control IDs and values to make decision points in our tests….

The feedback was great and the turn out was amazing (we almost ran out of donuts!!!). 

Unfortunately the day didn’t go without some hiccups.  I wandered into the lab at ~11:00am to an unhappy lab tech and a nonplussed Naysawn Naderi.  Friday Naysawn had everything working perfectly in a virtual environment.  9:00am Monday they copy the images to the 22 machines in the lab -and everything STOPS working.  Unfortunately the real reason was masked by some networking issues in the building and the fact we were updating the images.  After the session had started it was either Mark or Euan that noticed all the images had the same IP Address! -despite DHCP running <sigh>. I set two of the computers to use static addresses but it was too little too late for the portions of the lab connecting to TFS.  

Turns out the dynamic IP address issued by the DHCP Server is based on the computers Network MAC address – and in this case all 22 computers were exactly the same.  I did a quick look at the settings in Virtual PC to see if i could find a place to change this – but we don’t have any UI for it<sigh>.  If i had just hit the F1 key i would have found the answer(see below).  I am guessing the only reason we hadn’t hit this before is we just shipped the VHD over and created new the new VMC on the 22 hosts.  


Cause:  If you create an image of a host operating system that includes Virtual PC and virtual machines configuration files (.vmc files) and copy that image to another computer, each virtual machine configuration file included in the image contains a MAC address. The MAC address will not be reset automatically when you place the image on a new physical computer. As a result, the virtual machines that are copied onto the new computer will have the same MAC addresses as the virtual machines on the computer that was used to create the image.

Solution:  Edit the .vmc file to remove the MAC address. Find the following line:

<ethernet_card_address type=”bytes”>0003FFxxxxxx</ethernet_card_address>

Remove the number so the line appears as follows:

<ethernet_card_address type=”bytes”></ethernet_card_address>

After you remove the number, Virtual PC will create a new MAC address the next time you start the virtual machine.