Working with IE6 on Windows Vista - Don't Forget the Firewall

IE6 still represents about 29% (though that number is falling) of the browsers on the web.  While I would love it if every would upgrade, that's just not going to happen.  Heck, I've got a client that's still running Win2k on his business machine.  "Why would I upgrade?" he says.  "It does everything I need."  You can't argue with that.

Sure, I evangelize about the fun you can have with Firefox plugins but, let's be honest, some people don't want to install more things on their computer.  In fact, there are still people using IE5 (released in March, 1999) -- more than using Opera until just recently.  So, it's still important for anyone developing for the web to support IE6, though you can't run IE6 in side-by-side with IE7 and can't run it at all on Vista.  Now what?

There are plenty of posts about the Virtual PC solution so I won't rehash what other's have done.  Fiona has put together a concise list of instructions on her blog.  However, I would recommend a few changes from her instructions, which can be done afterwards

• From the Network settings dialog, select your network adaptor, not "Shared networking (NAT)."
• Make sure there is local access through the Windows Firewall:
  • Click the Windows (Start) button and type "firewall."  Select "Windows Firewall" (not "Windows Firewall with Advanced Security" if it appears).
  • If your firewall is off, then you're done.  Though, for security reasons, you may wish to turn on the Windows Firewall if you do not already have a firewall in place.
  • Click "change settings" and then "Continue" on the User Access Control dialog.
  • Click the "Exceptions" tab and press the "Add port..." button.
  • Name the new execption something useful, like "VPC access to localhost".  Enter "80" for "Port number" and make sure "TCP" is checked for "Protocol"
  • Click the "Change Scope" button and select "My network (subnet) only".
  • OK your way out of all those dialogs.

A subnet mask filters out IP address that are not within a given range.  You can find your subnet mask by typing "ipconfig" at a command prompt.  For example, on my development machine I get:

  IPv4 Address. . . . . . . . . . . : 192.168.16.3
  Subnet Mask . . . . . . . . . . . : 255.255.255.0
  Default Gateway . . . . . . . . . : 192.168.16.1

The subnet mask is a bit-mask.  255 means that every bit in that 8-bit chunk must match; 0 means that none of the bits need to match.  So a 255.255.255.0 mask ensures that only IP address between 192.168.16.0 and 192.168.16.255 are allowed -- the last 8 bits are allowed to change while the first three chunks are not.