Here’s a nice gotcha you might want to think about. Vista ships with IP Version 6 and this may in some situations affect how IP Addresses are returned by your Web applications.

As part of my ASP.NET tools I have a request logging module that hooks into the pipeline and picks up and logs requests to a database as part of the application. One of the things that gets logged is the IP Address. Since for the longest time we could be reasonably sure of what constitutes an IP address with a length of 15 characters.

Well I just got bit by this fixed length as I was testing an application locally and realized that the log inserts where failing with the ever so friendly:

String or binary data would be truncated. The statement has been terminated.

Took a while to figure out why all of a sudden these calls where failing, but rest assured it’s the new IP6 address which looks something like this:

Request.UserHostAddress = "fe80::18ce:34b5:e7e6:dd8%12"

Somehow I suspect that’s not quite a valid result – certainly the %12 doesn’t look right (then again I’m still running Vista RC1).

There’s a lot more information available – this WikiPedia IP6 entry is helpful.

In any case – it’s important to remember that it’s possible that IP address are going to be quite a bit longer. It looks 39 (4  * 8 + 7 )  chars are going to be required to house a full IP6 address.

For the time being IP6 isn’t going to be an issue for servers, but on client Vista machines IP6 is enabled by default and so internally it’ll run through IP6 stack for localhost requests.

You can turn off IP6 – actually seems reasonable for the time being since most likely your routers and modems don’t support it anyway <s>…