In IIS you can declare the mime type for WOFF2 font files by adding the following to your project's web.config:
<system.webServer>
<staticContent>
<remove fileExtension=".woff2" />
<mimeMap fileExtension=".woff2" mimeType="font/woff2" />
</staticContent>
</system.webServer>
Update:
The mime type may be changing according to the latest W3C Editor's Draft WOFF2 spec. See Appendix A: Internet Media Type Registration section 6.5. WOFF 2.0 which states the latest proposed format is font/woff2