IE 9, Cassini and the dreaded dns error (or page can’t load)

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So I’ve been hearing a lot of folks (myself included) having issue with debugging there web application with VS 2010, Cassini (the VS web server) and IE9.  It looks like this

Well I found and easy solution, image that .

Edit your hosts file at location c:\windows\system32\drivers\etc\hosts and make sure the localhost 127.0.0.1 line is uncommented and the localhost ::1 is commented or deleted.

You can ping locahost host from a command line and make sure you see

Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128

After that you should be in business.  The problems seem to come from the fact that IE9 starts to fast (Image that!!) for cassini and with localhost not setup properly (in Windows 7 by default it seems to be commented out) it causes this issue.

Let me know if this solves you problems (it worked on different machines I tried it on).

Cheers,

ET