Xbox Updates: Regex Rescue
For some time now, keeping Fiddler active while downloading system updates has resulted in the CDN domains resolving as IP addresses, which returns a 404 error. To address this issue, a simple bit of regex + AutoResponder can fix this:
In my case, I have the following rules setup for each available CDN:
Alternatively, if you'd like a catch-all rule for any IP addresses instead:
regex:http://[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+
http://d1.xboxlive.com
One word of caution though: This will absolutely eat all of your available ram as Fiddler uses as much memory as it needs to hold the traffic it displays. You can tweak this pretty easily with the Keep: All Sessions button to your liking/memory availability.