Fiddler changes your proxy settings on startup and reverts them back to what they were before you started when Fiddler is closed.

However, that doesn't really explain your problem, because when Fiddler is running it will use your old proxy server as an upstream proxy, and when you shut it down, it reverts the settings back to what they were before.

If you don't want to use Fiddler with IE, uncheck the "Act as system proxy" checkbox inside Tools / Fiddler Options; note that you'll need to manually configure your application or framework (e.g. .NET) to use 127.0.0.1:8888 as a proxy though.

 fiddler这个软件启动时会加上http=127.0.0.1:8888;https=127.0.0.1:8888在代理中并启动，这相当改动了网络出口，

这时如果vpn是连接状态它就会断开，你重新连接就行了。

你在使用这个软件时，按照这样的顺序就没有问题，先启动fiddler在连接vpn。在关闭fiddler软件时它自动去掉代理，这时它又改变了网络出口，vpn就会断开，这时你重新连接一下就好了。