In Fiddler and later, you can force Fiddler to issue all requests from a particular network interface (rather than the default). To do so, you need to set a new preference in Fiddler with the IP address of that interface. Use the QuickExec box to set the IP:

prefs set

You can remove the current preference setting by typing:

prefs remove

You can view the current preference settings by typing:

prefs show


  • You need to clear the session list (hit CTRL+X) to clear out any cached upstream sockets that may be using the other interface.
  • If you are configured to use an upstream gateway/proxy server, you must ensure that that proxy server is accessible from the specified network interface. For instance, if you specify the egress.IP to point to your Cell network, but have Fiddler configured to use your LAN proxy as a gateway, it's likely that all requests will fail (HTTP/502) because your proxy gateway is unreachable from your Cellular network.

You can show information about what outbound egress endpoint is used for a given request using the following FiddlerScript

static function OnBeforeResponse(oSession: Session)
if ((null != oSession.oResponse.pipeServer) && (null != oSession.oResponse.pipeServer.GetRawSocket())){
    oSession["ui-customcolumn"] = oSession.oResponse.pipeServer.GetRawSocket().LocalEndPoint.ToString();
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