Forcing fiddler to use specific outgoing IP (programmatically)

[Carlos]

Hello Fiddler gang

Found this old post https://stackoverflow.com/questions/43898449/in-fiddler-is-it-possible-to-spoof-the-client-ip-address while trying to find out if there is a way of dynamically directing fiddler to send the requests thru specific IP address (I have a server with multiple IPs).

It suggest using X-EgreesIP so in my fiddler script I added:

oSession["X-EgreesIP"] = "10.10.10.123";

in my InBeforeRequest function but it doesn't seems to have any effect? by running netstat -f it still shows the main IP for establishing the connections to the remote host servers.

The same old post points to another link http://fiddler.wikidot.com/egressip where it mention that it can be configured by command but that means then ALL my requests will go thru that other configured IP, I want to programmatically be able to give a different IP based on the particular request.  Is that at all possible?

Thanks!

[Nick Iliev]

Hello Carlos,

 

Yes, the way to go is to direct all requests by setting the egress explicitly through the prefs option and not through a session flag.

prefs set fiddler.network.egress.IP 131.107.0.111

There is no option to modify the IP of origin for a specific request (e.g. to spoof the IP).

 

Regards,
Nick Iliev
Progress Telerik

[Carlos]

Thanks Nick .. I don't want to spoof IPs, my server has multiple public IPs (4 real ones).  I understand the original question in the old thread I linked is asking about spoofing but that's not what I'm trying to do.

I saw Eric mentioned X-Egress IP and specifically saying "If your machine has multiple NICs, Fiddler can direct the second request to egress via a specific IP address using the X-EgreesIP", that lead me to believe it was possible which is why I posted the question here.

Are you positive there is no such X-EgressIP flag?

 

[Nick Iliev]

There are no X-EgressIP or X-EgreesIP flags.

The following (and many more) are available:

Flag Name: x-ClientIP
Explanation: Set by Fiddler, this flag contains the IP address of the client that issued the request. Typically, this will be the current PC’s IP address, unless remote connections have been permitted using the option in the Fiddler Options > Connections tab.

Flag Name: x-HostIP
Explanation: Set by Fiddler, this flag contains the IP address of the server to which this request was sent.

Flag Name: x-OriginalURL
Explanation: Set by the AutoResponder, this flag contains the original request URL in the event that the URL was changed by an AutoResponder rule.

Flag Name: X-EgressPort
Explanation: Set by Fiddler, this flag contains the local port number used to establish the connection to the server or gateway proxy.

[Carlos]

Thanks @Nick .. for a moment I thought there was some hope .. oh well .. :-)