How to get elmah.io to resolve the correct client IP

elmah.io try to resolve the IP of the client causing a log message, no matter what severity (Error, Information, etc.) and platform (browser, web-server, etc.) a log message is sent from. This is done by looking at multiple pieces of information provided by the sender. In some cases, elmah.io may not be able to resolve the IP or resolves a wrong IP address. In this document, you will find help getting the right client IP into elmah.io.

Missing IP when using a proxy

If you are using a proxy layer in between the client and your web server, you may experience log messages without a client IP. This is probably caused by the proxy hiding the original IP from your web server. Most proxies offer an alternative server variable like the X-Forwarded-For header. You can inspect the server variables on the Server Variables tab on elmah.io and check if your proxy includes the original IP in any of the variables. We support custom headers from a range of proxies (like Cloudflare). Most proxies support some kind of settings area where the X-Forwarded-For header can be enabled. If you are using a proxy that uses custom headers, please make sure to reach out and we may want to include the custom header to elmah.io.

Wrong IP when using a proxy

If the client IP is wrong when behind a proxy, it is typically because the proxy replaces the client IP when calling your server with the IP of its own server. This is a poor practice and makes it very hard for elmah.io to figure out which IP belongs to the user and which one to the proxy. Luckily, this is configurable in a lot of proxies through their settings area.

Missing IP

This can be caused by a number of issues. In most instances, the client doesn't include any server variables that reveal the IP address. In this case, the client IP will not be available within the elmah.io UI. In some cases, you may know the user's IP from session variables or similar. To include an IP on messages logged to elmah.io, you can implement the OnMessage event or action, depending on which integration you are using. In this example, we use the OnMessage event on the Elmah.Io.Client package to include the user's IP manually:

var userIp = "1.1.1.1"; // <-- just for the demo
var client = ElmahioAPI.Create("API_KEY");
client.Messages.OnMessage += (sender, args) =>
{
    var message = args.Message;
    if (message.ServerVariables == null) message.ServerVariables = new List<Item>();
    message.ServerVariables.Add(new Item("X-FORWARDED-FOR", userIp));
};


This article was brought to you by the elmah.io team. elmah.io is the best error management system for .NET web applications. We monitor your website, alert you when errors start happening and help you fix errors fast.

See how we can help you monitor your website for crashes Monitor your website