You should file a support ticket, because when you do a trace you only get the IP of the Mendix load balancer. Do be aware that the IP might change when you restart your app. It would be nice if the IP address could be locked to a node.
Friso, you need the ip of your appnode. See this question. You can get this one by setting up a ssh session in putty and doing this in your putty console:
curl -s icanhazip.com
The ip you will receive is your appnode ip.