I've entered the IP address from the Windows Azure Portal (both the one specified in the website Dashboard or within the Manage Domains area) but when trying to use SagePay Direct it returns that it is not a valid IP address.
I eventually solved this by doing a "showpost" for SagePay and then having to tell me what the IP address is.
The problem is - how can I determine this IP address for myself? As I worry that the IP address could change in the future.
If I use "Request.ServerVariables("LOCAL_ADDR")" (Classic ASP) it seems to return the local IP address of the webserver.