In my web site, I created a map with ALK Maps, I display the points (Markers) and roads (routings) and all this works fine in Firefox and Chrome, but in IE I display the map
We were also running into this issue and the problem was the target URL was exceeding the maximum length of ~2,000 characters in IE11.
I agree with @user145400 that if it works in Chrome and Firefox it is very likely that CORS is already correctly enabled.