When setting up application links between JIRA and Confluence, the application link is automatically set to the base url, and after configuring can not be changed any more.
In the application link configuration screen it is possible to change the display url of the application link, but not the application url.
The display url should/could always be the base url, where as the application url should be adjustable to configure the local addresses on which the instances communicate with each other.
Used in test setup: Confluence 5.4.2 applinks 4.0.11