I have an old agent with IIS 7.5 and CA 12.0 sp3 cr9. One of the apps just got modified to use MVC framework and now giving 403s and 404s. I reconfigured the app to use integrated mode and rerun the agent configuration. While some pages are working not all are working.
IS MVC framework supported only after 12.52 sp1 because I have another app with 12.52 sp1 cr1 where MVC framework is working fine.
Refer this KB