APM AD Auth and Trusted Domains

Hi there,

 

I have a domain trust between acme.com and contoso.com. The APM lives in the acme.com and can authenticate users against this domain using AD Auth. With the trust in place I want to allow users in the contoso domain to authenticate through the APM.

 

AAA AD server is configured for acme.com AAA AD Trusted Domain is configured for contoso.com with acme.com AAA selected and configured as the Root.

 

In the VPE the AD Auth is pointing to acme.com with cross domain support enabled. The trusted domains is grayed out.

 

What am I missing?