If you have installed the Exchange 2010 MP and consistently get the following alert triggering:-
KHI: HTTP Connectivity with Autodiscover – RPC Client Access failure (Logon)
This might be because your you have Outlook Anywhere enabled on your CAS servers but not all of them are external facing (exposed to the internet). On the CAS boxes that have Outlook Anywhere installed but are not external facing do the following:-
Create the following DWORD registry value:
Value Name: EnablePreferredSiteEnforcement
Data Type: REG_DWORD
Note:- After you set the EnablePreferredSiteEnforcement value to 0, a CAS server will accept connection requests from any site and not try to redirect the request to a different server.
After implementing this the alert self healed !