You have an Office 365 tenant that uses an Enterprise E3 subscription. You have two servers in a
perimeter network that have the Active Directory Federation Services (AD FS) proxy role service
installed. A federation server farm is located behind a firewall.
You need to ensure that the AD FS proxies can communicate with the federation server farm.
Which two name resolution strategies can you use? Each correct answer presents a complete
solution.

A.
HOSTS file on the proxy servers

B.
DNS server in the perimeter network

C.
LMHOSTS file on the proxy servers

D.
LMHOSTS file on the federation servers

E.
HOSTS file on the federation servers

Explanation:
Configure Name Resolution for a Federation Server Proxy in a DNS Zone That Serves Only the
Perimeter Network
So that name resolution can work successfully for a federation server in an Active Directory
Federation Services (AD FS) scenario in which one or more Domain Name System (DNS) zones serve
only the perimeter network, the following tasks must be completed:
* The hosts file on the federation server proxy must be updated to add the IP address of a federation
server.
* DNS in the perimeter network must be configured to resolve all client requests for the AD FS host
name to the federation server proxy. To do this, you add a host (A) resource record to perimeter
DNS for the federation server proxy.

Configure Name Resolution for a Federation Server Proxy in a DNS Zone That Serves Only the
Perimeter Network
https://technet.microsoft.com/en-us/library/dd807045.aspx