Your company has a main office site and a disaster recovery site. The two sites connect to each other
by using redundant WAN links. Each site connects directly to the Internet. Each site contains one
Exchange Server 2013 server that is accessible from the Internet. The company uses the
©contoso.com email address suffix. The DNS records that can be resolved from the Internet are
configured as shown in the following table.

When the Internet link at the main office site fails, the company cannot receive incoming email from
the Internet. You need to ensure that incoming email from the Internet is delivered to Server1.
Incoming email from the Internet must be delivered to Server2 if Server1 is unavailable. What should
you create?

A.
A CNAME record for the name mail.contoso.com that resolves to server2.contoso.com

B.
An MX record that has a cost of 20 and resolves to mail.contoso.com

C.
An MX record that has a cost of 20 and resolves to server2.contoso.com

D.
An A record for the name mail.contoso.com that resolves to 131.107.101.1

Explanation:
CNAME record
A CNAME record is an abbreviation for Canonical Name record and is a type of resource record in the
Domain Name System (DNS) that specifies that the domain name is an alias of another, canonical
domain name. Here “canonical” usually means: a more generally accepted or standard name.
For example, if there is a DNS zone as follows:
NAME TYPE VALUE
————————————————–
bar.example.com. CNAME foo.example.com.
foo.example.com. A 192.0.2.23

MX record
A mail exchanger record (MX record) is a type of resource record in the Domain Name System that
specifies a mail server responsible for accepting email messages on behalf of a recipient’s domain,
and a preference value used to prioritize mail delivery if multiple mail servers are available. The set
of MX records of a domain name specifies how email should be routed with the Simple Mail Transfer
Protocol (SMTP).
A Record
An A (address) record is a DNS record that can be used to point your domain name and host names
to a static IP address.
NOT A B D
Need to increase the cost associated with the MX record of Server2 so that Server1 is preferred over
Server2 but Server2 will be used if Server1 is not available.
C
Need to increase the cost associated with the MX record of Server2 so that Server1 is preferred over
Server2 but Server2 will be used if Server1 is not available.