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.
There is already a CNAME (Alias) associated with mail.contoso.com which points to Server1.contoso.com
Record Name Record Type Data
Contoso.com Mail Exchanger (MX) [20] mail2.contoso.com
Mail2 Alias CNAME Server2.contoso.com