N10-009 Question 232
Single answerRecord types: Address (A), AAAA, Canonical name (CNAME), Mail exchange (MX), Text (TXT), Nameserver (NS), Pointer (PTR)A company is moving its public website from an on-premises server to a cloud-hosted platform. The DNS administrator wants users to continue reaching the site by browsing to www.example.com, while also making it easier to repoint the web name in the future without changing multiple records. The cloud provider has instructed the administrator to point the web host name to webhost.cloudprovider.net. Which DNS record should the administrator create for www.example.com?
- A
Create an A record for www.example.com that points directly to the IPv4 address of webhost.cloudprovider.net
- B
Create a CNAME record for www.example.com that points to webhost.cloudprovider.net
- C
Create an MX record for www.example.com that points to webhost.cloudprovider.net
- D
Create a PTR record for www.example.com that points to webhost.cloudprovider.net
Show answer and explanation
Correct answer: B
Explanation
The best answer is to create a CNAME record for www.example.com pointing to webhost.cloudprovider.net. A CNAME is used when one DNS name should act as an alias for another DNS name. This is especially practical when a cloud or SaaS provider wants customers to reference a provider-managed hostname whose underlying IP addresses may change over time. By contrast, an A record maps a name directly to an IPv4 address, an AAAA record maps a name to an IPv6 address, an MX record is for email delivery, an NS record identifies authoritative name servers for a zone, a TXT record stores text-based DNS data such as SPF or domain-verification strings, and a PTR record supports reverse DNS lookups. As reflected in common DNS operational guidance and standards such as RFC 1034 and RFC 1035, CNAME records are appropriate for aliasing one hostname to another hostname in forward lookups.
- A. Incorrect.
This is incorrect for the stated goal. An A record maps a hostname to an IPv4 address, and it can work if you know and control the target IP. However, the scenario specifically says the provider instructed the administrator to point the name to another hostname and that the administrator wants easier future changes. A CNAME alias is designed for this use case because www.example.com can follow changes made to the target host's A or AAAA records without requiring separate updates.
- B. Correct.
This is correct. A CNAME (Canonical Name) record aliases one hostname to another hostname. In this scenario, www.example.com should resolve to webhost.cloudprovider.net, allowing the provider to manage the underlying A/AAAA records. This is a common best practice for cloud-hosted services when the vendor supplies a DNS name rather than a fixed IP address.
- C. Incorrect.
This is incorrect. An MX (Mail Exchange) record identifies the mail server responsible for accepting email for a domain. It is used for email routing, not for directing web traffic for a website hostname such as www.example.com.
- D. Incorrect.
This is incorrect. A PTR (Pointer) record is used for reverse DNS, mapping an IP address back to a hostname. It is commonly used for reverse lookups, such as validating mail server identity, but it does not direct clients browsing to a website hostname.