Question

Difficulty: MediumDNS Infrastructure and Record Types

A network administrator is auditing enterprise DNS configurations. Match each DNS resource record type on the left with its correct functional description on the right.

  • CNAME RecordMaps an alias domain name to a canonical domain name rather than directly to an IP address.
  • MX RecordSpecifies the mail servers responsible for accepting incoming email messages on behalf of a domain, including priority values.
  • SRV RecordDefines the hostname, port number, priority, and weight for specific directory or communication services such as LDAP or SIP.
  • PTR RecordMaps an IP address back to a fully qualified domain name (FQDN) to enable reverse DNS lookups.

Answer

CNAME matches the alias-to-canonical domain description; MX matches the mail server routing description; SRV matches the service location (hostname, port, priority, weight) description; PTR matches the IP address-to-FQDN reverse lookup description.
Each DNS resource record fulfills a distinct network role: CNAME creates domain aliases; MX routes domain mail to designated email servers; SRV locates specific network services along with port and priority parameters; PTR performs reverse DNS lookups mapping IP addresses back to domain names.

Step-by-Step Solution

1
Analyze CNAME functionality
CNAME provides alias redirection from one FQDN to another canonical domain name.
Alias names simplify domain administration when multiple services map to a single target host.
2
Analyze MX functionality
MX records specify mail handling hosts along with preference ordering.
Mail delivery protocols query MX records to determine destination mail servers for email delivery.
3
Analyze SRV functionality
SRV records define target host, port, priority, and weight for specific network protocols.
Applications requiring discovery of host ports (like Active Directory LDAP or SIP VoIP) rely on SRV records.
4
Analyze PTR functionality
PTR records perform IP-to-hostname reverse mapping.
Reverse DNS lookup zones (in-addr.arpa) resolve IP addresses to domain names for auditing and security verification.

Key Concept

DNS Resource Record Functions and Infrastructure Roles
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