BeginnerPhone
2 min
DNS A Record vs CNAME
DNSNetworkingWeb
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Interview Question
What is the difference between an A record and a CNAME record in DNS, and when would you use each?
Key Points to Cover
- A record maps a name to an IPv4 address
- CNAME maps a name to another canonical name
- Use CNAME for aliasing; A for direct address; apex usually requires A/ALIAS
Evaluation Rubric
Defines A record correctly34% weight
Defines CNAME and purpose33% weight
Gives valid usage constraints (apex)33% weight
Hints
- 💡Some DNS providers offer ALIAS/ANAME for apex CNAME-like behavior.
Common Pitfalls to Avoid
- ⚠️Confusing the direction of mapping (e.g., an A record maps an IP to a name instead of a name to an IP).
- ⚠️Failing to mention the critical limitation of CNAMEs at the domain's apex (root domain).
- ⚠️Not clearly articulating the 'when to use each' aspect with practical examples.
- ⚠️Omitting the concept of 'ALIAS' or 'ANAME' records as a common solution for apex aliasing where CNAMEs are restricted.
- ⚠️Providing overly simplistic definitions without explaining the underlying lookup process for CNAMEs.
Potential Follow-up Questions
- ❓What about AAAA records?
- ❓How do TTLs impact failover?
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