BeginnerPhone
2 min
NAT vs PAT
NetworkingIPv4NAT
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Interview Question
What is the difference between NAT and PAT, and where would you use each?
Key Points to Cover
- NAT maps one IP to another; PAT maps many internal hosts to one IP using ports
- PAT conserves IPv4 addresses for outbound internet access
- Static/1:1 NAT for publishing internal services
Evaluation Rubric
Defines NAT accurately34% weight
Explains PAT and port multiplexing33% weight
Gives correct usage scenarios33% weight
Hints
- 💡PAT is sometimes called NAT overload.
Common Pitfalls to Avoid
- ⚠️Confusing PAT as entirely separate from NAT, rather than a specific type of NAT (NAPT/NAT Overload).
- ⚠️Failing to clearly articulate that port numbers are the distinguishing factor that allows PAT to support many-to-one mappings.
- ⚠️Not emphasizing the crucial role of PAT in conserving public IPv4 addresses for outbound internet access.
- ⚠️Inaccurately describing use cases, such as suggesting PAT for direct external access to internal servers instead of Static NAT.
- ⚠️Not providing a clear distinction between Static NAT (one-to-one) and PAT (many-to-one).
Potential Follow-up Questions
- ❓How does port exhaustion manifest?
- ❓How does NAT affect inbound connections?
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