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What is split-brain (or split-horizon) DNS?

Split-brain DNS (split-horizon) returns different answers based on who is asking:

Internal queries: Users inside your network see internal IP addresses.

External queries: Users on the internet see public IP addresses.

How it works:

Internal DNS servers have one set of records

External/public DNS has different records

Query source determines which answer you get

Use cases:

Internal servers accessible directly inside network

Same hostnames resolve differently by location

Can improve performance and security

Complexity: Requires maintaining two sets of records. Can cause confusion when troubleshooting.

Different docking instructions for local harbor traffic versus ships arriving from open sea.