Troubleshooting · DNS
DNS resolution failure
Names fail to resolve, resolve inconsistently, or return unexpected addresses.
Work through these in order
- 01
Identify the resolver in use
Confirm which servers the client is configured with, domain members must use internal DNS.
- 02
Query the authoritative server directly
Compare an authoritative answer with the recursive answer to isolate caching problems.
- 03
Check the record
Correct type and value, appropriate TTL, and no conflicting CNAME at the same label.
- 04
Check split horizon consistency
Internal and external zones drifting apart is a frequent cause of 'works from home only' reports.
- 05
Check for stale cache
Client cache, resolver cache and long TTLs after a change all produce the same symptom.
- 06
Check forwarders and conditional forwarders
A failed forwarder produces partial resolution that looks random.
Background reading
DNS
The Domain Name System is the distributed, hierarchical directory that resolves names to addresses and service records for nearly every other service.
Active Directory
Microsoft's on premises directory service, providing authentication, authorisation, policy and object management for Windows environments.
DHCP
Dynamic Host Configuration Protocol automatically issues IP addresses and network configuration to clients as they join a network.