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Symptoms: DNS Split-Horizon Confusion

  • Internal application order-svc on host app-node-03 (10.100.5.18) fails to connect to payments.acme.com with connection timeouts.
  • External users can reach payments.acme.com without any issues.
  • From app-node-03, curl https://payments.acme.com/health times out after 30 seconds.
  • A developer noticed that dig payments.acme.com from app-node-03 returns 203.0.113.50 (the external/public IP), not the internal IP 10.100.8.30.
  • The internal firewall does not permit internal hosts to connect to the external IP range 203.0.113.0/24 and back through NAT.
  • The DNS team recently consolidated internal and external zones and may have missed some records.
  • Other internal services (e.g., inventory.acme.com) resolve correctly to internal IPs from the same host.