Integrating OpenShift CoreDNS with Active Directory DNS

Integrating OpenShift CoreDNS with Active Directory (AD) enables your OpenShift cluster to resolve DNS records from your AD-managed domain. This article walks through the steps to configure CoreDNS to forward DNS queries to your AD DNS server.

Prerequisites

• OpenShift cluster with CoreDNS.
• Active Directory DNS server (e.g., 192.168.1.10 for domain example.local).
• OpenShift nodes must be able to reach the AD DNS server.

Steps to Configure CoreDNS for AD Integration

• Edit the CoreDNS ConfigMap

oc edit configmap coredns -n openshift-dns

• Modify the CoreDNS ConfigFile

. {
  forward . 8.8.8.8 8.8.4.4     # External DNS (Google DNS)
  forward . 192.168.1.10       # AD DNS server
  cache 300                    # Cache TTL for external queries (5 minutes)
  log                          # Enable logging
  metrics                      # Enable Prometheus metrics
  health                       # Enable health check
}

example.local:53 {
  forward . 192.168.1.10       # Forward queries for example.local to AD DNS
  cache 600                    # Cache TTL for AD domain queries (10 minutes)
  log                          # Log queries for example.local
}

• Apply the Configuration

oc delete pod -n openshift-dns --all

• Test DNS Resolution

oc run -i --tty --rm debug --image=busybox --restart=Never -- nslookup myhost.example.local

• Monitor and Troubleshoot

oc logs -n openshift-dns <coredns-pod-name>

curl http://<coredns-pod-ip>:9180/health

Metrics: Monitor DNS metrics via Prometheus

Conclusion

By configuring CoreDNS to forward DNS queries to your AD DNS server, you enable your OpenShift cluster to resolve AD-managed domain records. With CoreDNS's caching, logging, metrics, and health checks, you can optimize DNS resolution and ensure a reliable DNS setup.