Introduction to ExternalDNS¶

In the previous sections, we had to manualy map a subdomain to a load balancer. Kubernetes ExternalDNS automates the creation, updation, and deletion of the Route 53 records.

ExternalDNS is a kubernetes tool that draws inspiration from kubernetes DNS and enhances resource discoverability through public DNS servers.

Unlike kubernetes' internal DNS server, KubeDNS, ExternalDNS does not act as a DNS server in itself. Instead, it leverages the kubernetes API to gather a comprehensive list of resources, such as Services and Ingresses, and then configures external DNS providers, like AWS Route 53 or Google Cloud DNS, to create the desired DNS records.

This functionality allows kubernetes resources to become readily accessible via public DNS servers, offering greater flexibility and integration for managing domain names in kubernetes environments.

ExternalDNS creates DNS records based on the host information. ExternalDNS sets up and manages records in Route 53 that point to controller deployed ALBs.

For ingress objects ExternalDNS will create a DNS record based on the hosts specified for the ingress object, as well as the external-dns.alpha.kubernetes.io/hostname annotation.

For services ExternalDNS will look for the annotation external-dns.alpha.kubernetes.io/hostname on the service and use the loadbalancer DNS to create Route 53 record.