Rancher 1.6 Docs

DNS Service

Rancher provides an infrastructure service for a distributed DNS service by using its own lightweight DNS server coupled with a highly available control plane. Each healthy container is automatically added to the DNS service when linked to another service or added to a Service Alias. When queried by the service name, the DNS service returns a randomized list of IP addresses of the healthy containers implementing that service.

• By default, all services within the same stack are added to the DNS service without requiring explicit service links, which can be set under Service Links in a service.
• You can resolve containers within the same stacks by the service names.
• If you need a custom DNS name for your service, that is different from your service name, you will be required to set a link to get the custom DNS name.
• Links are still required if a Service Alias is used.
• To make services resolvable that are in different stacks, you can use <service_name>.<stack_name> and are not required explicit links, which can be set under Service Links in a service.

Because Rancher’s overlay networking provides each container with a distinct IP address, you do not need to deal with port mappings and do not need to handle situations like duplicated services listening on different ports. As a result, a simple DNS service is adequate for handling service discovery.

Learn more about the internal DNS service for Cattle environments and Kubernetes environments.