Rancher implements a distributed DNS service by using its own light-weight 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.
<service_name>.<stack_name> and are not required explicit links.
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.