How to DNS in Rancher?

Hi folks, I’m new to Rancher and Docker in general so I’m sorry if this is an obvious question. What are the patterns for accessing services by hostname or FQDN from external sources? I have a DNS server that serves the local (external) network and I have no idea how to connect it to Rancher. I have a DNS entry for the host, but I’d prefer to have some way of doing http://service.localdomain:80 no matter what the internal port is, and to have it automated. How would that work in a cluster? What about a mixed windows linux cluster?