add docs

README.md

@@ -190,6 +190,14 @@ $ kubectl annotate service nginx "external-dns.alpha.kubernetes.io/ttl=10"
 
 For more details on configuring TTL, see [here](docs/ttl.md).
 
+Use the internal-hostname annotation to create DNS records with ClusterIP as the target.
+
+```console
+$ kubectl annotate service nginx "external-dns.alpha.kubernetes.io/internal-hostname=nginx.internal.example.org."
+```
+
+If the service is not of type Loadbalancer you need the --publish-internal-services flag.
+
 Locally run a single sync loop of ExternalDNS.
 
 ```console

docs/contributing/getting-started.md

@@ -8,7 +8,7 @@ You can build ExternalDNS for your platform with `make build`, you may have to i
 
 ExternalDNS's sources of DNS records live in package [source](../../source). They implement the `Source` interface that has a single method `Endpoints` which returns the represented source's objects converted to `Endpoints`. Endpoints are just a tuple of DNS name and target where target can be an IP or another hostname.
 
-For example, the `ServiceSource` returns all Services converted to `Endpoints` where the hostname is the value of the `external-dns.alpha.kubernetes.io/hostname` annotation and the target is the IP of the load balancer.
+For example, the `ServiceSource` returns all Services converted to `Endpoints` where the hostname is the value of the `external-dns.alpha.kubernetes.io/hostname` annotation and the target is the IP of the load balancer or where the hostname is the value of the `external-dns.alpha.kubernetes.io/internal-hostname` annotation and the target is the IP of the service CLusterIP.
 
 This list of endpoints is passed to the [Plan](../../plan) which determines the difference between the current DNS records and the desired list of `Endpoints`.
 

docs/faq.md

@@ -57,7 +57,7 @@ Services exposed via `type=LoadBalancer`, `type=ExternalName` and for the hostna
 
 There are three sources of information for ExternalDNS to decide on DNS name. ExternalDNS will pick one in order as listed below:
 
-1. For ingress objects ExternalDNS will create a DNS record based on the host specified for the ingress object. For services ExternalDNS will look for the annotation `external-dns.alpha.kubernetes.io/hostname` on the service and use the corresponding value.
+1. For ingress objects ExternalDNS will create a DNS record based on the host specified for the ingress object. For services ExternalDNS will look for the annotation `external-dns.alpha.kubernetes.io/hostname` on the service and use the loadbalancer IP, it also will look for the annotation `external-dns.alpha.kubernetes.io/internal-hostname` on the service and use the service IP.
 
 2. If compatibility mode is enabled (e.g. `--compatibility={mate,molecule}` flag), External DNS will parse annotations used by Zalando/Mate, wearemolecule/route53-kubernetes. Compatibility mode with Kops DNS Controller is planned to be added in the future.
 
@@ -272,7 +272,7 @@ Separate them by `,`.
 
 ### Are there official Docker images provided?
 
-When we tag a new release, we push a Docker image on Zalando's public Docker registry with the following name: 
+When we tag a new release, we push a Docker image on Zalando's public Docker registry with the following name:
 
 ```
 registry.opensource.zalan.do/teapot/external-dns