fix: clarify that certain Pod A records are only available with CoreDNS

related to kubernetes/dns#633

Author: davidxia

content/en/docs/concepts/services-networking/dns-pod-service.md

@@ -107,7 +107,8 @@ and the domain name for your cluster is `cluster.local`, then the Pod has a DNS
 
 `172-17-0-3.default.pod.cluster.local`.
 
-Any Pods exposed by a Service have the following DNS resolution available:
+If you're using [CoreDNS], Pods exposed by a Service will also have the following
+DNS resolution available:
 
 `pod-ipv4-address.service-name.my-namespace.svc.cluster-domain.example`.
 
@@ -363,3 +364,5 @@ this problem.
 
 For guidance on administering DNS configurations, check
 [Configure DNS Service](/docs/tasks/administer-cluster/dns-custom-nameservers/)
+
+[CoreDNS]: /docs/tasks/administer-cluster/coredns/