DNS issues for pods


I’ve just started with Kubernetes in Rancher and I have some issues.
I could see that the Kube-dns service is up and running, but the only pod that is able to perform external domain is kube-dns.
I’ve created more pods and all set to use the service IP for DNS, but all of them are not able to perform external dns resolving.
I saw that on Kubenetes 1.6 they’ve added the configmap for DNS where I can set upstreamNameServers, but in Kubernetes 1.5.1 it is not supported.

Can you assist me please on this?