How to expose kube-dns service for queries outside cluster?

Question

I\'m trying to expose the \"kube-dns\" service to be available to be queried outside of the Kubernetes cluster. In order to do this I edited the \"Service\" definition to ch

Answer 1

Are you querying on the tcp port or the udp port?

I changed my kube-dns to be a NodePort service:

$ kubectl describe services kube-dns --namespace kube-system
Name:           kube-dns
Namespace:      kube-system
Labels:         k8s-app=kube-dns
            kubernetes.io/cluster-service=true
            kubernetes.io/name=KubeDNS
Selector:       k8s-app=kube-dns
Type:           NodePort
IP:         10.171.240.10
Port:           dns 53/UDP
NodePort:       dns 30100/UDP
Endpoints:      10.168.0.6:53
Port:           dns-tcp 53/TCP
NodePort:       dns-tcp 30490/TCP
Endpoints:      10.168.0.6:53
Session Affinity:   None

and then queried on the udp port from outside of the cluster and everything appeared to work:

$ dig -p 30100 @10.240.0.4 kubernetes.default.svc.cluster.local

; <<>> DiG 9.9.5-9+deb8u6-Debian <<>> -p 30100 @10.240.0.4 kubernetes.default.svc.cluster.local
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45472
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;kubernetes.default.svc.cluster.local. IN A

;; ANSWER SECTION:
kubernetes.default.svc.cluster.local. 30 IN A   10.171.240.1

;; Query time: 3 msec
;; SERVER: 10.240.0.4#30100(10.240.0.4)
;; WHEN: Thu May 26 18:27:32 UTC 2016
;; MSG SIZE  rcvd: 70

Right now, Kubernetes does not allow NodePort services to share the same port for tcp & udp (see Issue #20092). That makes this a little funky for something like DNS.

EDIT: The bug was fixed in Kubernetes 1.3.