尝鲜，使用kubeadm部署了一套k8s 1.11
1master, 2node集群，按官方文档步骤操作，部署下来一路顺利，但最后测试dns解析时出问题了。

nslookup kuberenetes.default.svc.cluster.local 解析结果正常。
nslookup kubernetes.default 解析不出来结果。

环境信息：
操作系统centos 7.5， docker 1.13， k8s 1.11

NAME                          READY     STATUS    RESTARTS   AGE

coredns-78fcdf6894-zgvtt      1/1       Running   0          1d

etcd-cp0                      1/1       Running   0          1d

kube-apiserver-cp0            1/1       Running   0          1d

kube-controller-manager-cp0   1/1       Running   0          1d

kube-proxy-bkrb8              1/1       Running   0          1d                                  使用的iptables模式

kube-proxy-hp6hj              1/1       Running   0          1d

kube-proxy-sbl2v              1/1       Running   0          1d

kube-router-2bnmf             1/1       Running   1          1d

kube-router-8tq77             1/1       Running   1          1d

kube-router-c6pgj             1/1       Running   1          1d

kube-scheduler-cp0            1/1       Running   0          1d

# kubectl exec -ti busybox-7999f69f9d-b6zzf  -- /bin/sh

/ # nslookup kubernetes.default.svc.cluster.local

Server:         10.96.0.10

Address:        10.96.0.10:53



Name:   kubernetes.default.svc.cluster.local

Address: 10.96.0.1



*** Can't find kubernetes.default.svc.cluster.local: No answer



/ # nslookup kubernetes.default

Server:         10.96.0.10

Address:        10.96.0.10:53



** server can't find kubernetes.default: NXDOMAIN



*** Can't find kubernetes.default: No answer

*** Can't find kubernetes.default: No answer



/ # cat /etc/resolv.conf

nameserver 10.96.0.10

search default.svc.cluster.local svc.cluster.local cluster.local

options ndots:5

# k get ep kube-dns

NAME       ENDPOINTS                     AGE

kube-dns   10.244.1.2:53,10.244.1.2:53   1d

k describe svc kube-dns
Name:              kube-dns

Namespace:         kube-system

Labels:            k8s-app=kube-dns

               kubernetes.io/cluster-service=true

               kubernetes.io/name=KubeDNS

Annotations:       prometheus.io/port=9153

               prometheus.io/scrape=true

Selector:          k8s-app=kube-dns

Type:              ClusterIP

IP:                10.96.0.10

Port:              dns  53/UDP

TargetPort:        53/UDP

Endpoints:         10.244.1.2:53

Port:              dns-tcp  53/TCP

TargetPort:        53/TCP

Endpoints:         10.244.1.2:53

Session Affinity:  None

Events:            <none>

请教各位高手，哪儿出了问题，如何解决？