I have created self managed kubernetes cluster in Digital Ocean. But the core DNS failed to resolve the FQDN of any components. While going through the blog , I found out that there is an issue in Digital Ocean private ip routing. Can anyone please help me resolve this issue.
root@kubernetes-master:~# kubectl run -i --tty --rm dns-test --image=busybox --restart=Never -- sh
If you don't see a command prompt, try pressing enter.
/ # nslookup kubernetes.deault
;; connection timed out; no servers could be reached
/ # nslookup kubernetes.deault
;; connection timed out; no servers could be reached
/ # ^C
/ # exit
pod "dns-test" deleted
pod default/dns-test terminated (Error)
root@kubernetes-master:~# kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
default myapplication-74ff95cf4f-mjqmz 0/1 CrashLoopBackOff 9 (4m41s ago) 40m
default postgres-0 1/1 Running 0 119m
kube-flannel kube-flannel-ds-6tw5c 1/1 Running 2 (24h ago) 24h
kube-flannel kube-flannel-ds-k9g6t 1/1 Running 2 (24h ago) 24h
kube-system coredns-55cb58b774-4t7d6 1/1 Running 2 (24h ago) 24h
kube-system coredns-55cb58b774-qdmgb 1/1 Running 2 (24h ago) 24h
kube-system etcd-kubernetes-master 1/1 Running 2 (24h ago) 24h
kube-system kube-apiserver-kubernetes-master 1/1 Running 2 (24h ago) 24h
kube-system kube-controller-manager-kubernetes-master 1/1 Running 2 (24h ago) 24h
kube-system kube-proxy-5lrdr 1/1 Running 2 (24h ago) 24h
kube-system kube-proxy-vbnhx 1/1 Running 2 (24h ago) 24h
kube-system kube-scheduler-kubernetes-master 1/1 Running 2 (24h ago) 24h
root@kubernetes-master:~#
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Hey!
As far as I can see your CoreDNS pods are running, but DNS queries fail which is probably due to missing firewall rules or Flannel misconfiguration.
You need to make sure UDP ports 53, 8472, and 8285 are open between nodes in your DigitalOcean firewall or Droplet firewall, depending on what you’ve configured.
Also, I can see that you are using Flannel, so it should be set to use the private interface (usually eth1). And double-check that your CoreDNS config has valid upstreams.
Also in the output you shared, your DNS test has a typo (deault instead of default), that could confuse things too.
- Bobby
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