Question

How to "fix server can't find external_domain: SERVFAIL" inside pod

Hello! I am using DO managed Kubernetes and I’ve met the following problem: My services try to send a request to sgx.geodatenzentrum.de but instead of a response, my service gets an error. Here is nslookup output:

nslookup sgx.geodatenzentrum.de
Server: 10.245.0.10
Address: 10.245.0.10:53
Non-authoritative answer:
Name: sgx.geodatenzentrum.de
Address: 141.74.48.40
** server can't find sgx.geodatenzentrum.de: SERVFAIL

Then I tested this domain on my own laptop and everything was fine:

nslookup sgx.geodatenzentrum.de
Server: 8.8.8.8
Address: 8.8.8.8#53
Non-authoritative answer:
Name: sgx.geodatenzentrum.de
Address: 141.74.48.40

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Bobby Iliev
Site Moderator
Site Moderator badge
August 25, 2023

Hi there,

The DigitalOcean Kubernetes uses CoreDNS for cluster DNS management.

I could suggest a couple of things here:

  1. Check the logs of the CoreDNS pods to see if there’s any specific error or warning that might indicate what’s going wrong. You can do this with:

    kubectl -n kube-system logs -l k8s-app=kube-dns
    
  2. Sometimes, simply restarting the CoreDNS pods can solve transient issues. You can do this with:

    kubectl -n kube-system rollout restart deployment coredns
    
  3. You can view the CoreDNS settings used by DOKS in the CoreDNS’s configuration file using the following command:

kubectl get configmap -n kube-system coredns -o yaml

Also for more informaiton on how to customize the CoreDNS settings, I could suggest the following guide:

https://docs.digitalocean.com/products/kubernetes/how-to/customize-coredns/

Best,

Bobby

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