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Configure Conditional Forwarder with CoreDNS in EKS Cluster

by | Sep 3, 2021

Looking for tips to configure conditional forwarder with CoreDNS in the Amazon EKS cluster?

Worry not, Bobcares is here to help you out! Let’s take a quick look at the advice offered by the experts at Bobcares.

How do you configure a conditional forwarder with CoreDNS in the Amazon EKS cluster?

AWS allows customers to leverage the latest technologies to transform their business. Above all, with an extensive global cloud infrastructure, AWS is at the forefront of running enterprise applications. Although it offers several different features, challenges do pop up every now and then.

Fortunately, this is where Bobcares steps in to help you out. Also, you get access to experienced support tech. In conclusion, our support team is the go-to team for all AWS queries.

As a part of our AWS Support Services here, we often receive requests from customers to configure conditional forwarder with CoreDNS in the Amazon EKS cluster.

Let us now look at the steps that our Support Team follows to perform this task.

We can certainly use CoreDNS to configure conditional forwarding. In addition, CoreDNS is a general-purpose authoritative DNS server. It serves as cluster DNS, and complies with the DNS specifications.

Furthermore, CoreDNS is a modular and pluggable DNS server. Additionally, each plugin offers news functionality to CoreDNS.  Moreover, it is configured using a CoreDNS configuration file called Corefile.

Solving How to Configure Conditional Forwarder with CoreDNS in EKS Cluster

Interestingly, DNS can be launched using the addon manager since it is a built-in Kubernetes service. In other words, this involves sending DNS queries to domains resolved by a customized DNS server. Here is the solution offered by the experts at Bobcares.

  1. In Kubernetes, CoreDNS is installed with a default Corefile configuration. Initially, modify the CoreDNS ConfigMap. Then add the conditional forwarder

$ kubectl -n kube-system edit configmap coredns

As a result, you will see the following output:

apiVersion: v1

kind: ConfigMap



labels: coredns

k8s-app: kube-dns

name: coredns

namespace: kube-system


Corefile: |

. : 53 {



kubernetes cluster.local {

pods insecure



prometheus :9153

forward ./etc/resolv.conf

cache 30

forward . custom-dns-server




domain-name : 53 {


cache 30

forward . custom-dns-server



Once you have gotten this output, it is time to move on to the next step.

2. After that, check that domain name resolution works:

$ kubectl run busybox –restart=Never –image=busybox: 1.28 — sleep 3600

$ kubectl exec busybox — nslookup domain-name

To clarify, here we need to replace domain-name and custom-dns-server with the domain name and custom DNS server IP address respectively.

Need assistance with EKS? AWS Support Services is just a click away! In other words, our support services are well-versed with different challenges put forth by AWS.


In conclusion, this easy fix comes via our Support Techs. At Bobcares, we are glad to be of service to our customers with any inquiry related to EKS and beyond.


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