DNS Configuration for Inter PLMN FQDN Resoultion

The following sections describe how to configure DNS Server for Inter PLMN FQDN resolution. The steps are as follows:

Kubernetes Coredns configuration to route to external DNS

1. Execute the following command to edit k8s coredns configmap with external DNS Server to resolve FQDN not part of k8s cluster.

   kubectl -n kube-system edit configmap coredns

2. Add below to cordns configmap where domain.com is plmn domain.

   
   domain.com:53 {
   errors
   cache 30
   forward .  dns-serverip
   }

   Sample coredns configmap file:

   
   apiVersion: v1
   data:
     Corefile: |
       .:53 {
           errors
           health
           ready
           kubernetes nike in-addr.arpa ip6.arpa {
             pods insecure
             upstream /etc/resolv.conf
             fallthrough in-addr.arpa ip6.arpa
           }
           prometheus :9153
           forward . /etc/resolv.conf {
             prefer_udp
           }
           cache 30
           loop
           reload
           loadbalance
       }
       domain.com:53 {
           errors
           cache 30
           forward .  10.75.121.11
       }
   kind: ConfigMap
   metadata:
     annotations:
       kubectl.kubernetes.io/last-applied-configuration: |
         {"apiVersion":"v1","data":{"Corefile":".:53 {\n    errors\n    health\n    ready\n    kubernetes nike in-addr.arpa ip6.arpa {\n      pods insecure\n      upstream /etc/resolv.conf\n      fallthrough in-addr.arpa ip6.arpa\n    }\n    prometheus :9153\n    forward . /etc/resolv.conf {\n      prefer_udp\n    }\n    cache 30\n    loop\n    reload\n    loadbalance\n}\n"},"kind":"ConfigMap","metadata":{"annotations":{},"labels":{"addonmanager.kubernetes.io/mode":"EnsureExists"},"name":"coredns","namespace":"kube-system"}}
     creationTimestamp: "2020-05-27T18:43:13Z"
     labels:
       addonmanager.kubernetes.io/mode: EnsureExists
     name: coredns
     namespace: kube-system
     resourceVersion: "1314"
     selfLink: /api/v1/namespaces/kube-system/configmaps/coredns
     uid: 63a51c75-6b40-4dbb-b45e-30a22788097f