Adds docs.

docs/guides/troubleshoot-dns.md

@@ -0,0 +1,20 @@
+# Troubleshoot DNS
+
+If DNS resolution isn't working properly:
+
+1. Check CoreDNS status:
+   ```bash
+   kubectl get pods -n kube-system -l k8s-app=kube-dns
+   kubectl logs -l k8s-app=kube-dns -n kube-system
+   ```
+
+2. Verify CoreDNS configuration:
+   ```bash
+   kubectl get configmap -n kube-system coredns -o yaml
+   ```
+
+3. Test DNS resolution from inside the cluster:
+   ```bash
+   kubectl run -i --tty --rm debug --image=busybox --restart=Never -- nslookup kubernetes.default
+   ```
+