Name resolution from windows pods does not work on 1.18.1
FYI. Kubernetes 1.18.1 has a bug for windows nodes which fail to create network called Host on reboot. (https://github.com/kubernetes-sigs/sig-windows-tools/issues/52). As a result communication is broken within flannel even if you recreate network manually with docker network create -d nat host. To make DNS resolution to work again you also need to restart Rancher wins service get-service rancher-wins | Restart-ServiceComplete solution untill this is fixed is to modify StartKubelet.ps1 file and add following to it on line 3
$netId = docker network ls -f name=host --format "{{ .ID }}"if ($netId.Length -lt 1) { docker network create -d nat host}