I have found a file in coredns volume called Corefile. In this file forwarding DNS is hard coded to google dns servers. root@vpn-server:/var/lib/docker/volumes/opt_dnsconfig/_data# cat Corefile . { reload 15s hosts /root/dnsconfig/netmaker.hosts { fallthrough } forward . 8.8.8.8 8.8.4.4 log }