Install Rancher on a cloud such as AWS, may happens DNS problem. Even with Rancher server and Rancher nodes.
The solution is set a docker daemon and restart docker:
How to check DNS on CentOS
$ cat /var/log/messages | grep dnsmasq
$ ps -ef | grep dnsmasq
Find IP and set to docker daemon
$ sudo vim /etc/docker/daemon.json
$ sudo systemctl restart docker