Hi, I'm currently fiddling with Docker Swarm on three sandbox servers running CentOS 7. Unfortunately I couldn't get even the most basic configuration running. After some experimenting and investigating, it turns out there's a problem with FirewallD. Here's what I did first on every single node. # firewall-cmd --permanent --add-service=docker-swarm # firewall-cmd --reload I launched a simple web service like this: # docker service create --name web -p 80:80 nginx My three nodes appear correctly with 'docker node ls'. >From here, I should be able to open the Nginx default web page in a web browser using any node's hostname. But nothing happens. No page is loaded. On a whim, I turned off FirewallD, and suddenly everything worked as expected. Now here's the list of ports that have to be open on every single node for Docker Swarm to work: * 2376/tcp * 2377/tcp * 7946/tcp * 7946/udp * 4789/udp And here's what docker-swarm.xml looks like under CentOS 7: # cat /usr/lib/firewalld/services/docker-swarm.xml <?xml version="1.0" encoding="utf-8"?> <service> <short>Docker integrated swarm mode</short> <description>Natively managed cluster of Docker Engines (>=1.12.0), where you deploy services.</description> <port port="2377" protocol="tcp"/> <port port="7946" protocol="tcp"/> <port port="7946" protocol="udp"/> <port port="4789" protocol="udp"/> <protocol value="esp"/> </service> So it looks like TCP port 2376 was forgotten in that service definition. I opened it up manually on every node: # firewall-cmd --permanent --add-port=2376/tcp # firewall-cmd --reload And now Docker Swarm works correctly. Cheers from the sunny South of France, Niki Kovacs -- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Site : https://www.microlinux.fr Blog : https://blog.microlinux.fr Mail : info at microlinux.fr Tél. : 04 66 63 10 32 Mob. : 06 51 80 12 12