Skip to content


While having a self-healing, scalable docker swarm is great for availability and scalability, none of that is worth a sausage if nobody can connect to your cluster!

In order to provide seamless external access to clustered resources, regardless of which node they're on and tolerant of node failure, you need to present a single IP to the world for external access.

Normally this is done using a HA loadbalancer, but since Docker Swarm aready provides the load-balancing capabilities (routing mesh), all we need for seamless HA is a virtual IP which will be provided by more than one docker node.

This is accomplished with the use of keepalived on at least two nodes.

Ceph Screenshot



Already deployed:

  • At least 2 x swarm nodes
  • low-latency link (i.e., no WAN links)


  • At least 3 x IPv4 addresses (*one for each node and one for the virtual IP1)


Enable IPVS module

On all nodes which will participate in keepalived, we need the "ip_vs" kernel module, in order to permit services to bind to non-local interface addresses.

Set this up once-off for both the primary and secondary nodes, by running:

echo "modprobe ip_vs" >> /etc/modules
modprobe ip_vs

Setup nodes

Assuming your IPs are as per the following example:

  • : Primary
  • : Secondary
  • : Virtual

Run the following on the primary

docker run -d --name keepalived --restart=always \
  --cap-add=NET_ADMIN --cap-add=NET_BROADCAST --cap-add=NET_RAW --net=host \

And on the secondary2:

docker run -d --name keepalived --restart=always \
  --cap-add=NET_ADMIN --cap-add=NET_BROADCAST --cap-add=NET_RAW --net=host \


That's it. Each node will talk to the other via unicast (no need to un-firewall multicast addresses), and the node with the highest priority gets to be the master. When ingress traffic arrives on the master node via the VIP, docker's routing mesh will deliver it to the appropriate docker node.


What have we achieved?



  • A Virtual IP to which all cluster traffic can be forwarded externally, making it "Highly Available"

The easy, 5-minute install

I share (with sponsors and patrons) a private "premix" GitHub repository, which includes an ansible playbook for deploying the entire Geek's Cookbook stack, automatically. This means that members can create the entire environment with just a git pull and an ansible-playbook deploy.yml 👍

Chef's notes 📓

  1. Some hosting platforms (OpenStack, for one) won't allow you to simply "claim" a virtual IP. Each node is only able to receive traffic targetted to its unique IP, unless certain security controls are disabled by the cloud administrator. In this case, keepalived is not the right solution, and a platform-specific load-balancing solution should be used. In OpenStack, this is Neutron's "Load Balancer As A Service" (LBAAS) component. AWS, GCP and Azure would likely include similar protections. 

  2. More than 2 nodes can participate in keepalived. Simply ensure that each node has the appropriate priority set, and the node with the highest priority will become the master. 

Tip your waiter (sponsor) 👏

Did you receive excellent service? Want to compliment the chef? (..and support development of current and future recipes!) Sponsor me on Github / Ko-Fi / Patreon, or see the contribute page for more (free or paid) ways to say thank you! 👏

Employ your chef (engage) 🤝

Is this too much of a geeky PITA? Do you just want results, stat? I do this for a living - I'm a full-time Kubernetes contractor, providing consulting and engineering expertise to businesses needing short-term, short-notice support in the cloud-native space, including AWS/Azure/GKE, Kubernetes, CI/CD and automation.

Learn more about working with me here.

Flirt with waiter (subscribe) 💌

Want to know now when this recipe gets updated, or when future recipes are added? Subscribe to the RSS feed, or leave your email address below, and we'll keep you updated.

Your comments? 💬