Cloud Compatibility

In general, MetalLB is not compatible with cloud providers.

MetalLB is for bare-metal clusters, and even cloud providers that offer “dedicated servers” usually don’t support the network protocols that MetalLB requires.

This is an incomplete list of cloud providers and platforms. If your platform isn’t listed here, its support status is unknown, but it’s very likely that the answer is “no”. If you know for sure, please send a pull request to update this list!

Why doesn’t MetalLB work on (most) cloud platforms?

MetalLB implements load balancers using standard routing protocols. However, in general, cloud platforms don’t implement those routing protocols in a way that MetalLB can leverage.

In particular:

• BGP support is uncommon, and is usually designed to support inbound route advertisement from off-cloud locations (e.g. Google Cloud Router). MetalLB’s BGP mode therefore either doesn’t work at all, or doesn’t do what most people want - and definitely does it worse than the cloud platform’s own load-balancer products.
• ARP is emulated by the virtual network layer, meaning that only IPs assigned to VMs by the cloud platform can be resolved. This breaks MetalLB’s L2 mode, which relies on ARP’s behavior on normal Ethernet networks.
• Even in cases where ARP works normally, the IP allocation process for public IPs (often called “floating IPs”) doesn’t integrate with the virtual network in a standard way, so MetalLB can’t “grab” the IP with ARP and route it to the correct place. Instead, you have to talk to the cloud’s proprietary API to reroute the floating IP, which MetalLB can’t do.

The short version is: cloud providers expose proprietary APIs instead of standard protocols to control their network layer, and MetalLB doesn’t work with those APIs.

Platform-Specific Notes

MetalLB on OpenShift OCP

To run MetalLB on OpenShift, two changes are required: changing the pod UIDs, and granting MetalLB additional networking privileges.

Pods get UIDs automatically assigned based on an OpenShift-managed UID range, so you have to remove the hardcoded unprivileged UID from the MetalLB manifests. You can do this by removing the spec.template.spec.securityContext.runAsUser field from both the controller Deployment and the speaker DaemonSet. Also, as the allowed group ID range in Openshift is 5000 through 5999, you have to remove spec.template.spec.securityContext.fsGroup field as well.

Additionally, you have to grant the speaker DaemonSet elevated privileges, so that it can do the raw networking required to make load balancers work. You can do this with:

oc adm policy add-scc-to-user privileged -n metallb-system -z speaker

After that, MetalLB should work normally.

MetalLB on OpenStack

You can run a Kubernetes cluster on OpenStack VMs, and use MetalLB as the load balancer. However you have to disable OpenStack’s ARP spoofing protection if you want to use L2 mode. You must disable it on all the VMs that are running Kubernetes.

By design, MetalLB’s L2 mode looks like an ARP spoofing attempt to OpenStack, because we’re announcing IP addresses that OpenStack doesn’t know about. There’s currently no way to make OpenStack cooperate with MetalLB here, so we have to turn off the spoofing protection entirely.

MetalLB on Equinix Metal

Equinix Metal is an unusually “bare metal” cloud platform, and supports using BGP to advertise and route floating IPs to machines. As such, MetalLB’s BGP mode works great on Equinix Metal! There is even a tutorial written by the folks at Equinix Metal, that use MetalLB to integrate Kubernetes load balancers with their BGP infrastructure.

Alternatives

If MetalLB doesn’t work with your cloud platform, you have two main alternatives.

Use the platform’s load balancer

If your cloud platform has a load-balancer product, you should use that. It’s probably going to be more featureful and higher performance than MetalLB anyway, and probably has a Kubernetes integration that’s maintained by the cloud provider.

Use keepalived-vip

keepalived-vip is a simple wrapper around keepalived, which some people have successfully used to configure virtual IPs with Kubernetes. The key feature that makes this work is that keepalived supports shell script hooks when a failover event occurs, so you can write a custom shell script that talks to your cloud platform’s APIs and do the right thing.

Note that keepalived-vip by itself still won’t work properly. Keepalived implements VRRP, which is roughly equivalent to MetalLB’s L2 mode. If MetalLB’s L2 mode doesn’t work, Keepalived’s VRRP won’t either… but with the hook shell scripts, you can write the glue code for the cloud API.

The resulting system is less well integrated with Kubernetes (LoadBalancer Service objects still won’t work), and mostly only makes sense coupled with an HTTP(S) ingress controller. It’s also not very widely used, so documentation isn’t great. That said, a search for “ keepalived-vip” should hopefully get you some useful information to implement this method.

Can MetalLB support my cloud provider?

In theory, it would be possible for MetalLB to support cloud provider APIs and provide the same functionality as with standard network protocols on bare metal.

This is currently out of scope for MetalLB, for one primary reason: MetalLB has no funding to pay for the cloud resources to test these integrations. If the cloud providers, or some other sponsor, is willing to pay for the resources (servers, IPs, …) required to test the integration, then we could potentially add support to MetalLB.

If you think you can help with getting resources for testing, file a bug and we can talk about it!