Editing IP Controller

In order for kubernetes services to be accessible outside the cluster, they need to have externally routable IP addresses.  While it would seem that this is a basic need that should be provided by kubernetes itself, its implementation is actually very dependent on the underlying platform -- and therefore left for the provider to implement.

We are using the bare metal load balancer called [https://metallb.universe.tf/ MetalLB].  It is a full featured loadbalancer and IP controller that has multiple modes of operation.  As deployed here, it is using simple Layer 2 operation, advertising IP addresses using the existing network interfaces.

The basic load balancer is deployed with a simple manifest:

 <nowiki>kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.14.3/config/manifests/metallb-native.yaml
</nowiki>

At this point, the controller itself is active, but it has nothing to do -- it doesn't have any IP addresses to hand out.  The controller uses a Custom Resource Definition to define address pools, allocation methods, and routing protocols.  There are multiple definitions in the [https://gitlab.williams-net.org/k8s/k8s-admin k8s-admin repository on GitLab], use the one appropriate to the system:

{| class="wikitable"
|-
! filename !! IP range
|-
| ipaddresspool-prod.yaml || 10.0.0.110 - 10.0.0.127
|}

Apply the correct pool definition to get things working:
 kubectl apply -f <filename>

This loadbalancer implementation supports the requesting of IP addresses through the '''loadBalancerIP''' parameter in the service -- if the address is available, it will allocate it.  The '''externalTrafficPolicy''' parameter is also respected.

See the home page for the MetalLB package for complete installation and configuration options.

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