add warning

Signed-off-by: Marc Schöchlin <[email protected]>

docs/guides/configuration-guide/services/kubernetes.md

@@ -7,6 +7,13 @@ sidebar_label: Kubernetes
 The deployment is based on [k3s-ansible](https://github.com/techno-tim/k3s-ansible) and the defaults
 are configured and described in [099-k3s.yml](https://github.com/osism/defaults/blob/main/all/099-k3s.yml)
 
+:::warning
+K3S is currently not installable on nodes that use a layer-3 underlay network by running an FRR
+instance on the node itself. The OSISM integration for this scenario is still pending.
+Metal-LB either uses ARP for the leader election (which cannot work in principle) or starts its own
+FRR instance which conflicts with the FRR instance of the host.
+:::
+
 1. Optional: If you run your environment begind a http proxy, [configure the proxy settings](../proxy.md)
 
 2. The use of more than 3 name servers for the Kubernetes nodes generates a large number of warning messages as only the first three name servers are used.
@@ -21,14 +28,13 @@ are configured and described in [099-k3s.yml](https://github.com/osism/defaults/
    openssl rand -base64 1024
    ```
 
-
 6. Add this token to the secrets file with the name `k3s_token`
 
    ```
    make ansible_vault_edit FILE=environments/secrets.yml EDITOR=<your favourite editor>
    ```
 
-   A example secret:
+   An example secret:
    ```
    k3s_token: |
       9nfWMSnntyozgwATpsxk/5UFRtW4sRfiDUIFH3JtqUr2vLJ+FN3qdUJyaLFMp0oa