Creation known issues topic (#28)

content/docs/known-issues.md

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+# Known issues
+
+Workaround solutions are available for the following MKE 4.0.0-alpha.1.0 known
+issues:
+
+## [BOP-708] OIDC authenticaion fails after mkectl upgrade
+
+Due to an issue with client secret migration, OIDC authentication fails
+following an upgrade performed with mkectl.
+
+**Workaround:**
+
+1. Copy the MKE 4 config that prints at the end of migration.
+
+2. Update the ``authentication.oidc.clientSecret`` field to the secret field
+   from your identity provider.
+
+3. Apply the updated MKE 4 config.
+
+## [BOP-686] In MKE 3 upgrade, kubectl commands return ``No agent available``
+
+For a cluster with multiple controller nodes (manager/master nodes), [k0s
+requires the presence ofa load balancer for the controller
+node](https://docs.k0sproject.io/head/high-availability/ ). Without a load
+balancer, the controller nodes is unable to reach the kubelet on the worker
+nodes, and thus the user will be presented with ``No agent available`` errors.
+
+**Workaround:**
+
+1. If an external load balancer is not already in place, create one that
+   targets all controllers and that forwards the following ports:
+
+   - `443`, for controller
+   - `6443`, for Kubernetes API
+   - `8132`, for Konnectivity
+
+2. Use `k0sctl` to update the `k0s` config to set `externalAddress`:
+
+   ```
+   k0s:
+     config:
+       spec:
+         api:
+           externalAddress: <load balancer public ip address>
+           sans:
+           - <load balancer public ip address>
+   ```