I can’t find anywhere in Cilium docs how to achieve this:
Can you please point me to the correct document?
It is here.
Although the manifest example is for ingressDeny on a CiliumClusterwideNetworkPolicy , you can substitute CiliumNetworkPolicy and egressDeny here and the properties are pretty much the same excpet fieldnames starting with from for ingress start with to for egress.
Also
kubectl explain ciliumnetworkpolicy.spec.egressDeny
At CKS level, you should be comfortable with using kubectl explain