title: Istio allow only specific IP CIDR and deny rest
body: <p>I have a requirement where-in I would like to allow certain CIDR ranges to be able to access my service, rest all should be denied.</p>
  
  <p>I have tried the Istio IP Whitelisting/Blacklisting as mentioned in the official Istio documentation. </p>
  
  <p>For example 10.0.0.2/16 should get allowed and rest should be denied. This doesn't seem to work.</p>
  
  <pre><code>apiVersion: config.istio.io/v1alpha2
  kind: handler
  metadata:
    name: whitelistip
  spec:
    compiledAdapter: listchecker
    params:
      # providerUrl: ordinarily black and white lists are maintained
      # externally and fetched asynchronously using the providerUrl.
      overrides: ["10.0.0.2/16"]  # overrides provide a static list
      blacklist: true 
      entryType: IP_ADDRESSES
  ---
  apiVersion: config.istio.io/v1alpha2
  kind: instance
  metadata:
    name: sourceip
  spec:
  </code></pre>