public Builder setCidrBlock(java.lang.String value) {
        if (value == null) {
          throw new NullPointerException();
        }
        cidrBlock_ = value;
        bitField0_ |= 0x00000002;
        onChanged();
        return this;
      }
<pre>
Optional. cidr_block must be specified in CIDR notation when using
master_authorized_networks_config. Currently, the user could still use
the deprecated man_block field, so this field is currently optional, but
will be required in the future.
</pre>

<code>string cidr_block = 2 [(.google.api.field_behavior) = OPTIONAL];</code>

@param value The cidrBlock to set.
@return This builder for chaining.
java-telcoautomation/proto-google-cloud-telcoautomation-v1alpha1/src/main/java/com/google/cloud/telcoautomation/v1alpha1/MasterAuthorizedNetworksConfig.java