Clarify topology aware hints needs explicit enabling

content/en/docs/concepts/services-networking/topology-aware-hints.md

@@ -19,6 +19,12 @@ those network endpoints can be routed closer to where it originated.
 For example, you can route traffic within a locality to reduce
 costs, or to improve network performance.
 
+{{< note >}}
+The "topology-aware hints" feature is at Beta stage and it is **NOT** enabled
+by default. To try out this feature, you have to enable the `TopologyAwareHints`
+[feature gate](/docs/reference/command-line-tools-reference/feature-gates/).
+{{< /note >}}
+
 <!-- body -->
 
 ## Motivation