enable listen_interface for cassandra

Change-Id: I11b6613534d39ac4809812028e48d20dd4bbc9d8
diff --git a/README.rst b/README.rst
index 307ae1c..c0b397e 100644
--- a/README.rst
+++ b/README.rst
@@ -623,6 +623,18 @@
         multi_tenancy: false
       ...
 
+Cassandra listen interface
+------------------------------
+
+.. code-block:: yaml
+  
+    database:
+      ....
+      bind:
+        interface: eth0
+        port: 9042
+        rpc_port: 9160
+      ....
 
 Usage
 =====