Explicitly mention the need for CASSANDRA_ENDPOINT_SNITCH when using DC/RACK variables

cassandra/content.md

@@ -122,11 +122,11 @@ This variable sets number of tokens for this node. It will set the [`num_tokens`
 
 ### `CASSANDRA_DC`
 
-This variable sets the datacenter name of this node. It will set the [`dc`](http://docs.datastax.com/en/cassandra/3.0/cassandra/architecture/archsnitchGossipPF.html) option of `cassandra-rackdc.properties`.
+This variable sets the datacenter name of this node. It will set the [`dc`](http://docs.datastax.com/en/cassandra/3.0/cassandra/architecture/archsnitchGossipPF.html) option of `cassandra-rackdc.properties`. You must set `CASSANDRA_ENDPOINT_SNITCH` to use the ["GossipingPropertyFileSnitch"](https://docs.datastax.com/en/cassandra/3.0/cassandra/architecture/archsnitchGossipPF.html) in order for Cassandra to apply `cassandra-rackdc.properties`, otherwise this variable will have no effect.
 
 ### `CASSANDRA_RACK`
 
-This variable sets the rack name of this node. It will set the [`rack`](http://docs.datastax.com/en/cassandra/3.0/cassandra/architecture/archsnitchGossipPF.html) option of `cassandra-rackdc.properties`.
+This variable sets the rack name of this node. It will set the [`rack`](http://docs.datastax.com/en/cassandra/3.0/cassandra/architecture/archsnitchGossipPF.html) option of `cassandra-rackdc.properties`. You must set `CASSANDRA_ENDPOINT_SNITCH` to use the ["GossipingPropertyFileSnitch"](https://docs.datastax.com/en/cassandra/3.0/cassandra/architecture/archsnitchGossipPF.html) in order for Cassandra to apply `cassandra-rackdc.properties`, otherwise this variable will have no effect.
 
 ### `CASSANDRA_ENDPOINT_SNITCH`