code: private Multimap<String, TokenRange> describeCassandraTopology(final Keyspace keyspace) {
          try {
              @SuppressWarnings ("unchecked")
              ConnectionPool<Cassandra.Client> connectionPool = (ConnectionPool<Cassandra.Client>) keyspace.getConnectionPool();
  
              return connectionPool.executeWithFailover(
                      new AbstractKeyspaceOperationImpl<Multimap<String, TokenRange>>(EmptyKeyspaceTracerFactory.getInstance().newTracer(CassandraOperationType.DESCRIBE_RING), keyspace.getKeyspaceName()) {
                          @Override
                          protected Multimap<String, TokenRange> internalExecute(Cassandra.Client client, ConnectionContext state)
                                  throws Exception {
                              Multimap<String, TokenRange> racks = ArrayListMultimap.create();
                              for (org.apache.cassandra.thrift.TokenRange tokenRange : client.describe_local_ring(getKeyspace())) {
                                  // The final local endpoint "owns" the token range, the rest are for replication
                                  EndpointDetails endpointDetails = Iterables.getLast(tokenRange.getEndpoint_details());
                                  racks.put(endpointDetails.getRack(),
                                          new TokenRangeImpl(tokenRange.getStart_token(), tokenRange.getEnd_token(), tokenRange.getEndpoints()));
                              }
                              return Multimaps.unmodifiableMultimap(racks);
                          }
                      },
                      keyspace.getConfig().getRetryPolicy().duplicate()).getResult();
          } catch (ConnectionException e) {
              throw Throwables.propagate(e);
          }
      }
docs: Gets the topology for a Cassandra keyspace as a Multimap, where the keys identify a rack (or availability zone
  in Amazon) and the values are the token ranges for each host in that rack.  For example, for a well distributed
  ring of 12 hosts and a replication factor of 3 this method would return a Multimap with 3 keys and each key would
  contain 4 token ranges.