graph abc {
  subgraph clusterX {
    style="dashed,rounded" color=purple
  }
  subgraph clusterY {
    margin=22
    style="dotted,bold" color=green
  }
}
//////////////////////////////////////////////
graph G {  
  ranksep=.4
  edge[style=invis]
  subgraph "cluster1" {
    margin=38
    labelloc=b
    label="192.168.135.101";
    master    server1 server2
    master -- server1 -- server2;
  }
  label="my graph"
}
