graph {
  rankdir=LR;
  node[shape=box,style=rounded,style=rounded,fillcolor=gray];


  subgraph cluster_sshportal {
      sshportal[penwidth=3.0,color=brown,fontcolor=brown,fontsize=20];
      shell[label="built-in\nadmin shell",color=orange,fontcolor=orange];
      db[color=gray,fontcolor=gray,shape=circle];
      { rank=same; db; sshportal; shell }
  }

  {
      node[color="green"];
      host1; host2; host3; hostN;
  }

  {
      node[color="blue"];
      user1; user2; user3; userN;
  }

  {
      edge[penwidth=3.0];
      user1 -- sshportal -- host1[color=red];
      user2 -- sshportal -- host2[color=blue];
      user3 -- sshportal -- host1[color=purple];
      user2 -- sshportal -- host3[color=green];
      user2 -- sshportal -- shell[color=orange,constraint=false];
  }

  userN -- sshportal[style=dotted];
  sshportal -- hostN[style=dotted];
  sshportal -- db[style=dotted,color=grey];

}