graph G { fontname="Helvetica,Arial,sans-serif" node [fontname="Helvetica,Arial,sans-serif"] edge [fontname="Helvetica,Arial,sans-serif"] layout=fdp e subgraph clusterA { a -- b; subgraph clusterC { C -- D; } } subgraph clusterB { d -- f } d -- D e -- clusterB clusterC -- clusterB }