Fig 4. The seven different variants of the rNNI move.

Dashed edges indicate that there is no arc between those vertices. Gray arcs are those that change with the move. If vertices have additional incident arcs that are not drawn, then these may be oriented either way. These moves are only valid if the resulting network is acyclic. Note that the difference between (i) and (i*) is that (i*) reverses the direction of the uv arc.