GraphViz for 3 routers

ThreeRouters.txt

digraph G {
    node[style=filled, fillcolor=red, landscape=True, width=2.5, height=1.25]

    R1 -> R2 [label="192.168.12.1/24", fontsize="12pt", arrowsize=0]
    R1 -> R3 [label="192.168.13.1/24", fontsize="12pt", arrowsize=0]
    R2 -> R3 [label="192.168.23.1/24", fontsize="12pt", arrowsize=0]
    R1 -> R1 [label="lo1: 10.1.1.1 ", fontsize="12pt"]
    R2 -> R2 [label="lo1: 10.2.2.2 ", fontsize="12pt"]
    R3 -> R3 [label="lo1: 10.3.3.3 ", fontsize="12pt"]

    {rank=same; R1; R2; R3}
    
    edge[constraint=false, dir=none]
    R1 -> R3 [style=invis]
    R2 -> R3 [style=invis]
}