I've been using EDraw. You can select the rack shape, then click the float button to modify the rack numbers. To change the thinkness of the links between the devices, you can set it as line outline. Select the line, then set the line width.
..or this with either of LibreOffice or OpenOffice draw:
The Draw app in Libre/OpenOffice support the use of styles with lines, so you can define "fibre", "CAT6", "trunk" etc styles and then easily adjust colour, thickness for all lines in your diagram just by updating the styles.