Most designers output a drill file instead of a Gerber file for the vias. If the drill goes all the way through the board, then there is only one such file.

In order to use the drill data, you first bring it into the DRILL2GBR utility, convert it to a Gerber file (with same format and units as the other Gerber files). When running NETEX-G you select this file (or files) in the Drill dialog and indicate what layers the drill passes through.

On each conductor layer that the drill passes through a round piece of metal is generated that is the same diameter as the drill. If metal on that layer connects to the hole location (for example a pad or a solid ground plane) then a connection to that layer is made. If no metal touches the newly created round then no connection is made - however the round metal produced by the drill remains.