There are 2 options in campaign's settings screen-->detail - use internal DNC list and use campaign DNC list. Follow the ? sign next to them and read what each does.
Use Internal DNC List - This defines whether this campaign is to filter leads against the Internal DNC list. If it is set to Y, the hopper will look for each phone number in the DNC list before placing it in the hopper. If it is in the DNC list then it will change that lead status to DNCL so it cannot be dialed. Default is N.
Use Campaign DNC List - This defines whether this campaign is to filter leads against a DNC list that is specific to that campaign only. If it is set to Y, the hopper will look for each phone number in the campaign-specific DNC list before placing it in the hopper. If it is in the campaign-specific DNC list then it will change that lead status to DNCC so it cannot be dialed. Default is N.
As for what you needed- if campaign setting is made to use internal DNC list- those numbers would not be dialed no matter what campaign, however, this is not intended for large lists as would slow down putting leads in the hopper. In such case scrub lists in advance, before putting them into the database.
You can enter DNC numbers directly in the database, or use the relevant menu in ADMIN-->LISTS-->Add number to DNC, where you can also add a bunch of numbers at the same time (not quite sure what's the max at a time), depending on what version of vicidial you are using.