How does commission splits usually work between the Salesperson, and employing broker?

For example, as the Salesperson #1) If you get the listing, and you sell the property - how much of the 6% do you usually have to share with your employing broker? #2) If you get the listing, and another agent sells the property. Or you sell the property, and another agent gets the listing - how much of the 3% do you usually have to share with your employing broker? #3) If your employing broker gets the listing, and you sell the listing - is this basically the same relationship as #2? You're employing broker would be the "Listing Agent", and you are the "Sales Agent", except you have to share a portion of your 3% as well? Thanks.