Deck ledger board on extended deck

I have a small 6 X 9 ft deck planned where four solid corner posts are set in a 6 ft square. So I will have 3 feet extended beyond the end of the posts. I will have ledger boards around the perimeter with 9 ft joists. I will also have a support board attached to the far posts under the joists keeping them from falling. So I’ll have a 3 ft ledge and don’t know how to attach the ledger board at the end. THe joists will attach to this ledger board to keep them in place, but I don’t know how to keep gravity from taking down the ledger board. It will be attached to the two side ledger boards…is that enough to support that entire end? I can’t support that far ledger board to the ground or to another post, it will truly be out hanging in space.
I was thinking of running another board flat along the joists above or below the joists (or both), and attaching this board to the joists and the ledger board.

Hopefully, I’ve explained the problem well enough, I seek advice to keep that far ledger board from falling off

The boards you’re talking about are the rim joists, not ledger boards. Ledger boards attach a deck to a building or other fixed structure. You’re building a freestanding deck. By definition, a freestanding deck doesn’t have a ledger board.

You should read the DCA 6 Prescriptive Residential Wood Deck Construction Guide. It will tell you what size footings, posts, beams, and joists you must use to build a safe, code-compliant deck. This is especially important when building a cantilevered deck, as you are doing. There are illustrations of how decks are constructed.

Here are some important things that you might not know:

It’s not acceptable to attach a beam or joist to the side of a post. People do this all the time but it’s wrong and makes the deck more likely to fail.

There’s a lot of hardware involved. Posts should sit on metal post bases to provide proper attachment to concrete footings. Joists have to be attached using joist hangers, not end-nailed through the rim joist. Joists must be attached to beams with appropriate hardware (hurricane ties, generally). Generally, anywhere that two boards meet will have have hardware to strengthen the connection.

Proper bracing is crucial in a freestanding deck. People often get this detail wrong. Incorrect bracing can lead to a deck simply falling over when horizontal forces are applied.

Most municipalities have code requirements for any deck more than 30" off the ground, and require a permit to be pulled. Part of the process is to submit design drawings for approval. Your city/county should have online guidance for deck design.

I reread the OP. You’re planning a 3-foot cantilever on a 9-foot joist. That’s too far. The DCA6 will tell you how far you can cantilever for a given joist length and size. There’s no joist size which can acceptably cantilever 33% of the joist’s length. If you build this it will collapse when too many people stand on that end of the deck.

THanks all
I think I’ll do something else then.

Do you even have a name for the project? Something like Moby Deck, or Biggus Deckus?