Hi everyone,

I understand what happens when Segwit nodes broadcasts new transactions to non-Segwit (or legacy) nodes. Putting in a simple way, transactions are transmitted without witness data and is still considered valid to the legacy. Then, legacy validates it, adds to the mempool and broadcasts to all connected nodes.

What I don't understand is the opposite way. What happens when a legacy (or non-Segwit) node sends transactions to Segwit nodes? Segwit nodes understand this "old fashion" transaction? Or it needs to transform it into a Segwit transaction by "rearranging" the witness data before validating it and adding to the mempool?

The same questioning goes to the block when a non-Segwit node broadcasts it to a Segwit node.

Thanks in advance