[U-Boot] handling of bad blocks in nand

A short question to handling of bad blocks: My nand shows a few bad blocks (example 100000)

What is happen when I write / read from that block via nand write / read. Is content than ok (by mapping good blocks do that address)?

Other way around - if I have commands like

"get_kn=nand read.i 0x80000000 c0000 200000"

do I have to care for bad blocks in that range ? Di I have to make the part bigger to have some extra blocks, if one is skipped while write/read as it is bad?

Best regards Arno