speed bump 20mph-bang underneath-rattling sound when starts car & at stop lite

Firestone checked heat shields, not loose but long pipe going out back of car (exhaust?) is loose near the back & banging on something under it. They did not suggest a fix. No bracket to hold it up in place. Suggestions? If not fixed & left alone, will it be a problem?

It should not be a problem but, if you want the noise to go away (depending on the location of the banging where it is loose), I would either suggest an exhaust clamp with a slip-sleeve or perhaps a weld to fix the loose connection.