Overview
tcpreplay has evolved quite a bit over the years. In the 1.x days, it merely read packets and sent then back on the wire. In 2.x, tcpreplay was enhanced significantly to add various rewriting functionality but at the cost of complexity, performance and bloat. In 3.x, tcpreplay has returned to its roots to be a lean packet sending machine and the editing functions have moved to tcprewrite and a powerful tcpreplay-edit which combines the two. In 4.0 some editing capabilities where added back into tcpreplay but only in the case where performance was not affected (`–unique-ip).
Since tcpreplay-edit includes all the functionality of both *tcpreplay and tcprewrite, please see those wiki pages for how to use tcpreplay-edit.
Lastly, please remember that the packet editing code has some overhead- even when not in use. Hence, for the highest performance I always recommend using tcprewrite and tcpreplay separately.