Facilitating flexible maximum transmission unit packet core design in a communications network is provided herein. A system can comprise a processor and a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations. The operations can comprise receiving a first transmission unit setting from a first network device. The first transmission unit setting can indicate a size of a largest network layer protocol data unit that is able to be communicated in a single network transaction by the first network device. The operations can also comprise setting, at the device, a configuration of the first network device to the first transmission unit setting. Further, the operations can comprise sending first communication packets to the first network device using the first transmission unit setting and second communication packets to a second network device using a second transmission unit setting different from the first transmission unit setting.