Hello,
please see my answer in the thread below:
https://community.nxp.com/thread/510970
I am not sure, what kind of data you try send from PC to MPC5748G, but if you check function RX handler, there is switch which tells you, which handler should be used for receiving data. But as soon as the value in Ethernet frame length field does not meet any of the value used in this function (0x8100 for VLAN, 0x0800 for IPv4, 0x0806 for ARP or 0x86DD for IPv6), microcontroller does not receive packet sent from PC.
This is the limitation I described in the thread mentioned above. This is the reason why this example is not good for more complex TCP/IP communication and it is better to use LwIP stack.
Regards,
Martin