The IP packet you are talking about may not be an IP datagram, Ethernet frames encapsulate IP datagrams, in Ethernet, the maximum transmission unit MTU is 1500 bytes, in an IP packet, removing the 20 bytes of the IP packet header, the maximum length of data that can be transmitted is 1480 bytes. In a TCP packet, the maximum data segment that can be transmitted by removing the 20 TCP packet headers is 1460 bytes. Therefore, when the data exceeds the maximum data length, the data will be sliced, and you will see multiple slices being transmitted in the IP packet header, but the identification number is the same, indicating that it is the same packet.

The maximum length of an IP packet is 2 to the 16th power minus 1, i.e.: 65535 bytes. Therefore, the maximum IP packet that can be transmitted in Ethernet is 65535 bytes.