FRITZ!Box 7490 Service - Knowledge Base
Oversized packet support (jumbo frames)
All data is grouped into individual packets (Ethernet frames) for the communication between the devices in the FRITZ!Box home network. The Maximum Transmission Unit (MTU) describes the maximum size of the protocol data that can transferred in a single data packet; it is defined in the IEEE 802.3 Ethernet standard and and is 1518 bytes. The FRITZ!Box transmits all packets that comply with the IEEE 802.3 Ethernet standard.
Currently the FRITZ!Box does not support Ethernet packets containing more than 1518 bytes (jumbo frames).