The FRITZ!Box does not offer the possibility to adjust the MTU size manually. This is also not necessary because the FRITZ!Box supports MSS clamping (Maximum Segment Size) that automatically adjusts the size of the data packets to the smaller MTU of the interconnected networks. This means that there will be no performance degradation due to the fragmenting or discarding of data packets.

Note:The Maximum Transmission Unit (MTU) indicates the maximum size of user data that can be transmitted in a single data packet. The maximum MTU is 1492 bytes for DSL connections established via PPPoE (Point to Point Protocol over Ethernet). The maximum MTU is 1500 bytes for cable and fiber optic connections. The internet service provider can reduce the MTU by using additional protocols.