CCNA Practice Exam 2025 – Complete Study Resource

The default Maximum Transmission Unit (MTU) size for Ethernet frames is 1500 bytes. This value is significant because it represents the largest size of a single data packet that can be sent over an Ethernet network without needing to be fragmented. When an Ethernet frame is larger than the MTU, it will be split into smaller packets, which can lead to increased overhead and reduced performance due to the additional processing required for reassembling these packets at the destination.

Having a standard MTU size of 1500 bytes allows for efficient utilization of network resources and is widely supported across various networking devices and protocols. This standardization aids in ensuring compatibility and optimal performance within network communications. The other options, such as 1492, 1400, and 1600, can be associated with specific scenarios or technologies, but they are not the default MTU size for standard Ethernet frames. For instance, 1492 may be relevant to PPPoE connections, which reduces the MTU slightly to accommodate the overhead of the PPPoE header.