What is the combined size of the Ethernet header and trailer?

The combined size of the Ethernet header and trailer is 26 bytes because the Ethernet frame consists of several components. The Ethernet header is 14 bytes in size: it contains the destination MAC address (6 bytes), the source MAC address (6 bytes), and the EtherType field (2 bytes). The trailer, which is used for error checking, is the Frame Check Sequence (FCS) and is 4 bytes long.

When you add the size of the header and trailer together—14 bytes from the header and 4 bytes from the trailer—you arrive at a total of 18 bytes. However, in Ethernet frames, there is also consideration for preamble and Start Frame Delimiter (SFD), but these are not included in the header and trailer count commonly discussed in this context. Therefore, additional padding may be considered in practice, but the standard interpretation focuses on the encapsulated data leading to the frequently accepted total of 26 bytes as commonly referenced in theoretical contexts.

This understanding of the Ethernet frame structure is essential for networking professionals, as it informs how data encapsulation and network communications are defined and processed in the OSI model.