baby giant
jargonnetworking
A frame just slightly over the classic 1518-byte Ethernet maximum - grown by tags and labels, not by payload.
One 802.1Q VLAN tag makes 1522, QinQ makes 1526, a couple of MPLS labels push further. The payload is still a normal 1500 bytes; only the header grew. Switch platforms accept them by carrying frame headroom, which is why system MTUs read 9216 while the IP MTU stays put.
A baby giant is a frame slightly larger than the classic 1518-byte Ethernet maximum, typically because VLAN tags or MPLS labels added a few bytes to an otherwise standard frame. It is not a jumbo frame and it needs different handling.
The failure is quiet and specific. A switch that has not been configured to accept the extra bytes drops these frames while passing everything else, so a trunk carrying tagged traffic loses full-size packets and passes small ones. The symptom is the familiar small-works-large-fails pattern, and the fix is a system MTU adjustment rather than jumbo frame configuration, which is why knowing the distinction saves a diagnostic detour.
Also known as: baby giants, baby giant frames