I think I might be getting confused with terminology surrounding MTU.
This definition from Wendell Odom's CCNA book on MTU:
The IEEE 802.3 specification limits the data portion of the 802.3 frame to a minimum of 46 and a maximum of 1500 bytes. The term maximum transmission unit (MTU) defines the maximum layer 3 packet that can be sent over a medium. Because the layer 3 packet rests inside the data portion of an Ethernet frame, 1500 bytes is the largest IP MTU allowed over an Ethernet.
My understanding, is that an Ethernet frame is the last phase of encapsulation before it gets transmitted to the wire. When I look at a diagram of an Ethernet frame, its total size can equal a maximum of 1526 bytes.
Am I right in saying that an Ethernet frame MTU is 1526 while the MTU at the IP layer is 1500? Does the MTU change at each phase of encapsulation, or is the term "MTU" only meant to define the maximum size of a packet at layer 3?
Thanks for any help!