ISL frames
The frame decoder recognizes an ISL-encapsulated frame if the frame being analyzed has a destination MAC address equal to 01:00:0C:00:00:0X or 03:00:0C:00:00:0X.
ISL length
The length of the ISL field is 26 bytes before the encapsulated Ethernet frame and 4 bytes of ISL CRC after the Ethernet frame.