ISL is being configured on a Company switch. Which of the following choices are true regarding the ISL protocol? (Choose two)

A.
It can be used between Cisco and non-Cisco switch devices.

B.
It calculates a new CRC field on top of the existing CRC field.

C.
It adds 4 bytes of protocol-specific information to the original Ethernet frame.

D.
It adds 30 bytes of protocol-specific information to the original Ethernet frame.

Explanation:

ISL adds a total of 30bytes to the Ethernet frame. A 26 byte header (10bytes identifies the VLAN ID) and a 4 byte trailer (containing a separate CRC).
Incorrect Answers:
A: This is incorrect because ISL is Cisco proprietary and can only be used on Cisco devices. For configuring a trunk to a non-Cisco switch, 802.1Q encapsulation should be used.
C: This is incorrect because it is contradictory to D. 30 byes are added with ISL, not 4 bytes. This choice describes what is used in 802.1Q frames, not ISL