Which three pairs of trunking modes will establish a functional trunk link between two Cisco switches? (Choose three.)

To establish a functional trunk link between two Cisco switches, the ports on both ends must be compatible and correctly negotiate the trunking status. Here are the modes that can successfully form a trunk:

1. Dynamic Desirable – Dynamic Desirable: Both sides actively attempt to negotiate a trunk link using DTP (Dynamic Trunking Protocol).
2. Dynamic Desirable – Dynamic Auto: One side actively attempts to negotiate a trunk link, and the other side is willing to convert to a trunk link if the other side initiates negotiation.
3. Dynamic Desirable – Trunk: One side actively attempts to negotiate, while the other side is set to trunk mode and will form a trunk link.

The other combinations you’ve mentioned would not result in a trunk being formed:

• Access – Trunk: This pairing does not form a trunk because one side is set to never trunk (access).
• Dynamic Auto – Dynamic Auto: Neither side actively attempts to initiate trunking, so they will not form a trunk unless the other side initiates it.
• Access – Dynamic Auto: The access mode side is set to never trunk, and the dynamic auto side will not initiate a trunk, so a trunk will not form.

Therefore, the three pairs that will establish a functional trunk link are:

• Dynamic Desirable – Dynamic Desirable
• Dynamic Desirable – Dynamic Auto
• Dynamic Desirable – Trunk