Inter-switch VLAN communication: Which technologies allow VLAN traffic tagging across switches? Options: ISL, VTP, 802.1Q, 802.3z

Introduction / Context:
Switch-to-switch VLAN communication requires trunking protocols that encapsulate VLAN membership inside Ethernet frames. Cisco and IEEE standards differ.

Given Data / Assumptions:

• Protocols listed: ISL (Cisco), VTP, 802.1Q, 802.3z

Concept / Approach:
ISL and 802.1Q are VLAN trunking protocols. VTP is for VLAN database management, not tagging. 802.3z refers to Gigabit Ethernet physical standard, not VLAN tagging.

Step-by-Step Solution:

Verification / Alternative check:
Refer to Cisco docs: ISL and 802.1Q explicitly define VLAN tagging.

Why Other Options Are Wrong:

• VTP: Manages VLAN info, no frame encapsulation.
• 802.3z: Gigabit Ethernet, not trunking.

Common Pitfalls:
Confusing VTP’s VLAN management with inter-switch tagging; mixing physical layer with encapsulation protocols.

Final Answer:
1 and 3 (ISL and 802.1Q)