Cisco Certified Support Technician (CCST) NetworkingNetwork AccessHard
A network technician is configuring a new Cisco switch. To ensure that multiple VLANs can traverse a single physical link between this switch and another switch, the technician must configure the port as a trunk port. Which encapsulation protocol is typically used on Cisco switches for VLAN trunking?
- APPP
- BHDLC
- C802.1Q
- DARP
Show answer & explanationAnswer & explanation
Correct answer: C. 802.1Q
IEEE 802.1Q is the industry-standard protocol for VLAN tagging on Ethernet trunk links. It inserts a 4-byte tag into the Ethernet frame header to identify the VLAN to which the frame belongs, allowing multiple VLANs to share a single physical link.
Why the other options are wrong
- A. PPP (Point-to-Point Protocol) is a WAN encapsulation protocol used for direct serial connections, not for VLAN trunking.
- B. HDLC (High-Level Data Link Control) is a WAN encapsulation protocol, not used for VLAN trunking on Ethernet switches.
- D. ARP (Address Resolution Protocol) resolves IP addresses to MAC addresses within a local network, unrelated to VLAN trunking encapsulation.
IEEE 802.1Q
The industry-standard protocol for VLAN tagging on Ethernet frames, which allows multiple Virtual Local Area Networks (VLANs) to share a single physical network link (trunk port).
- Inserts a 4-byte tag into Ethernet frames
- Identifies the VLAN ID (VID)
- Enables trunking for multiple VLANs
- Replaced Cisco's proprietary ISL in most modern networks
Memory trick: 802.1Q puts the VLAN tag on the trunk.