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Cisco CCNA 2.1 Cisco CCNA 4.7
TechKnowSurge Catalog Interactives Voice VLAN or Data VLAN?
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Voice VLAN or Data VLAN?

An IP phone with a laptop behind it on one port: whose traffic lands in which VLAN?

⚑ Complete this interactive to capture a CTF flag worth 5 points.

About this interactive

From the lesson: - **Voice gets its own VLAN** so call traffic, which suffers above about 150 ms of delay, can be prioritized. - **The phone is a small switch.** One port goes to the wall jack, the other to the PC, so a desk needs one switch port. - **One access port, two VLANs.** The port is an access port in the data VLAN, plus a voice VLAN. The phone learns the voice VLAN from the switch through CDP and tags its own frames with it; the PC's frames pass through untagged and land in the data VLAN. - **Marking:** at Layer 2 the priority is the class of service (CoS), 3 bits in the 802.1Q tag. At Layer 3 it is the DSCP value in the IP header. (The video says "cost of service"; it is class of service.)

What you'll learn

Aligned to

Cisco CCNA
2.1 Configure and verify VLANs (normal range) spanning multiple switches
4.7 Explain the forwarding per-hop behavior (PHB) for QoS

Key terms

Voice VLAN
A VLAN dedicated to IP telephony traffic, configured on an access port alongside a data VLAN. The switch instructs the attached IP phone via CDP or LLDP-MED to tag its voice frames with the voice VLAN ID, while an attached PC's untagged frames remain in the data VLAN.
Access Port
A switch port that belongs to a single data VLAN and sends and receives untagged frames, used for connecting end devices such as PCs and printers. An access port may additionally carry a tagged voice VLAN for an IP phone without becoming a trunk.
Class of Service
CoS
A Layer 2 QoS mechanism that uses the 3-bit Priority Code Point field in an IEEE 802.1Q VLAN tag to classify and prioritize network traffic into up to eight service classes. CoS markings are used by switches to apply differential queuing and forwarding treatment.
Quality of Service
QoS
A set of techniques used to manage network traffic by classifying, marking, and prioritizing certain data types to ensure consistent performance for latency-sensitive applications such as voice and video. QoS mechanisms include traffic shaping, queuing, and policing applied at each network device.
Voice over IP
VoIP
Technology that digitizes analog voice signals and transmits them as IP packets over a network, enabling telephone calls over data networks instead of traditional circuit-switched telephone infrastructure. VoIP requires careful QoS configuration to minimize latency, jitter, and packet loss that degrade call quality.
802.1Q Tag
An optional four-octet field inserted into an Ethernet frame header to identify which VLAN the frame belongs to.

Topics

Voice Vlan Data Vlan Ip Phones Qos Class Of Service Interactive Streak Sort

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