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Network+ Exam

VLAN Configuration

October 29, 2025

  • #network+

VLAN Configuration

802.1Q Tagging - VLAN tagging refers to the standard that allows the frame to have a ethernet tag inserted into it to help the switch to ID. creates the logical separation on the VLANs.

Trunking the transmission of traffic from different VLANs on the same cable, but keeping it separate. used

Native VLAN the one VLAN on a trunk port that does not get a vlan tag. need to rename the native vlan.

Voice VLAN - dedicated toi voice or VOIP. voice traffic is hightly sensive to packet loss. You can prioritize it above other traffice to reduce latency , jitter and packet loss.

Link Aggregation - port channeling or bonding as a wey to combine mulitple ntwork connections into one link. commonly used to support trunking lines between the switches. by aggriagion 4 ine gigabit lines you get a 4gigabit connection, and creates redundancy.

Speed and Duplex Configurations. - the settings that tdetermine the rate at which commincation will happen and the mode of communicatipon.

Auto negotion may pick this for you. if you have legacy systems, then you may want to use auto configs.

VLAN & Switching Features (N10-009)

802.1Q VLAN Tagging

  • Standard for VLAN tagging on Ethernet frames.
  • Inserts a 4-byte VLAN ID tag into the frame header.
  • Allows switches to identify which VLAN the traffic belongs to.
  • Provides logical separation of VLANs across shared infrastructure.

Trunking

  • A single physical link can carry multiple VLANs using 802.1Q tagging.
  • Common between switch-to-switch or switch-to-router connections.
  • Keeps VLAN traffic separate while sharing the same cable.

Native VLAN

  • VLAN on a trunk port that is not tagged.
  • By default = VLAN 1.
  • Best Practice: Rename/change it (security hardening).

Voice VLAN

  • Special VLAN for VoIP traffic.
  • Voice is highly sensitive to latency, jitter, and packet loss.
  • Traffic can be prioritized (QoS) over data VLAN traffic.
  • Ensures clear, low-delay calls.

Link Aggregation

  • Also called Port Channeling / Bonding / LACP (802.3ad).
  • Combines multiple physical links into a single logical connection.
  • Benefits:
    • Increased bandwidth (e.g., 4 × 1 Gb = 4 Gb).
    • Redundancy (if one link fails, traffic continues).
  • Commonly used for trunk links between switches.

Speed & Duplex Configurations

  • Speed: Transmission rate (e.g., 100 Mbps, 1 Gbps, 10 Gbps).
  • Duplex:
    • Half-duplex: Send OR receive at one time (old hubs).
    • Full-duplex: Send AND receive simultaneously (modern switches).
  • Auto-Negotiation:
    • Devices detect best speed/duplex automatically.
    • Legacy systems may require manual config to prevent mismatches.
    • Duplex mismatch = common cause of slow or erratic network performance.

✅ Must-Know Exam Points

  • 802.1Q = VLAN tagging standard.
  • Trunk link = multiple VLANs over one cable.
  • Native VLAN = untagged VLAN; default is VLAN 1, should be changed.
  • Voice VLAN = prioritizes VoIP traffic.
  • Link Aggregation (LACP) = bandwidth + redundancy.
  • Full-duplex on switches eliminates collisions.

⚡ Flashcard Drill

  • Q: What VLAN is untagged on a trunk port?

    A: Native VLAN.

  • Q: Which standard defines link aggregation?

    A: IEEE 802.3ad (LACP).

  • Q: What does 802.1Q provide?

    A: VLAN tagging.

  • Q: What’s a common cause of slow speeds due to misconfiguration?

    A: Duplex mismatch.