About this interactive
From the lesson:
- **The native VLAN is the one VLAN a trunk carries untagged.** Every other VLAN on that trunk is tagged.
- **It is a per-link setting,** made on the interface. Each trunk can have a different native VLAN, but both ends of one trunk must agree. Cisco's CDP reports a native VLAN mismatch.
- **Cisco's default native VLAN is 1,** so a trunk left at defaults sends VLAN 1 untagged.
- **Why it exists:** legacy devices and some Layer 2 protocols send untagged frames.
- **Good practice:** use the same native VLAN on every trunk, and pick one no hosts use, for a little extra security.
What you'll learn
- Decide whether a frame crosses a trunk tagged or untagged: only the trunk's native VLAN is untagged
- Apply the native VLAN as a per-link setting with a Cisco default of VLAN 1, which must match at both ends
Aligned to
Cisco CCNA
2.2
Configure and verify interswitch connectivity
Key terms
- Native VLAN
- The one VLAN on an 802.1Q trunk whose frames are sent untagged. Any untagged frame received on the trunk is assigned to it. Both ends of a trunk must be configured with the same native VLAN.
- 802.1Q Tag
- An optional four-octet field inserted into an Ethernet frame header to identify which VLAN the frame belongs to.
- VLAN Trunk
- A point-to-point link between two switches that carries traffic for multiple VLANs simultaneously using IEEE 802.1Q tagging.
- Native VLAN Mismatch
- A misconfiguration where the two endpoints of a trunk link are configured with different native VLANs, which can cause traffic to be forwarded to the wrong VLAN.
- Default VLAN
- The pre-configured VLAN on a switch that all ports belong to out of the box, allowing immediate operation before any custom VLAN programming; on Cisco switches this is VLAN 1, which cannot be deleted or renamed.
Topics
Native Vlan
802 1q
Vlan Trunking
Frame Tagging
Interactive
Streak Sort
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