Root: WRM Database > Information Technology > Certifications > CCNA > VLANs > VLAN Trunking > Protocols > 802.1Q > Native VLAN > What Is 802.1Q Native VLAN?
Root: WRM Database > Information Technology > Certifications > CCNA > VLANs > VLAN Trunking > Protocols > 802.1Q > VLAN Header > What Is 802.1Q Native VLAN?
The native VLAN ID can be manually set to different VLANs on either end of the trunk. If the native VLANs differ, the switches will accidentally cause frames to leave one VLAN and enter another. For example, if switch SW1 sends a frame using native VLAN 1 on an 802.1Q trunk, SW1 does not add a VLAN header, as is normal for the native VLAN. When switch SW2 receives the frame, noticing that no 802.1Q header exists, SW2 assumes that the frame is part of SW2's configured native VLAN. If SW2 has been configured to think VLAN 2 is the native VLAN on that trunk. SW2 will try to forward the received frame into VLAN 2.
Odom, Wendell (2008) CCNA ICND2 Official Exam Certification Guide, Second Edition. Indianapolis: Cisco Press.