what is the main function of the native vlan in L2 and L3 ?

[sultanalenazi]

HELLO EVERY ONE

WHAT IS THE MAIN FUNCTION OF THE NATIVE VLAN IN L2 AND L3 ?

[MHM Cisco World]

To be honest' there is no any reason use NATIVE vlan. All other vendor dont use native vlan except cisco.

NOTE:- you can change the default non-tag vlan (native vlan) by add command in global or under interface.

MHM

[RedNectar]

Hi @sultanalenazi ,

I wrote an article about this in response to a similar question on the Cisco Learning Network forum in 2012. Unfortunately, Cisco have seen it fit to kill that forum, so I'll share the link to another page where I wrote the same reply.

[Gopinath_Pigili]

Hello sultanalenazi ,

802.1Q also defines one special VLAN ID on each trunk as the native VLAN (defaulting to use VLAN 1).

By definition, 802.1Q simply does not add an 802.1Q header to frames in the native VLAN. When the switch on the other side of the trunk receives a frame that does not have an 802.1Q header, the receiving switch knows that the frame is part of the native VLAN.

Note: that because of this behavior, both switches must agree on which VLAN is the native VLAN.

The native VLAN concept gives switches the capability of at least passing traffic in one VLAN (the native VLAN), which can allow somebasic functions, like reachability to telnet into a switch.

Best regards
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[Ruben Cocheno]

@sultanalenazi 

In networking, the term "native VLAN" typically refers to a concept in Ethernet networking and is associated with VLANs (Virtual Local Area Networks). The main functions of the native VLAN can vary depending on whether you are referring to Layer 2 (L2) or Layer 3 (L3) networking.

1. Layer 2 (L2):

   • Traffic Untagged: In Layer 2 Ethernet networks, the native VLAN is used to carry untagged traffic. When a device sends traffic on the native VLAN, the Ethernet frames are not tagged with VLAN information. This can be important in scenarios where legacy devices or devices that don't support VLAN tagging need to communicate.

   • Interoperability: The native VLAN helps in interoperability between devices that are part of the same VLAN but may not support VLAN tagging. It ensures that they can communicate without the need for VLAN tags.

   • Trunk Port Default: On a trunk link (a link that carries traffic for multiple VLANs), one VLAN is usually designated as the native VLAN. Frames for this VLAN are transmitted without any VLAN tag.

2. Layer 3 (L3):

   • In Layer 3 networking, the concept of a native VLAN is not directly applicable, as VLANs are more of a Layer 2 construct. Layer 3 deals with IP addresses and routing.

   • In the context of Layer 3, the focus is on IP addressing, subnetting, and routing. The concept of the native VLAN is specific to Layer 2 Ethernet networks where VLANs are used to segment broadcast domains.

In summary, the main function of the native VLAN in Layer 2 is to handle untagged traffic, ensuring compatibility and communication between devices that do not support VLAN tagging. In Layer 3, the concept of a native VLAN is not directly relevant as it pertains to the Layer 2 domain.

[Joseph W. Doherty]

As used in a Cisco environment?

If so, as far as I know, it's not applicable to L3.

For L2, Cisco trunk ports, which can carry multiple VLANs, use "native" to denote what VLAN frames belong to that are untagged.  A trunk port will send the native VLAN frames untagged but can accept that VLAN's frames untagged or tagged.

Why does Cisco support this?

I believe for compatibility when VLAN tagged frames were a "new", i.e. pre .Q, see Cisco proprietary ISL.

[Richard Burts]

As several of my colleagues have pointed out, native vlan relates to trunking, which is a layer 2 thing. When sending Ethernet frames using the trunk a tag is added to the frame which specifies which vlan it belongs to. The concept of native vlan is that for one vlan frames do not have a tag, which is done to provide compatibility for devices that may connect to the trunk but that do not understand the tag and how to process it.

There is no function at layer 3 for native vlan.

[Ruben Cocheno]

@sultanalenazi 

In networking, the term "native VLAN" typically refers to a concept in Ethernet networking and is associated with VLANs (Virtual Local Area Networks). The main functions of the native VLAN can vary depending on whether you are referring to Layer 2 (L2) or Layer 3 (L3) networking.

1. Layer 2 (L2):

   • Traffic Untagged: In Layer 2 Ethernet networks, the native VLAN is used to carry untagged traffic. When a device sends traffic on the native VLAN, the Ethernet frames are not tagged with VLAN information. This can be important in scenarios where legacy devices or devices that don't support VLAN tagging need to communicate.

   • Interoperability: The native VLAN helps in interoperability between devices that are part of the same VLAN but may not support VLAN tagging. It ensures that they can communicate without the need for VLAN tags.

   • Trunk Port Default: On a trunk link (a link that carries traffic for multiple VLANs), one VLAN is usually designated as the native VLAN. Frames for this VLAN are transmitted without any VLAN tag.

2. Layer 3 (L3):

   • In Layer 3 networking, the concept of a native VLAN is not directly applicable, as VLANs are more of a Layer 2 construct. Layer 3 deals with IP addresses and routing.

   • In the context of Layer 3, the focus is on IP addressing, subnetting, and routing. The concept of the native VLAN is specific to Layer 2 Ethernet networks where VLANs are used to segment broadcast domains.

In summary, the main function of the native VLAN in Layer 2 is to handle untagged traffic, ensuring compatibility and communication between devices that do not support VLAN tagging. In Layer 3, the concept of a native VLAN is not directly relevant as it pertains to the Layer 2 domain.