native vlan

mcse_696

hi all
Whats the concept of native vlan? , when all vlans passing through a trunk port tagged using protocol 802.1Q ,

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/usr

The native VLAN is the default VLAN in which ALL network communication takes place. On Cisco equipment, it is VLAN 1.

I believe that packets in the default VLAN are not tagged, by default.

LBC90805

mcse_696 wrote: »

hi all
Whats the concept of native vlan? , when all vlans passing through a trunk port tagged using protocol 802.1Q ,

The concept of the Native VLAN was support for ports that were hooked into Shared Bandwidth Hubs that we also unmanaged! Thus the host on those hubs would not be in a tagged VLAN, a VLAN other than the Native VLAN.

rwwest7

I thought the native VLAN was for all traffic that was not tagged for any other VLAN. By default VLAN 1, so if you just pull a switch out of the box and plug it in then everything is in VLAN 1 until you configure other VLANs.

gojericho0

Inter-Switch Link and IEEE 802.1Q Frame Format - Cisco Systems

wbosher

The native VLAN is also useful when you have a PC and an IP phone on the same port, as is more often the case these days.

The interface is configured as a trunk, and the IP phone is assigned to a voice VLAN but the PC is on the native VLAN. The IP phone tags it packets with a VLAN number but the PC doesn't. I think that's how it works.

/usr

The IP phone tags it packets with a VLAN number but the PC doesn't. I think that's how it works.

That is correct.

Our switches will "autoconfigure" switchports for the voice VLAN by looking at the OUI in the MAC address. If it sees a phone OUI, it places the switchport in the voice VLAN, but still leaves it in the native VLAN as well. The phone tags it's packets and the PC communicates in the native VLAN.