vlan id

Unanswered Question
Jun 22nd, 2007

Hi all, I have had to manage another none cisco switch today, I came across an option where you have to put the port in the vlan, and then make sure its vlan id is the same, firstly what is the vlan id used for?? also there was a command saying default vlan id, what is this for? is this the same as the native vlan ?

I have this problem too.
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abdel_n Fri, 06/22/2007 - 07:31


Here is a brief explanation:

To implement VLANs, switch vendors refer to IEEE standard 802.1q, the non-proprietary protocol.

VLAN is used to separate between different group of end-user ports at the layer 2 and reduce broadcasting domains.

To do so, 802.1q add a tag to the layer 2 frame and recalculate the CRC to indicate that it belongs to a specific VLAN when forwarding to another end-user port or through trunk links connected to other switches.

The tag is composed of several fields among them the( VLAN ID) field which will contain the VLAN number you assigned to a particular port.

So I guess independently of what switch you are using, if it supports 802.1q VLANs, you will have to map different switch ports to different VLANs (vlan ID = VLAN number) according to your planned design. Also for trunk links you have to assign a native VLAN (if it?s not done by default or you have to change it).

Maybe your switch propose to set a VLAN ID to which ports are mapped by default, this can be an additional security feature when the vlan is unused.

I recommend you to get the configuration guide for your given switch for more details about VLAN implementation.

Good work,



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