Access/Untagged & native ports

[xs2sachin]

In cisco we can make only one vlan as access vlan which seems to be logical...

but in any other switches we can make multiple vlans as untagged vlans...can someone elaborate upon this...

but still hosts can communicate only on the vlan which is untagged & native both..what about the other vlans which are untagged but not native...

[sourabhagarwal]

you can configure switchport as access or trunk port.

Access port is the one which carries only 1 VLAN information.

Trunk port carries information from multiple VLAN. In trunk port, there is a concept of native or untagged VLAN and tagged VLAN.

Native VLAN are the VLAN for which information won't be tagged while using 802.1Q trunking protocol. While tagged VLAns are tjose whose information is tagged using 802.1q trunking protocol.

hope it helps ... rate if it does ....

[xs2sachin]

My query is when we can configure multiple vlans as untagged vlans but only one vlan as native....what is the use of having multiple vlans untagged when we can't make traffic folw on all of them...

I want to understand this for 802.1q not cisco

[sourabhagarwal]

Traffic flow on all VLANs including tagged and untagged VLANs.

In 802.1Q, you can configure only one VLAN as native VLAN for which traffic will be untagged but for other VLANs traffic will be tagged.

you can use this concept when you are connecting switches using a trunk port or you are connecting PC and phone to a trunk port where you will configure PC VLAN as native and phone as voice VLAN. In both cases traffic will flow for all VLANs.

check this URL in case you need more information.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800ca801.html

hope it will clear your doubt. rate if it does ...

[xs2sachin]

We will take one example

the following is my show interface command

interface ethernet 1/21

switchport allowed vlan add 100,101,103 tagged

switchportallowed vlan add 501,502,503 unntagged

switchport native vlan 501

here we are able to untagg multiple vlans on the interface ie 502 and 503 but traffic can't flow on that. Traffic flows only on the native vlan

so whats the use of untagging vlans if it is not made native.