Why Native VLAN exists on a Trunk?

[cisconetguy]

Basically, A Native VLAN carries untagged traffic on a trunk line.

A trunk line allows mutiple VLAN traffic ( tagged traffic). So Why Native VLAN exists on a trunk.

Why Native VLAN was created?

I'm pretty confused up with VLANs.

[gnijs]

"If both devices are using the trunk the way they should - by properly tagging traffic with the corresponding VLAN tags - why should you be even worried about receiving untagged frames?"

Ha, that is the 1million $ question !!

Because.................some st*pid HP UNIX systems configured in Active/Standby NIC (trunk) teaming, INSIST on sending nic teaming "hello" packets (lan_monitor) untagged on a trunk. Because i followed Cisco recommendations, my native vlan is a local, unused vlan , vlan 999. The result: both NICs (on different switches) don't see each other and nic teaming doesn't work as expected. So now i am forced to implement a spanning native vlan to all server ports to get NIC teaming working (doh?) which i really really don't like....

[Cedar]

Though this is an old post, I found it quite elaborate. Great job Peter!

[asdvads vwe]

Yes, that what I was thinking also.. but it seems that Native VLAN does not have much sense. I would say as Giuseppe said "A Native VLAN is used to connect to a fool device" but I will have to add that even without Native VLAN the Internet and Networks can exist, not in vain Cisco ISL does not support Native VLAN, because it does not really need it. So why then we don't use ISL ? Because ISL frame size exceeds the normal mtu of 1500 bytes. But going back to the Native VLAN, I think that the main purpose of the Native VLAN is that it allows the following protocols: DTP, CDP, VTP, STP to sent the frames on it.

With best regards, 

Stefan