With an 802.1q trunk link all VLANs EXCEPT the Native VLAN carry a Tag that indicates the VLAN number (as well as the 802.1p priority tag). Packets that are received on a Trunk link WITHOUT an 802.1q Header are treated as received on the VLAN ID that is the Native VLAN. Any packets sent without an 802.1q header should be sourced from the Native VLAN.
Specifying a native VLAN tells the switch or router which VLAN to associate the traffic with, if the traffic that it has received has no VLAN tag.
One use would be to pre-configure a switchport as an 802.1Q VLAN trunk, but also assign a native VLAN. Then, if you plug another switch in that's configured for 802.1Q, it'll trunk; if you plug in a computer or printer that doesn't do 802.1Q tagging, then it'll act like a VLAN access port, sending and receiving on the native VLAN.
Cisco implements 802.1q with native VLAN obligatory - i.e., there HAS to be one VLAN on a 802.1q trunk chosen as a native VLAN (VLAN1 as default).
From IEEE point of view native VLAN is an option on 802.1q trunk.
So some other vendors (3Com, e.g.) allow you to configure a native VLAN, but there is no by default.
Some vendors don't implement native VLAN at all. You need to configure all VLANs on 802.1q trunk to be tagged. There is a set dot1q-all-tagged CatOS command and (but I never tested it) which should enable this feature.
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
Introduction Featured Speakers Luis Espejel is the Telecommunications
Manager of IENova, an Oil & Gas company. Currently he works with Cisco
IOS® and Cisco IOS XE platforms, and NX to some extent. He has also
worked as a Senior Engineer with the Routing P...
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