Kinldy look at the details below for Native Vlan concept explained with examples:
With 802.1Q, a trunk link can tag frames between devices that understand the
protocol. This allows for multiple VLANs to exist on a single topology.
Because 802.1Q is defined as a type of Ethernet frame, it does not require
that every device on a link speaks the 802.1Q protocol. Because Ethernet is
a shared media and more than two device could be connected on this media,
all devices on the link must still be capable of communicating even if they
do not speak the 802.1Q protocol. For this reason, 802.1Q also defines a
Native VLAN. A trunk port on a switch is defined to be in a Native VLAN, and
the 802.1Q trunk will not tag frames that are going out the port that came
in on any port that belongs to the same VLAN that is the Native VLAN on the
switch. Any Ethernet device would be capable of reading frames for the
Native VLANs. The Native VLAN is important on an 802.1Q trunk link. If both
sides of the link do not agree on the Native VLAN, the trunk will not
A Native VLAN is nothing else than a default VLAN given that any port in a
(CISCO)switch has to assigned to one VLAN.
2. The control traffic (vtp/stp/pagp/dtp etc) is untagged and goes via vlan
1 which cant be prune or deleted. If the native vlan ona trunk is also
untagged how does the remote end determine which are contrl packets and
which are data packets belonging to untagged native vlan ?????
Once you change the native VLAN on the switch: say to 999 ( from the default
vlan 1 ) vlan 1 becomes tagged. Only the native vlan ( 999 ) is untagged.
3. By default the native vlan on a trunk is vlan 1 ? correct whats the best
practice not to use this native vlan for trunking ?? I believe the
recommendation is just dont use vlan for anything at all so the only
traffic over that is switch control traffic ?? correct ??
By default Vlan 1 is the native vlan - it is not advisable
to use this for any other traffic. But once you change the native vlan to
say 999 then you can always use vlan 1 for regular traffic as well as this
will now be tagged, this vlan 1 can now be used as a normal tagged vlan. (
Only one vlan is untagged and that is the native vlan ).
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