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114
Note
：
Select
“port
‐
based
VLAN”
in
Advanced
VLAN
Mode
page
before
configuring
port
‐
based
VLAN.
7.3
802.1Q
VLAN
Configuration
Note
：
Select
“802.1Q
VLAN”
in
Advanced
VLAN
Mode
page
before
configuring
802.1Q
VLAN.
7.3.1
802.1Q
VLAN
VLAN
tags
in
the
packets
are
necessary
for
the
switch
to
identify
packets
of
different
VLANs.
The
switch
works
at
Layer
2
and
it
can
identify
the
data
link
layer
encapsulation
of
the
packet
only,
so
you
can
add
the
VLAN
tag
field
into
only
the
data
link
layer
encapsulation
if
necessary.
In
1999,
IEEE
issues
the
IEEE
802.1Q
protocol
to
standardize
VLAN
implementation,
defining
the
structure
of
VLAN
‐
tagged
packets.
In
traditional
Ethernet
data
frames,
the
type
field
of
the
upper
layer
protocol
is
encapsulated
after
the
destination
MAC
address
and
source
MAC
address,
as
shown
in
the
follow
figure
of
Encapsulation
format
of
traditional
Ethernet
frames.
