<s>
The	O
VLAN	B-General_Concept
Query	O
Protocol	O
(	O
VQP	B-Protocol
)	O
was	O
developed	O
by	O
Cisco	O
and	O
allows	O
end-devices	O
on	O
LANs	B-General_Concept
to	O
be	O
authenticated	O
via	O
their	O
MAC	O
address	O
and	O
an	O
appropriate	O
VLAN	B-General_Concept
attributed	O
to	O
the	O
port	O
,	O
using	O
a	O
VLAN	B-Protocol
Management	I-Protocol
Policy	I-Protocol
Server	I-Protocol
(	O
VMPS	O
)	O
.	O
</s>
<s>
VQP	B-Protocol
is	O
a	O
Cisco-only	O
protocol	O
that	O
is	O
supported	O
only	O
by	O
older	O
switches	B-Protocol
running	O
CatOS	B-Operating_System
.	O
</s>
<s>
Many	O
vendors	O
(	O
including	O
Cisco	O
)	O
have	O
turned	O
to	O
support	O
dynamic	O
VLAN	B-General_Concept
assignments	O
using	O
the	O
802.1x	O
authentication	O
protocol	O
with	O
a	O
Radius	B-Protocol
server	I-Protocol
that	O
has	O
additional	O
attributes	O
designating	O
the	O
VLAN	B-General_Concept
.	O
</s>
<s>
Upon	O
physically	O
connecting	O
a	O
device	O
to	O
a	O
port	O
of	O
a	O
switch	O
configured	O
as	O
a	O
VLAN	B-Protocol
Management	I-Protocol
Policy	I-Protocol
Server	I-Protocol
(	O
VMPS	O
)	O
client	B-Protocol
,	O
the	O
switch	O
begins	O
listening	O
for	O
packets	B-Protocol
,	O
and	O
encapsulates	O
and	O
rebroadcasts	O
the	O
first	O
packet	B-Protocol
received	O
into	O
a	O
VQP	B-Protocol
packet	B-Protocol
,	O
which	O
is	O
sent	O
to	O
one	O
of	O
up	O
to	O
two	O
configured	O
VMPS	O
servers	O
on	O
port	O
udp/1589	O
.	O
</s>
<s>
The	O
VMPS	O
server	B-Application
will	O
give	O
one	O
of	O
4	O
responses	O
(	O
Allow	O
,	O
Deny	O
,	O
Shutdown	O
,	O
Wrong_Domain	O
)	O
and	O
the	O
switch	O
will	O
either	O
assign	O
the	O
port	O
to	O
the	O
appropriate	O
VLAN	B-General_Concept
,	O
put	O
the	O
port	O
back	O
into	O
the	O
pre-confirmation	O
state	O
,	O
shut	O
down	O
the	O
port	O
until	O
the	O
device	O
or	O
another	O
one	O
is	O
physically	O
reconnected	O
,	O
or	O
log	O
an	O
error	O
indicating	O
that	O
it	O
is	O
incorrectly	O
configured	O
.	O
</s>
<s>
The	O
latter	O
result	O
is	O
often	O
due	O
to	O
Cisco	O
documentation	O
failing	O
to	O
mention	O
that	O
the	O
domain	O
name	O
in	O
the	O
VMPS	O
configuration	O
file	O
must	O
match	O
the	O
VLAN	B-Protocol
Trunking	I-Protocol
Protocol	I-Protocol
(	O
VTP	B-Protocol
)	O
domain	O
name	O
.	O
</s>
<s>
If	O
reconfirmation	O
of	O
VLAN	B-General_Concept
assignment	O
is	O
required	O
,	O
it	O
is	O
done	O
in	O
the	O
same	O
manner	O
as	O
initial	O
confirmation	O
,	O
with	O
the	O
exception	O
of	O
including	O
the	O
currently	O
assigned	O
VLAN	B-General_Concept
for	O
the	O
port	O
in	O
the	O
VQP	B-Protocol
packet	B-Protocol
.	O
</s>
<s>
Reconfirmation	O
is	O
done	O
periodically	O
based	O
on	O
configuration	O
directives	O
of	O
the	O
client	B-Protocol
switches	B-Protocol
,	O
or	O
can	O
be	O
forced	O
with	O
a	O
switch	O
command	O
line	O
directive	O
.	O
</s>
<s>
The	O
VQP	B-Protocol
Protocol	O
has	O
no	O
checksums	B-Algorithm
,	O
encryption	O
or	O
authentication	O
of	O
either	O
the	O
client	B-Protocol
or	O
the	O
switch	O
messages	O
.	O
</s>
<s>
The	O
protocol	O
also	O
does	O
not	O
include	O
scope	O
to	O
send	O
a	O
message	O
to	O
the	O
server	B-Application
informing	O
that	O
a	O
device	O
has	O
been	O
disconnected	O
.	O
</s>
