<s>
In	O
computing	O
,	O
a	O
router	B-Protocol
on	I-Protocol
a	I-Protocol
stick	I-Protocol
,	O
also	O
known	O
as	O
a	O
one-armed	B-Protocol
router	I-Protocol
,	O
is	O
a	O
router	B-Protocol
that	O
has	O
a	O
single	O
physical	O
or	O
logical	O
connection	O
to	O
a	O
network	O
.	O
</s>
<s>
It	O
is	O
a	O
method	O
of	O
inter-VLAN	O
(	O
virtual	B-General_Concept
local	I-General_Concept
area	I-General_Concept
networks	I-General_Concept
)	O
routing	O
where	O
one	O
router	B-Protocol
is	O
connected	O
to	O
a	O
switch	B-Protocol
via	O
a	O
single	O
cable	O
.	O
</s>
<s>
The	O
router	B-Protocol
has	O
physical	O
connections	O
to	O
the	O
broadcast	B-Architecture
domains	I-Architecture
where	O
one	O
or	O
more	O
VLANs	B-General_Concept
require	O
the	O
need	O
for	O
routing	O
between	O
them	O
.	O
</s>
<s>
Devices	O
on	O
separate	O
VLANs	B-General_Concept
or	O
in	O
a	O
typical	O
LAN	B-General_Concept
(	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
)	O
are	O
unable	O
to	O
communicate	O
with	O
each	O
other	O
.	O
</s>
<s>
Therefore	O
,	O
it	O
is	O
often	O
used	O
to	O
forward	O
traffic	O
between	O
locally	O
attached	O
hosts	O
on	O
separate	O
logical	O
routing	B-Protocol
domains	I-Protocol
or	O
to	O
facilitate	O
routing	B-Protocol
table	I-Protocol
administration	O
,	O
distribution	O
and	O
relay	O
.	O
</s>
<s>
One-armed	B-Protocol
routers	I-Protocol
that	O
perform	O
traffic	O
forwarding	O
are	O
often	O
implemented	O
on	O
virtual	B-General_Concept
local	I-General_Concept
area	I-General_Concept
networks	I-General_Concept
(	O
VLANs	B-General_Concept
)	O
.	O
</s>
<s>
They	O
use	O
a	O
single	O
Ethernet	O
network	O
interface	O
port	O
that	O
is	O
part	O
of	O
two	O
or	O
more	O
Virtual	B-General_Concept
LANs	I-General_Concept
,	O
enabling	O
them	O
to	O
be	O
joined	O
.	O
</s>
<s>
A	O
VLAN	B-General_Concept
allows	O
multiple	O
virtual	B-General_Concept
LANs	I-General_Concept
to	O
coexist	O
on	O
the	O
same	O
physical	O
LAN	B-General_Concept
.	O
</s>
<s>
This	O
means	O
that	O
two	O
machines	O
attached	O
to	O
the	O
same	O
switch	B-Protocol
cannot	O
send	O
Ethernet	B-Protocol
frames	I-Protocol
to	O
each	O
other	O
even	O
though	O
they	O
pass	O
over	O
the	O
same	O
wires	O
.	O
</s>
<s>
If	O
they	O
need	O
to	O
communicate	O
,	O
then	O
a	O
router	B-Protocol
must	O
be	O
placed	O
between	O
the	O
two	O
VLANs	B-General_Concept
to	O
forward	O
packets	B-Protocol
,	O
just	O
as	O
if	O
the	O
two	O
LANs	B-General_Concept
were	O
physically	O
isolated	O
.	O
</s>
<s>
The	O
only	O
difference	O
is	O
that	O
the	O
router	B-Protocol
in	O
question	O
may	O
contain	O
only	O
a	O
single	O
Ethernet	O
network	B-Protocol
interface	I-Protocol
controller	I-Protocol
(	O
NIC	O
)	O
that	O
is	O
part	O
of	O
both	O
VLANs	B-General_Concept
.	O
</s>
<s>
A	O
one-armed	B-Protocol
router	I-Protocol
could	O
be	O
assigned	O
addresses	O
for	O
each	O
network	O
and	O
be	O
used	O
to	O
forward	O
traffic	O
between	O
locally	O
distinct	O
networks	O
and	O
to	O
remote	O
networks	O
through	O
another	O
gateway	O
.	O
</s>
<s>
One-armed	B-Protocol
routers	I-Protocol
are	O
also	O
used	O
for	O
administration	O
purposes	O
such	O
as	O
route	O
collection	O
,	O
multi	O
hop	O
relay	O
and	O
looking	B-Application
glass	I-Application
servers	I-Application
.	O
</s>
<s>
An	O
example	O
of	O
router	B-Protocol
on	I-Protocol
a	I-Protocol
stick	I-Protocol
usage	O
is	O
found	O
in	O
Call	O
Manager	O
Express	O
installation	O
,	O
when	O
the	O
Voice	B-Application
over	I-Application
IP	I-Application
network	O
and	O
Cisco	O
IP	O
phone	O
devices	O
have	O
a	O
need	O
to	O
split	O
.	O
</s>
<s>
As	O
the	O
network	O
is	O
separated	O
virtually	O
,	O
the	O
router	B-Protocol
does	O
not	O
need	O
to	O
be	O
placed	O
adjacent	O
to	O
the	O
devices	O
,	O
rather	O
is	O
it	O
placed	O
to	O
the	O
side	O
in	O
the	O
network	B-Architecture
topology	I-Architecture
.	O
</s>
<s>
The	O
router	B-Protocol
is	O
connected	O
to	O
the	O
switch	B-Protocol
by	O
a	O
single	O
cable	O
.	O
</s>
<s>
In	O
some	O
institutions	O
,	O
the	O
abbreviation	O
RoaS	O
or	O
ROAS	O
is	O
used	O
instead	O
of	O
router	B-Protocol
on	I-Protocol
a	I-Protocol
stick	I-Protocol
.	O
</s>
<s>
Router	B-Protocol
on	I-Protocol
a	I-Protocol
stick	I-Protocol
relies	O
on	O
one	O
ethernet	O
link	O
that	O
is	O
configured	O
as	O
IEEE	O
802.1Q	O
trunk	O
link	O
.	O
</s>
<s>
The	O
trunk	O
is	O
where	O
data	O
flows	O
for	O
the	O
VLANs	B-General_Concept
.	O
</s>
<s>
Networks	O
that	O
utilise	O
router	B-Protocol
on	I-Protocol
a	I-Protocol
stick	I-Protocol
benefit	O
from	O
only	O
requiring	O
one	O
LAN	B-General_Concept
connection	O
to	O
be	O
used	O
for	O
multiple	O
VLANs	B-General_Concept
,	O
i.e.	O
</s>
<s>
the	O
number	O
of	O
VLANs	B-General_Concept
are	O
not	O
limited	O
by	O
the	O
number	O
of	O
LAN	B-General_Concept
ports	O
available	O
.	O
</s>
<s>
Separation	O
of	O
network	O
connections	O
do	O
not	O
respond	O
to	O
the	O
physical	O
location	O
of	O
the	O
ports	O
on	O
the	O
router	B-Protocol
.	O
</s>
<s>
As	O
VLANs	B-General_Concept
are	O
segmented	O
,	O
it	O
reduces	O
the	O
amount	O
of	O
traffic	O
flow	O
through	O
a	O
connection	O
.	O
</s>
<s>
By	O
separating	O
VLANs	B-General_Concept
,	O
it	O
provides	O
enhanced	O
network	O
security	O
.	O
</s>
<s>
Network	O
administrators	O
have	O
direct	O
control	O
over	O
multiple	O
broadcast	B-Architecture
domains	I-Architecture
.	O
</s>
<s>
In	O
the	O
event	O
of	O
a	O
malicious	O
user	O
attempting	O
to	O
access	O
any	O
switch	B-Protocol
port	I-Protocol
,	O
they	O
will	O
have	O
limited	O
access	O
to	O
the	O
network	O
.	O
</s>
<s>
Certain	O
cases	O
where	O
workgroups	B-Device
are	O
to	O
be	O
created	O
.	O
</s>
<s>
Those	O
outside	O
of	O
the	O
VLANs	B-General_Concept
cannot	O
communicate	O
,	O
therefore	O
departments	O
are	O
made	O
independent	O
from	O
each	O
other	O
.	O
</s>
<s>
Networks	O
via	O
router	B-Protocol
on	I-Protocol
a	I-Protocol
stick	I-Protocol
are	O
independent	O
from	O
their	O
physical	O
locations	O
,	O
therefore	O
sensitive	O
data	O
can	O
be	O
handled	O
without	O
compromise	O
and	O
with	O
ease	O
.	O
</s>
<s>
Changes	O
to	O
networks	O
like	O
adding	O
or	O
removing	O
a	O
broadcast	B-Architecture
domain	I-Architecture
is	O
achievable	O
by	O
assigning	O
hosts	O
to	O
the	O
appropriate	O
VLANs	B-General_Concept
.	O
</s>
<s>
Broadcasts	O
of	O
networks	O
can	O
be	O
managed	O
by	O
multiple	O
hosts	O
,	O
controlled	O
by	O
implementing	O
as	O
many	O
VLANs	B-General_Concept
as	O
required	O
.	O
</s>
<s>
Implementation	O
of	O
this	O
setup	O
only	O
requires	O
one	O
router	B-Protocol
.	O
</s>
<s>
Compared	O
to	O
the	O
alternative	O
of	O
using	O
L3	O
(	O
Layer	O
3	O
switching	O
)	O
,	O
the	O
trunk	O
may	O
become	O
a	O
source	O
of	O
congestion	O
as	O
traffic	O
from	O
all	O
VLANs	B-General_Concept
must	O
flow	O
through	O
the	O
trunk	O
link	O
.	O
</s>
<s>
Modern	O
networks	O
utilise	O
L3	O
switch	B-Protocol
which	O
provides	O
greater	O
bandwidth	O
output	O
and	O
functionality	O
.	O
</s>
<s>
Bottleneck	O
can	O
be	O
mitigated	O
if	O
the	O
single	O
interface	O
is	O
combined	O
with	O
other	O
interfaces	O
via	O
link	B-Architecture
aggregation	I-Architecture
.	O
</s>
<s>
If	O
the	O
router	B-Protocol
fails	O
,	O
there	O
is	O
no	O
backup	O
and	O
that	O
may	O
become	O
the	O
bottleneck	O
in	O
the	O
network	O
.	O
</s>
<s>
Since	O
all	O
VLANs	B-General_Concept
must	O
traverse	O
one	O
router	B-Protocol
,	O
there	O
is	O
a	O
great	O
potential	O
in	O
insufficient	O
bandwidth	O
provided	O
for	O
all	O
network	O
connections	O
.	O
</s>
<s>
Additional	O
latency	O
may	O
be	O
induced	O
when	O
connecting	O
the	O
switch	B-Protocol
to	O
the	O
router	B-Protocol
.	O
</s>
<s>
Layer	O
3	O
switches	O
can	O
route	O
traffic	O
to	O
other	O
switches	O
without	O
the	O
need	O
for	O
a	O
router	B-Protocol
.	O
</s>
<s>
It	O
processes	O
data	B-Protocol
packets	I-Protocol
faster	O
than	O
routers	B-Protocol
since	O
the	O
data	O
traverses	O
wire	O
speed	O
.	O
</s>
