<s>
Port	B-Protocol
mirroring	I-Protocol
is	O
used	O
on	O
a	O
network	B-Protocol
switch	I-Protocol
to	O
send	O
a	O
copy	O
of	O
network	B-Protocol
packets	I-Protocol
seen	O
on	O
one	O
switch	B-Protocol
port	I-Protocol
(	O
or	O
an	O
entire	O
VLAN	B-General_Concept
)	O
to	O
a	O
network	B-Architecture
monitoring	O
connection	O
on	O
another	O
switch	B-Protocol
port	I-Protocol
.	O
</s>
<s>
This	O
is	O
commonly	O
used	O
for	O
network	B-Architecture
appliances	O
that	O
require	O
monitoring	O
of	O
network	B-Architecture
traffic	O
such	O
as	O
an	O
intrusion	O
detection	O
system	O
,	O
passive	O
probe	O
or	O
real	O
user	O
monitoring	O
(	O
RUM	O
)	O
technology	O
that	O
is	O
used	O
to	O
support	O
application	B-Application
performance	I-Application
management	I-Application
(	O
APM	O
)	O
.	O
</s>
<s>
Port	B-Protocol
mirroring	I-Protocol
on	O
a	O
Cisco	O
Systems	O
switch	O
is	O
generally	O
referred	O
to	O
as	O
Switched	B-Protocol
Port	I-Protocol
Analyzer	I-Protocol
(	O
SPAN	O
)	O
or	O
Remote	B-Protocol
Switched	I-Protocol
Port	I-Protocol
Analyzer	I-Protocol
(	O
RSPAN	B-Protocol
)	O
.	O
</s>
<s>
Other	O
vendors	O
have	O
different	O
names	O
for	O
it	O
,	O
such	O
as	O
Roving	O
Analysis	O
Port	B-Protocol
(	O
RAP	O
)	O
on	O
3Com	O
switches	O
.	O
</s>
<s>
Network	B-Architecture
engineers	O
or	O
administrators	O
use	O
port	B-Protocol
mirroring	I-Protocol
to	O
analyze	O
and	O
debug	O
data	O
or	O
diagnose	O
errors	O
on	O
a	O
network	B-Architecture
.	O
</s>
<s>
It	O
helps	O
administrators	O
keep	O
a	O
close	O
eye	O
on	O
network	B-Architecture
performance	O
and	O
alerts	O
them	O
when	O
problems	O
occur	O
.	O
</s>
<s>
It	O
can	O
be	O
used	O
to	O
mirror	O
either	O
inbound	O
or	O
outbound	O
traffic	O
(	O
or	O
both	O
)	O
on	O
single	O
or	O
multiple	O
interfaces	B-Protocol
.	O
</s>
