<s>
NetFlow	B-Protocol
is	O
a	O
feature	O
that	O
was	O
introduced	O
on	O
Cisco	O
routers	B-Protocol
around	O
1996	O
that	O
provides	O
the	O
ability	O
to	O
collect	O
IP	B-Protocol
network	O
traffic	O
as	O
it	O
enters	O
or	O
exits	O
an	O
interface	O
.	O
</s>
<s>
By	O
analyzing	O
the	O
data	O
provided	O
by	O
NetFlow	B-Protocol
,	O
a	O
network	O
administrator	O
can	O
determine	O
things	O
such	O
as	O
the	O
source	O
and	O
destination	O
of	O
traffic	O
,	O
class	O
of	O
service	O
,	O
and	O
the	O
causes	O
of	O
congestion	O
.	O
</s>
<s>
A	O
typical	O
flow	O
monitoring	O
setup	O
(	O
using	O
NetFlow	B-Protocol
)	O
consists	O
of	O
three	O
main	O
components	O
:	O
</s>
<s>
Routers	B-Protocol
and	O
switches	O
that	O
support	O
NetFlow	B-Protocol
can	O
collect	O
IP	B-Protocol
traffic	O
statistics	O
on	O
all	O
interfaces	O
where	O
NetFlow	B-Protocol
is	O
enabled	O
,	O
and	O
later	O
export	O
those	O
statistics	O
as	O
NetFlow	B-Protocol
records	O
toward	O
at	O
least	O
one	O
NetFlow	B-Protocol
collector	O
—	O
typically	O
a	O
server	O
that	O
does	O
the	O
actual	O
traffic	O
analysis	O
.	O
</s>
<s>
Cisco	O
standard	O
NetFlow	B-Protocol
version	O
5	O
defines	O
a	O
flow	O
as	O
a	O
unidirectional	O
sequence	O
of	O
packets	O
that	O
all	O
share	O
seven	O
values	O
which	O
define	O
a	O
unique	O
key	O
for	O
the	O
flow	O
:	O
</s>
<s>
Note	O
that	O
the	O
Egress	O
interface	O
,	O
IP	B-Protocol
Nexthop	O
or	O
BGP	O
Nexthops	O
are	O
not	O
part	O
of	O
the	O
key	O
,	O
and	O
may	O
not	O
be	O
accurate	O
if	O
the	O
route	O
changes	O
before	O
the	O
expiration	O
of	O
the	O
flow	O
,	O
or	O
if	O
load-balancing	O
is	O
done	O
per-packet	O
.	O
</s>
<s>
This	O
definition	O
of	O
flows	O
is	O
also	O
used	O
for	O
IPv6	B-Protocol
,	O
and	O
a	O
similar	O
definition	O
is	O
used	O
for	O
MPLS	B-Protocol
and	O
Ethernet	B-Protocol
flows	O
.	O
</s>
<s>
Advanced	O
NetFlow	B-Protocol
or	O
IPFIX	B-Protocol
implementations	O
like	O
Cisco	O
Flexible	O
NetFlow	B-Protocol
allow	O
user-defined	O
flow	O
keys	O
.	O
</s>
<s>
A	O
typical	O
output	O
of	O
a	O
NetFlow	B-Protocol
command	O
line	O
tool	O
(	O
nfdump	O
in	O
this	O
case	O
)	O
when	O
printing	O
the	O
stored	O
flows	O
may	O
look	O
as	O
follows	O
:	O
</s>
<s>
The	O
router	B-Protocol
will	O
output	O
a	O
flow	O
record	O
when	O
it	O
determines	O
that	O
the	O
flow	O
is	O
finished	O
.	O
</s>
<s>
It	O
does	O
this	O
by	O
flow	O
aging	O
:	O
when	O
the	O
router	B-Protocol
sees	O
new	O
traffic	O
for	O
an	O
existing	O
flow	O
it	O
resets	O
the	O
aging	O
counter	O
.	O
</s>
<s>
Also	O
,	O
TCP	B-Protocol
session	O
termination	O
in	O
a	O
TCP	B-Protocol
flow	O
causes	O
the	O
router	B-Protocol
to	O
expire	O
the	O
flow	O
.	O
</s>
<s>
Routers	B-Protocol
can	O
also	O
be	O
configured	O
to	O
output	O
a	O
flow	O
record	O
at	O
a	O
fixed	O
interval	O
even	O
if	O
the	O
flow	O
is	O
still	O
ongoing	O
.	O
</s>
<s>
NetFlow	B-Protocol
records	O
are	O
traditionally	O
exported	O
using	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
(	O
UDP	B-Protocol
)	O
and	O
collected	O
using	O
a	O
NetFlow	B-Protocol
collector	O
.	O
</s>
<s>
The	O
IP	B-Protocol
address	I-Protocol
of	O
the	O
NetFlow	B-Protocol
collector	O
and	O
the	O
destination	O
UDP	B-Protocol
port	O
must	O
be	O
configured	O
on	O
the	O
sending	O
router	B-Protocol
.	O
</s>
<s>
A	O
common	O
value	O
is	O
UDP	B-Protocol
port	O
2055	O
,	O
but	O
other	O
values	O
like	O
9555	O
or	O
9995	O
,	O
9025	O
,	O
9026	O
etc	O
.	O
</s>
<s>
For	O
efficiency	O
reasons	O
,	O
the	O
router	B-Protocol
traditionally	O
does	O
not	O
keep	O
track	O
of	O
flow	O
records	O
already	O
exported	O
,	O
so	O
if	O
a	O
NetFlow	B-Protocol
packet	O
is	O
dropped	O
due	O
to	O
network	B-Protocol
congestion	I-Protocol
or	O
packet	O
corruption	O
,	O
all	O
contained	O
records	O
are	O
lost	O
forever	O
.	O
</s>
<s>
The	O
UDP	B-Protocol
protocol	I-Protocol
does	O
not	O
inform	O
the	O
router	B-Protocol
of	O
the	O
loss	O
so	O
it	O
can	O
send	O
the	O
packets	O
again	O
.	O
</s>
<s>
This	O
can	O
be	O
a	O
real	O
problem	O
,	O
especially	O
with	O
NetFlow	B-Protocol
v8	O
or	O
v9	O
that	O
can	O
aggregate	O
a	O
lot	O
of	O
packets	O
or	O
flows	O
into	O
a	O
single	O
record	O
.	O
</s>
<s>
A	O
single	O
UDP	B-Protocol
packet	I-Protocol
loss	O
can	O
cause	O
a	O
huge	O
impact	O
on	O
the	O
statistics	O
of	O
some	O
flows	O
.	O
</s>
<s>
That	O
is	O
why	O
some	O
modern	O
implementations	O
of	O
NetFlow	B-Protocol
use	O
the	O
Stream	B-Protocol
Control	I-Protocol
Transmission	I-Protocol
Protocol	I-Protocol
(	O
SCTP	B-Protocol
)	O
to	O
export	O
packets	O
so	O
as	O
to	O
provide	O
some	O
protection	O
against	O
packet	O
loss	O
,	O
and	O
make	O
sure	O
that	O
NetFlow	B-Protocol
v9	O
templates	O
are	O
received	O
before	O
any	O
related	O
record	O
is	O
exported	O
.	O
</s>
<s>
Note	O
that	O
TCP	B-Protocol
would	O
not	O
be	O
suitable	O
for	O
NetFlow	B-Protocol
because	O
a	O
strict	O
ordering	O
of	O
packets	O
would	O
cause	O
excessive	O
buffering	O
and	O
delays	O
.	O
</s>
<s>
The	O
problem	O
with	O
SCTP	B-Protocol
is	O
that	O
it	O
requires	O
interaction	O
between	O
each	O
NetFlow	B-Protocol
collector	O
and	O
each	O
router	B-Protocol
exporting	O
NetFlow	B-Protocol
.	O
</s>
<s>
There	O
may	O
be	O
performance	O
limitations	O
if	O
a	O
router	B-Protocol
has	O
to	O
deal	O
with	O
many	O
NetFlow	B-Protocol
collectors	O
,	O
and	O
a	O
NetFlow	B-Protocol
collector	O
has	O
to	O
deal	O
with	O
many	O
routers	B-Protocol
,	O
especially	O
when	O
some	O
of	O
them	O
are	O
unavailable	O
due	O
to	O
failure	O
or	O
maintenance	O
.	O
</s>
<s>
SCTP	B-Protocol
may	O
not	O
be	O
efficient	O
if	O
NetFlow	B-Protocol
must	O
be	O
exported	O
toward	O
several	O
independent	O
collectors	O
,	O
some	O
of	O
which	O
may	O
be	O
test	O
servers	O
that	O
can	O
go	O
down	O
at	O
any	O
moment	O
.	O
</s>
<s>
UDP	B-Protocol
allows	O
simple	O
replication	O
of	O
NetFlow	B-Protocol
packets	O
using	O
Network	O
taps	O
or	O
L2	O
or	O
L3	O
Mirroring	O
.	O
</s>
<s>
Simple	O
stateless	O
equipment	O
can	O
also	O
filter	O
or	O
change	O
the	O
destination	O
address	O
of	O
NetFlow	B-Protocol
UDP	B-Protocol
packets	I-Protocol
if	O
necessary	O
.	O
</s>
<s>
Since	O
NetFlow	B-Protocol
export	O
almost	O
only	O
use	O
network	O
backbone	O
links	O
,	O
packet	O
loss	O
will	O
often	O
be	O
negligible	O
.	O
</s>
<s>
If	O
it	O
happens	O
,	O
it	O
will	O
mostly	O
be	O
on	O
the	O
link	O
between	O
the	O
network	O
and	O
the	O
NetFlow	B-Protocol
collectors	O
.	O
</s>
<s>
All	O
NetFlow	B-Protocol
packets	O
begin	O
with	O
version-dependent	O
header	O
,	O
that	O
contains	O
at	O
least	O
these	O
fields	O
:	O
</s>
<s>
A	O
NetFlow	B-Protocol
record	O
can	O
contain	O
a	O
wide	O
variety	O
of	O
information	O
about	O
the	O
traffic	O
in	O
a	O
given	O
flow	O
.	O
</s>
<s>
NetFlow	B-Protocol
version	O
5	O
(	O
one	O
of	O
the	O
most	O
commonly	O
used	O
versions	O
,	O
followed	O
by	O
version	O
9	O
)	O
contains	O
the	O
following	O
:	O
</s>
<s>
Input	O
interface	O
index	O
used	O
by	O
SNMP	B-Protocol
(	O
ifIndex	O
in	O
IF-MIB	O
)	O
.	O
</s>
<s>
Layer	B-Application
3	I-Application
headers	O
:	O
</s>
<s>
ICMP	B-Protocol
Type	O
and	O
Code	O
.	O
</s>
<s>
For	O
TCP	B-Protocol
flows	O
,	O
the	O
union	O
of	O
all	O
TCP	B-Protocol
flags	O
observed	O
over	O
the	O
life	O
of	O
the	O
flow	O
.	O
</s>
<s>
Layer	B-Application
3	I-Application
Routing	B-Protocol
information	I-Protocol
:	O
</s>
<s>
For	O
ICMP	B-Protocol
flows	O
,	O
the	O
Source	O
Port	O
is	O
zero	O
,	O
and	O
the	O
Destination	O
Port	O
number	O
field	O
codes	O
ICMP	B-Protocol
message	O
Type	O
and	O
Code	O
(	O
port	O
=	O
ICMP-Type	O
*	O
256	O
+	O
ICMP-Code	O
)	O
.	O
</s>
<s>
The	O
source	O
and	O
destination	O
Autonomous	B-Architecture
System	I-Architecture
(	O
AS	O
)	O
number	O
fields	O
can	O
report	O
the	O
destination	O
AS	O
(	O
last	O
AS	O
of	O
AS-Path	O
)	O
or	O
the	O
immediate	O
neighbor	O
AS	O
(	O
first	O
AS	O
of	O
AS-Path	O
)	O
depending	O
on	O
the	O
router	B-Protocol
configuration	O
.	O
</s>
<s>
But	O
the	O
AS	B-Architecture
number	I-Architecture
will	O
be	O
zero	O
if	O
the	O
feature	O
is	O
not	O
supported	O
,	O
the	O
route	O
is	O
unknown	O
or	O
not	O
announced	O
by	O
BGP	O
,	O
or	O
the	O
AS	O
is	O
the	O
local	O
AS	O
.	O
</s>
<s>
NetFlow	B-Protocol
version	O
9	O
can	O
include	O
all	O
of	O
these	O
fields	O
and	O
can	O
optionally	O
include	O
additional	O
information	O
such	O
as	O
Multiprotocol	B-Protocol
Label	I-Protocol
Switching	I-Protocol
(	O
MPLS	B-Protocol
)	O
labels	O
and	O
IPv6	B-Protocol
addresses	O
and	O
ports	O
,	O
</s>
<s>
By	O
analyzing	O
flow	O
data	O
,	O
a	O
picture	O
of	O
traffic	B-Operating_System
flow	I-Operating_System
and	O
traffic	O
volume	O
in	O
a	O
network	O
can	O
be	O
built	O
.	O
</s>
<s>
The	O
NetFlow	B-Protocol
record	O
format	O
has	O
evolved	O
over	O
time	O
,	O
hence	O
the	O
inclusion	O
of	O
version	O
numbers	O
.	O
</s>
<s>
NetFlow	B-Protocol
is	O
usually	O
enabled	O
on	O
a	O
per-interface	O
basis	O
to	O
limit	O
load	O
on	O
the	O
router	B-Protocol
components	O
involved	O
in	O
NetFlow	B-Protocol
,	O
or	O
to	O
limit	O
the	O
amount	O
of	O
NetFlow	B-Protocol
records	O
exported	O
.	O
</s>
<s>
NetFlow	B-Protocol
usually	O
captures	O
all	O
packets	O
received	O
by	O
an	O
ingress	O
IP	B-Protocol
interface	O
,	O
but	O
some	O
NetFlow	B-Protocol
implementations	O
use	O
IP	B-Protocol
filters	O
to	O
decide	O
if	O
a	O
packet	O
can	O
be	O
observed	O
by	O
NetFlow	B-Protocol
.	O
</s>
<s>
Some	O
NetFlow	B-Protocol
implementations	O
also	O
allow	O
the	O
observation	O
of	O
packets	O
on	O
the	O
egress	O
IP	B-Protocol
interface	O
,	O
but	O
this	O
must	O
be	O
used	O
with	O
care	O
:	O
all	O
flows	O
from	O
any	O
ingress	O
interface	O
with	O
NetFlow	B-Protocol
enabled	O
to	O
any	O
interface	O
with	O
NetFlow	B-Protocol
enabled	O
could	O
be	O
counted	O
twice	O
.	O
</s>
<s>
Standard	O
NetFlow	B-Protocol
was	O
designed	O
to	O
process	O
all	O
IP	B-Protocol
packets	O
on	O
an	O
interface	O
.	O
</s>
<s>
So	O
Cisco	O
introduced	O
sampled	O
NetFlow	B-Protocol
on	O
Cisco	B-Device
12000	I-Device
,	O
and	O
that	O
is	O
now	O
used	O
in	O
all	O
high-end	O
routers	B-Protocol
that	O
implement	O
NetFlow	B-Protocol
.	O
</s>
<s>
Only	O
one	O
packet	O
out	O
of	O
n	O
is	O
processed	O
,	O
where	O
n	O
,	O
the	O
sampling	O
rate	O
,	O
is	O
determined	O
by	O
the	O
router	B-Protocol
configuration	O
.	O
</s>
<s>
One	O
packet	O
every	O
n	O
packet	O
,	O
in	O
Deterministic	O
NetFlow	B-Protocol
,	O
as	O
used	O
on	O
Cisco	O
's	O
12000	B-Device
.	O
</s>
<s>
One	O
packet	O
randomly	O
selected	O
in	O
an	O
interval	O
of	O
n	O
packet	O
,	O
in	O
Random	O
Sampled	O
NetFlow	B-Protocol
,	O
used	O
on	O
modern	O
Cisco	O
routers	B-Protocol
.	O
</s>
<s>
Some	O
implementations	O
have	O
more	O
complex	O
methods	O
to	O
sample	O
packets	O
,	O
like	O
per-flow	O
sampling	O
on	O
Cisco	O
Martinez	O
Catalysts	B-Device
.	O
</s>
<s>
The	O
sampling	O
rate	O
is	O
often	O
the	O
same	O
for	O
all	O
interfaces	O
,	O
but	O
can	O
be	O
adjusted	O
per	O
interface	O
for	O
some	O
routers	B-Protocol
.	O
</s>
<s>
When	O
Sampled	O
NetFlow	B-Protocol
is	O
used	O
,	O
the	O
NetFlow	B-Protocol
records	O
must	O
be	O
adjusted	O
for	O
the	O
effect	O
of	O
sampling	O
-	O
traffic	O
volumes	O
,	O
in	O
particular	O
,	O
are	O
now	O
an	O
estimate	O
rather	O
than	O
the	O
actual	O
measured	O
flow	O
volume	O
.	O
</s>
<s>
VersionCommentv1First	O
implementation	O
,	O
now	O
obsolete	O
,	O
and	O
restricted	O
to	O
IPv4	B-Protocol
(	O
without	O
IP	B-Protocol
mask	I-Protocol
and	O
AS	B-Architecture
Numbers	I-Architecture
)	O
.v2Cisco	O
internal	O
version	O
,	O
never	O
released.v3Cisco	O
internal	O
version	O
,	O
never	O
released.v4Cisco	O
internal	O
version	O
,	O
never	O
released.v5Most	O
common	O
version	O
,	O
available	O
(	O
as	O
of	O
2009	O
)	O
on	O
many	O
routers	B-Protocol
from	O
different	O
brands	O
,	O
but	O
restricted	O
to	O
IPv4	B-Protocol
flows.v6No	O
longer	O
supported	O
by	O
Cisco	O
.	O
</s>
<s>
)	O
.v7Like	O
version	O
5	O
with	O
a	O
source	O
router	B-Protocol
field	O
.	O
</s>
<s>
on	O
Cisco	B-Device
Catalyst	I-Device
switches.v8Several	O
aggregation	O
form	O
,	O
but	O
only	O
for	O
information	O
that	O
is	O
already	O
present	O
in	O
version	O
5	O
recordsv9Template	O
Based	O
,	O
available	O
(	O
as	O
of	O
2009	O
)	O
on	O
some	O
recent	O
routers	B-Protocol
.	O
</s>
<s>
Mostly	O
used	O
to	O
report	O
flows	O
like	O
IPv6	B-Protocol
,	O
MPLS	B-Protocol
,	O
or	O
even	O
plain	O
IPv4	B-Protocol
with	O
BGP	O
nexthop.v10Used	O
for	O
identifying	O
IPFIX	B-Protocol
.	O
</s>
<s>
Although	O
IPFIX	B-Protocol
is	O
heavily	O
based	O
on	O
NetFlow	B-Protocol
,	O
v10	O
does	O
not	O
have	O
anything	O
to	O
do	O
with	O
NetFlow	B-Protocol
.	O
</s>
<s>
NetFlow	B-Protocol
was	O
initially	O
implemented	O
by	O
Cisco	O
,	O
and	O
described	O
in	O
an	O
"	O
informational	O
"	O
document	O
that	O
was	O
not	O
on	O
the	O
standards	O
track	O
:	O
RFC	O
3954	O
Cisco	O
Systems	O
NetFlow	B-Protocol
Services	O
Export	O
Version	O
9	O
.	O
</s>
<s>
The	O
NetFlow	B-Protocol
protocol	O
itself	O
has	O
been	O
superseded	O
by	O
Internet	B-Protocol
Protocol	I-Protocol
Flow	O
Information	O
eXport	O
(	O
IPFIX	B-Protocol
)	O
.	O
</s>
<s>
Based	O
on	O
the	O
NetFlow	B-Protocol
Version	O
9	O
implementation	O
,	O
IPFIX	B-Protocol
is	O
on	O
the	O
IETF	O
standards	O
track	O
with	O
RFC	O
5101	O
(	O
obsoleted	O
by	O
RFC	O
7011	O
)	O
,	O
RFC	O
5102	O
(	O
obsoleted	O
by	O
RFC	O
7012	O
)	O
,	O
etc	O
.	O
</s>
<s>
NetFlow	B-Protocol
may	O
be	O
a	O
prevalent	O
name	O
in	O
the	O
area	O
of	O
flow	O
monitoring	O
,	O
because	O
of	O
Cisco	O
dominant	O
market	O
share	O
in	O
the	O
networking	O
industry	O
.	O
</s>
<s>
NetFlow	B-Protocol
is	O
thought	O
to	O
be	O
a	O
Cisco	O
trademark	O
(	O
even	O
though	O
as	O
of	O
March	O
2012	O
it	O
is	O
not	O
listed	O
in	O
Cisco	O
Trademarks	O
)	O
:	O
</s>
<s>
Also	O
flow-tools	O
collection	O
of	O
software	O
allows	O
to	O
process	O
and	O
manage	O
NetFlow	B-Protocol
exports	O
from	O
Cisco	O
and	O
Juniper	O
routers	B-Protocol
.	O
</s>
<s>
Vendor	O
and	O
type	O
Models	O
NetFlow	B-Protocol
Version	O
Implementation	O
Comments	O
Cisco	O
IOS-XR	O
routers	B-Protocol
CRS	B-Protocol
,	O
ASR9000	B-Protocol
old	O
12000	B-Device
v5	O
,	O
v8	O
,	O
v9	O
Software	O
running	O
on	O
line	O
card	O
CPU	O
Comprehensive	O
support	O
for	O
IPv6	B-Protocol
and	O
MPLS	B-Protocol
Cisco	B-Protocol
IOS	I-Protocol
routers	B-Protocol
10000	O
,	O
7200	O
,	O
old	O
7500	O
v5	O
,	O
v8	O
,	O
v9	O
Software	O
running	O
on	O
Route	O
Processor	O
support	O
for	O
IPv6	B-Protocol
or	O
MPLS	B-Protocol
require	O
recent	O
model	O
and	O
IOS	B-Protocol
Cisco	B-Device
Catalyst	I-Device
switches	O
7600	O
,	O
6500	O
,	O
4500	O
v5	O
,	O
v8	O
,	O
v9	O
Dedicated	O
hardware	O
TCAM	O
,	O
also	O
used	O
for	O
ACLs	O
.	O
</s>
<s>
Support	O
for	O
IPv6	B-Protocol
on	O
high-end	O
models	O
RSP720	O
and	O
Sup720	O
,	O
but	O
at	O
most	O
128K	O
or	O
256K	O
flows	O
per	O
PCF	O
card	O
.	O
</s>
<s>
Cisco	B-Protocol
Nexus	I-Protocol
switches	O
5600	O
,	O
7000	O
,	O
7700	O
v5	O
,	O
v9	O
Dedicated	O
hardware	O
TCAM	O
,	O
also	O
used	O
for	O
ACLs	O
.	O
</s>
<s>
Support	O
IPv4/IPv6/L2	O
.	O
</s>
<s>
MPLS	B-Protocol
not	O
supported	O
Juniper	O
legacy	O
routers	B-Protocol
M-series	B-Protocol
,	O
T-series	B-Protocol
,	O
MX-series	B-Protocol
with	O
DPC	O
v5	O
,	O
v8	O
Software	O
running	O
on	O
Routing	B-Protocol
Engine	O
,	O
called	O
software	O
jflow	O
IPv6	B-Protocol
and	O
MPLS	B-Protocol
not	O
supported	O
Juniper	O
legacy	O
routers	B-Protocol
M-series	B-Protocol
,	O
T-series	B-Protocol
,	O
MX-series	B-Protocol
with	O
DPC	O
v5	O
,	O
v8	O
,	O
v9	O
Software	O
running	O
on	O
service	O
PIC	O
,	O
called	O
hardware	O
jflow	O
or	O
sampled	O
IPv6	B-Protocol
or	O
MPLS	B-Protocol
supported	O
on	O
MS-DPC	O
,	O
MultiService-PIC	O
,	O
AS-PIC2	O
Juniper	O
routers	B-Protocol
MX-series	B-Protocol
with	O
MPC-3D	O
,	O
FPC5	O
for	O
T4000	O
v5	O
,	O
IPFIX	B-Protocol
Hardware	O
(	O
trio	O
chipset	O
)	O
,	O
called	O
inline	O
jflow	O
IPv6	B-Protocol
requires	O
JUNOS	O
11.4R2	O
(	O
back	O
port	O
target	O
)	O
,	O
MPLS	B-Protocol
support	O
unknown	O
,	O
MPC3E	O
excluded	O
until	O
12.3	O
,	O
incorrect	O
start	O
time	O
field	O
causing	O
incorrect	O
data	O
throughput	O
result	O
Nokia	O
routers	B-Protocol
7750SR	O
v5	O
,	O
v8	O
,	O
v9	O
,	O
v10	O
IPFIX	B-Protocol
Software	O
running	O
on	O
Central	O
Processor	O
Module	O
IPv6	B-Protocol
or	O
MPLS	B-Protocol
using	O
IOM3	O
line	O
cards	O
or	O
better	O
Huawei	O
routers	B-Protocol
NE5000E	O
NE40E/X	O
NE80E	O
v5	O
,	O
v9	O
Software	O
running	O
on	O
service	O
cards	O
Support	O
for	O
IPv6	B-Protocol
or	O
MPLS	B-Protocol
is	O
unknown	O
Enterasys	O
Switches	O
S-Serie	O
and	O
N-Serie	O
v5	O
,	O
v9	O
Dedicated	O
hardware	O
IPv6	B-Protocol
support	O
is	O
unknown	O
Flowmon	B-Protocol
Probes	O
Flowmon	B-Protocol
Probe	O
1000	O
,	O
2000	O
,	O
4000	O
,	O
6000	O
,	O
10000	O
,	O
20000	O
,	O
40000	O
,	O
80000	O
,	O
100000	O
v5	O
,	O
v9	O
,	O
IPFIX	B-Protocol
Software	O
or	O
hardware-accelerated	O
Comprehensive	O
support	O
for	O
IPv6	B-Protocol
and	O
MPLS	B-Protocol
,	O
wire-speed	O
Nortel	O
Switches	O
Ethernet	B-Protocol
Routing	B-Protocol
Switch	O
5500	O
Series	O
(	O
ERS5510	O
,	O
5520	O
and	O
5530	O
)	O
and	O
8600	O
(	O
Chassis-based	O
)	O
v5	O
,	O
v9	O
,	O
IPFIX	B-Protocol
Software	O
running	O
on	O
line	O
card	O
CPU	O
Comprehensive	O
support	O
for	O
IPv6	B-Protocol
PC	O
and	O
Servers	O
Linux	B-Application
FreeBSD	B-Operating_System
NetBSD	B-Device
OpenBSD	B-Operating_System
v5	O
,	O
v9	O
,	O
IPFIX	B-Protocol
Software	O
like	O
fprobe	O
,	O
ipt-netflow	O
,	O
pflow	O
,	O
flowd	O
,	O
Netgraph	B-Device
ng_netflow	O
or	O
softflowd	O
IPv6	B-Protocol
support	O
depend	O
on	O
the	O
software	O
used	O
VMware	O
servers	O
vSphere	O
5.x	O
v5	O
,	O
IPFIX	B-Protocol
(	O
>5.1	O
)	O
http://www.vmware.com/files/pdf/techpaper/Whats-New-VMware-vSphere-51-Network-Technical-Whitepaper.pdf	O
Software	O
IPv6	B-Protocol
support	O
is	O
unknown	O
Mikrotik	O
RouterOS	O
RouterOS	O
3.x	O
,	O
4.x	O
,	O
5.x	O
,	O
6.x	O
v1	O
,	O
v5	O
,	O
v9	O
,	O
IPFIX	B-Protocol
(	O
>6.36RC3	O
)	O
Software	O
and	O
Routerboard	O
hardware	O
IPv6	B-Protocol
is	O
supported	O
using	O
v9	O
.	O
</s>
<s>
Currently	O
RouterOS	O
does	O
not	O
include	O
BGP	O
AS	B-Architecture
numbers	I-Architecture
.	O
</s>
<s>
Introduced	O
with	O
the	O
launch	O
of	O
the	O
Cisco	B-Language
ASA	I-Language
5580	O
products	O
,	O
utilizes	O
NetFlow	B-Protocol
v9	O
fields	O
and	O
templates	O
in	O
order	O
to	O
efficiently	O
deliver	O
security	O
telemetry	O
in	O
high	O
performance	O
environments	O
.	O
</s>
<s>
NetFlow	B-Protocol
Security	O
Event	O
Logging	O
scales	O
better	O
than	O
syslog	B-Protocol
while	O
offering	O
the	O
same	O
level	O
of	O
detail	O
and	O
granularity	O
in	O
logged	O
events	O
.	O
</s>
<s>
NetFlow	B-Protocol
collection	O
using	O
standalone	O
NetFlow	B-Protocol
probes	O
is	O
an	O
alternative	O
to	O
flow	O
collection	O
from	O
routers	B-Protocol
and	O
switches	O
.	O
</s>
<s>
This	O
approach	O
can	O
overcome	O
some	O
limitations	O
of	O
router-based	O
NetFlow	B-Protocol
monitoring	O
.	O
</s>
<s>
Historically	O
,	O
NetFlow	B-Protocol
monitoring	O
is	O
easier	O
to	O
implement	O
in	O
a	O
dedicated	O
probe	O
than	O
in	O
a	O
router	B-Protocol
.	O
</s>
<s>
probes	O
will	O
not	O
report	O
separate	O
input	O
and	O
output	O
interface	O
information	O
like	O
a	O
report	O
from	O
a	O
router	B-Protocol
would	O
.	O
</s>
<s>
probes	O
may	O
have	O
problems	O
reporting	O
reliably	O
the	O
NetFlow	B-Protocol
fields	O
related	O
to	O
routing	B-Protocol
,	O
like	O
AS	B-Architecture
Numbers	I-Architecture
or	O
IP	B-Protocol
masks	I-Protocol
,	O
because	O
they	O
can	O
hardly	O
be	O
expected	O
to	O
use	O
exactly	O
the	O
same	O
routing	B-Protocol
information	I-Protocol
as	O
a	O
router	B-Protocol
.	O
</s>
<s>
The	O
easiest	O
way	O
to	O
address	O
the	O
above	O
drawbacks	O
is	O
to	O
use	O
a	O
packet	B-Protocol
capture	I-Protocol
appliance	I-Protocol
inline	O
in	O
front	O
of	O
the	O
router	B-Protocol
and	O
capture	O
all	O
of	O
the	O
NetFlow	B-Protocol
output	O
from	O
the	O
router	B-Protocol
.	O
</s>
<s>
This	O
method	O
allows	O
for	O
storage	O
of	O
large	O
amount	O
of	O
NetFlow	B-Protocol
data	O
(	O
typically	O
many	O
years	O
worth	O
of	O
data	O
)	O
and	O
does	O
not	O
require	O
reconfiguration	O
of	O
the	O
network	O
.	O
</s>
<s>
NetFlow	B-Protocol
collection	O
from	O
dedicated	O
probes	O
is	O
well	O
suited	O
for	O
observation	O
of	O
critical	O
links	O
,	O
whereas	O
NetFlow	B-Protocol
on	O
routers	B-Protocol
provides	O
a	O
Network-wide	O
view	O
of	O
the	O
traffic	O
that	O
can	O
be	O
used	O
for	O
capacity	O
planning	O
,	O
accounting	O
,	O
performance	O
monitoring	O
,	O
and	O
security	O
.	O
</s>
<s>
NetFlow	B-Protocol
was	O
originally	O
a	O
Cisco	O
packet	O
switching	O
technology	O
for	O
Cisco	O
routers	B-Protocol
,	O
implemented	O
in	O
IOS	B-Protocol
11.x	O
around	O
1996	O
.	O
</s>
<s>
Netflow	B-Protocol
was	O
invented	O
by	O
Darren	O
Kerr	O
and	O
Barry	O
Bruin	O
from	O
Cisco	O
(	O
U.S.	O
)	O
.	O
</s>
<s>
The	O
idea	O
was	O
that	O
the	O
first	O
packet	O
of	O
a	O
flow	O
would	O
create	O
a	O
NetFlow	B-Protocol
switching	O
record	O
.	O
</s>
<s>
This	O
is	O
an	O
expensive	O
operation	O
in	O
software	O
implementations	O
,	O
especially	O
the	O
old	O
ones	O
without	O
Forwarding	B-Protocol
information	I-Protocol
base	I-Protocol
.	O
</s>
<s>
The	O
NetFlow	B-Protocol
switching	O
record	O
was	O
actually	O
some	O
kind	O
of	O
route	O
cache	O
record	O
,	O
and	O
old	O
versions	O
of	O
IOS	B-Protocol
still	O
refer	O
to	O
the	O
NetFlow	B-Protocol
cache	O
as	O
ip	B-Protocol
route-cache	O
.	O
</s>
<s>
NetFlow	B-Protocol
switching	O
soon	O
turned	O
out	O
to	O
be	O
unsuitable	O
for	O
big	O
routers	B-Protocol
,	O
especially	O
Internet	O
backbone	O
routers	B-Protocol
,	O
where	O
the	O
number	O
of	O
simultaneous	O
flows	O
was	O
much	O
more	O
important	O
than	O
those	O
on	O
local	O
networks	O
,	O
and	O
where	O
some	O
traffic	O
causes	O
many	O
short-lived	O
flows	O
,	O
like	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
requests	O
(	O
whose	O
source	O
port	O
is	O
random	O
for	O
security	O
reasons	O
)	O
.	O
</s>
<s>
As	O
a	O
switching	O
technology	O
,	O
NetFlow	B-Protocol
was	O
replaced	O
around	O
1995	O
by	O
Cisco	B-Protocol
Express	I-Protocol
Forwarding	I-Protocol
.	O
</s>
<s>
This	O
first	O
appeared	O
on	O
Cisco	B-Device
12000	I-Device
routers	B-Protocol
,	O
and	O
later	O
replaced	O
NetFlow	B-Protocol
switching	O
on	O
advanced	O
IOS	B-Protocol
for	O
the	O
Cisco	O
7200	O
and	O
Cisco	O
7500	O
.	O
</s>
<s>
As	O
of	O
2012	O
,	O
technologies	O
similar	O
to	O
NetFlow	B-Protocol
switching	O
are	O
still	O
in	O
use	O
in	O
most	O
firewalls	O
and	O
software-based	O
IP	B-Protocol
routers	I-Protocol
.	O
</s>
<s>
For	O
instance	O
the	O
conntrack	O
feature	O
of	O
the	O
Netfilter	B-Application
framework	O
used	O
by	O
Linux	B-Application
.	O
</s>
