<s>
A	O
bypass	B-Device
switch	I-Device
(	O
or	O
bypass	O
TAP	O
)	O
is	O
a	O
hardware	O
device	O
that	O
provides	O
a	O
fail-safe	O
access	O
port	O
for	O
an	O
in-line	O
active	O
security	O
appliance	O
such	O
as	O
an	O
intrusion	O
prevention	O
system	O
(	O
IPS	O
)	O
,	O
next	O
generation	O
firewall	O
(	O
NGFW	O
)	O
,	O
etc	O
.	O
</s>
<s>
The	O
bypass	B-Device
switch	I-Device
or	O
bypass	O
tap	O
removes	O
this	O
point	O
of	O
failure	O
by	O
automatically	O
'	O
switching	O
traffic	O
via	O
bypass	O
mode	O
 '	O
to	O
keep	O
the	O
critical	O
network	O
link	O
up	O
.	O
</s>
<s>
A	O
bypass	B-Device
switch	I-Device
has	O
four	O
ports	O
.	O
</s>
<s>
This	O
connection	O
is	O
fully	O
passive	O
;	O
if	O
the	O
bypass	B-Device
switch	I-Device
itself	O
loses	O
power	O
,	O
traffic	O
continues	O
to	O
flow	O
unimpeded	O
through	O
the	O
link	O
.	O
</s>
<s>
During	O
normal	O
operation	O
,	O
the	O
bypass	B-Device
switch	I-Device
passes	O
all	O
network	O
traffic	O
through	O
the	O
appliance	O
as	O
if	O
it	O
were	O
directly	O
in-line	O
itself	O
.	O
</s>
<s>
But	O
when	O
the	O
in-line	O
appliance	O
loses	O
power	O
,	O
is	O
disconnected	O
,	O
or	O
otherwise	O
fails	O
,	O
the	O
bypass	B-Device
switch	I-Device
passes	O
traffic	O
directly	O
between	O
its	O
network	O
ports	O
,	O
bypassing	O
the	O
appliance	O
,	O
and	O
ensuring	O
that	O
traffic	O
continues	O
to	O
flow	O
on	O
the	O
network	O
link	O
.	O
</s>
<s>
A	O
bypass	B-Device
switch	I-Device
or	O
TAP	O
monitors	O
the	O
health	O
of	O
the	O
active	O
,	O
in-line	O
appliance	O
by	O
sending	O
heartbeats	O
to	O
the	O
in-line	O
security	O
appliance	O
as	O
long	O
as	O
the	O
in	O
band	O
security	O
appliance	O
is	O
on-line	O
,	O
the	O
heartbeat	O
packets	O
will	O
be	O
returned	O
to	O
the	O
switch/TAP	O
,	O
and	O
the	O
link	O
traffic	O
will	O
continue	O
to	O
flow	O
through	O
the	O
in-line	O
security	O
appliance	O
.	O
</s>
<s>
In	O
some	O
products	O
,	O
when	O
the	O
bypass	B-Device
switch	I-Device
shunts	O
traffic	O
around	O
the	O
monitoring	O
appliance	O
,	O
the	O
monitor	O
ports	O
revert	O
to	O
acting	O
like	O
a	O
network	B-Device
tap	I-Device
,	O
mirroring	O
the	O
half-duplex	O
traffic	O
received	O
at	O
the	O
network	O
ports	O
to	O
the	O
monitor	O
ports	O
.	O
</s>
<s>
Multi-segment	O
bypass	B-Device
switches	I-Device
provide	O
a	O
number	O
of	O
independent	O
bypass	B-Device
switches	I-Device
in	O
a	O
single	O
chassis	O
,	O
providing	O
higher	O
density	O
in	O
the	O
equipment	O
rack	O
.	O
</s>
<s>
Using	O
an	O
external	O
bypass	B-Device
switch	I-Device
to	O
connect	O
an	O
in-line	O
appliance	O
such	O
as	O
a	O
NGFW	O
,	O
IPS	O
,	O
or	O
DDoS	O
has	O
several	O
benefits	O
.	O
</s>
<s>
Bypass	B-Device
switches	I-Device
and	O
TAPs	O
add	O
acquisition	O
cost	O
to	O
the	O
monitoring	O
solution	O
,	O
although	O
they	O
may	O
save	O
cost	O
in	O
the	O
long	O
run	O
by	O
increasing	O
network	O
uptime	O
.	O
</s>
<s>
Bypass	B-Device
switches	I-Device
move	O
the	O
single	B-Architecture
point	I-Architecture
of	I-Architecture
failure	I-Architecture
from	O
the	O
in-line	O
monitoring	O
appliance	O
to	O
the	O
bypass	B-Device
switch	I-Device
itself	O
.	O
</s>
<s>
This	O
should	O
be	O
a	O
net	O
gain	O
in	O
reliability	O
,	O
because	O
the	O
bypass	B-Device
switch	I-Device
is	O
a	O
simpler	O
device	O
than	O
the	O
monitoring	O
appliance	O
,	O
and	O
because	O
it	O
is	O
designed	O
for	O
fault-tolerance	O
.	O
</s>
<s>
Nevertheless	O
,	O
reliability	O
is	O
an	O
important	O
criterion	O
when	O
evaluating	O
bypass	B-Device
switch	I-Device
solutions	O
.	O
</s>
<s>
Bypass	B-Device
switches	I-Device
increase	O
network	O
reliability	O
through	O
several	O
mechanisms	O
including	O
passive	O
in-line	O
connections	O
,	O
link	O
detection	O
,	O
and	O
heartbeat	O
packets	O
.	O
</s>
<s>
The	O
two	O
network	O
ports	O
in	O
a	O
bypass	B-Device
switch	I-Device
create	O
a	O
fully	O
passive	O
in-line	O
connection	O
that	O
maintains	O
traffic	O
flow	O
even	O
in	O
the	O
absence	O
of	O
power	O
.	O
</s>
<s>
The	O
bypass	B-Device
switch	I-Device
monitors	O
the	O
status	O
of	O
the	O
links	O
between	O
its	O
monitor	O
ports	O
and	O
the	O
in-line	O
appliance	O
.	O
</s>
<s>
If	O
a	O
link	O
goes	O
down	O
,	O
the	O
bypass	B-Device
switch	I-Device
immediately	O
switches	O
into	O
bypass	O
-	O
mode	O
.	O
</s>
<s>
When	O
the	O
link	O
comes	O
back	O
up	O
again	O
,	O
the	O
bypass	B-Device
switch	I-Device
returns	O
to	O
bypass-off	O
normal	O
.	O
</s>
<s>
Some	O
bypass	B-Device
switches	I-Device
send	O
a	O
heartbeat	O
packet	O
through	O
the	O
monitoring	O
appliance	O
in	O
order	O
to	O
ensure	O
that	O
the	O
appliance	O
is	O
passing	O
traffic	O
.	O
</s>
<s>
If	O
the	O
heartbeat	O
packet	O
does	O
not	O
return	O
to	O
the	O
bypass	B-Device
switch	I-Device
,	O
the	O
appliance	O
is	O
assumed	O
to	O
be	O
down	O
,	O
and	O
the	O
switch	O
goes	O
into	O
bypass-on	O
mode	O
,	O
excluding	O
the	O
appliance	O
from	O
the	O
traffic	O
path	O
.	O
</s>
<s>
The	O
bypass	B-Device
switch	I-Device
continues	O
to	O
transmit	O
heartbeat	O
packets	O
to	O
the	O
appliance	O
,	O
and	O
when	O
they	O
are	O
again	O
returned	O
by	O
the	O
appliance	O
,	O
the	O
bypass	B-Device
switch	I-Device
changes	O
back	O
to	O
bypass-off	O
mode	O
and	O
the	O
appliance	O
resumes	O
receiving	O
traffic	O
....	O
</s>
<s>
Whenever	O
the	O
bypass	B-Device
switch	I-Device
transitions	O
to	O
bypass	O
mode	O
for	O
any	O
reason	O
,	O
the	O
link	O
may	O
be	O
temporarily	O
dropped	O
.	O
</s>
<s>
A	O
good	O
bypass	B-Device
switch	I-Device
reconnects	O
the	O
link	O
in	O
under	O
1	O
second	O
,	O
but	O
the	O
network	O
may	O
take	O
several	O
seconds	O
to	O
re-establish	O
communications	O
on	O
link	O
.	O
</s>
<s>
Bypass	B-Device
switches	I-Device
may	O
be	O
managed	O
through	O
any	O
of	O
several	O
interfaces	O
:	O
a	O
command-line	O
interface	O
(	O
CLI	O
)	O
,	O
a	O
Web	O
browser-based	O
interface	O
,	O
or	O
a	O
platform-based	O
SNMP	B-Protocol
tool	O
.	O
</s>
<s>
Management	O
functions	O
may	O
include	O
configuring	O
an	O
IP	O
address	O
for	O
SNMP	B-Protocol
traps	O
,	O
retrieving	O
RMON	O
statistics	O
,	O
and	O
setting	O
parameters	O
for	O
the	O
heartbeat	O
packet	O
such	O
as	O
packet	O
contents	O
,	O
timing	O
,	O
and	O
retry	O
counts	O
.	O
</s>
