<s>
In	O
computer	B-Architecture
networking	I-Architecture
,	O
the	O
default	B-Protocol
route	I-Protocol
is	O
a	O
configuration	O
of	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
that	O
establishes	O
a	O
forwarding	O
rule	O
for	O
packets	B-Protocol
when	O
no	O
specific	O
address	O
of	O
a	O
next-hop	O
host	O
is	O
available	O
from	O
the	O
routing	B-Protocol
table	I-Protocol
or	O
other	O
routing	O
mechanisms	O
.	O
</s>
<s>
The	O
default	B-Protocol
route	I-Protocol
is	O
generally	O
the	O
address	O
of	O
another	O
router	O
,	O
which	O
treats	O
the	O
packet	B-Protocol
the	O
same	O
way	O
:	O
if	O
a	O
route	O
matches	O
,	O
the	O
packet	B-Protocol
is	O
forwarded	O
accordingly	O
,	O
otherwise	O
the	O
packet	B-Protocol
is	O
forwarded	O
to	O
the	O
default	B-Protocol
route	I-Protocol
of	O
that	O
router	O
.	O
</s>
<s>
The	O
route	O
evaluation	O
process	O
in	O
each	O
router	O
uses	O
the	O
longest	B-Protocol
prefix	I-Protocol
match	I-Protocol
method	O
to	O
obtain	O
the	O
most	O
specific	O
route	O
.	O
</s>
<s>
The	O
network	O
with	O
the	O
longest	O
subnet	B-Protocol
mask	I-Protocol
or	O
network	O
prefix	O
that	O
matches	O
the	O
destination	O
IP	B-Protocol
address	I-Protocol
is	O
the	O
next-hop	O
network	O
gateway	O
.	O
</s>
<s>
The	O
process	O
repeats	O
until	O
a	O
packet	B-Protocol
is	O
delivered	O
to	O
the	O
destination	O
host	O
,	O
or	O
earlier	O
along	O
the	O
route	O
,	O
when	O
a	O
router	O
has	O
no	O
default	B-Protocol
route	I-Protocol
available	O
and	O
cannot	O
route	O
the	O
packet	B-Protocol
otherwise	O
.	O
</s>
<s>
In	O
the	O
latter	O
case	O
,	O
the	O
packet	B-Protocol
is	O
dropped	O
and	O
an	O
ICMP	O
Destination	O
Unreachable	O
message	O
may	O
be	O
returned	O
.	O
</s>
<s>
The	O
device	O
to	O
which	O
the	O
default	B-Protocol
route	I-Protocol
points	O
is	O
often	O
called	O
the	O
default	B-Protocol
gateway	I-Protocol
,	O
and	O
it	O
often	O
carries	O
out	O
other	O
functions	O
such	O
as	O
packet	B-Application
filtering	I-Application
,	O
firewalling	B-Application
,	O
or	O
proxy	B-Application
server	I-Application
operations	O
.	O
</s>
<s>
The	O
default	B-Protocol
route	I-Protocol
in	O
Internet	B-Protocol
Protocol	I-Protocol
Version	I-Protocol
4	I-Protocol
(	O
IPv4	B-Protocol
)	O
is	O
designated	O
as	O
the	O
zero	O
address	O
,	O
in	O
CIDR	B-Protocol
notation	I-Protocol
.	O
</s>
<s>
Similarly	O
,	O
in	O
IPv6	B-Protocol
,	O
the	O
default	B-Protocol
route	I-Protocol
is	O
specified	O
by	O
.	O
</s>
<s>
The	O
subnet	B-Protocol
mask	I-Protocol
is	O
specified	O
as	O
,	O
which	O
effectively	O
specifies	O
all	O
networks	O
and	O
is	O
the	O
shortest	O
match	O
possible	O
.	O
</s>
<s>
In	O
the	O
highest-level	O
segment	O
of	O
a	O
network	O
,	O
administrators	O
generally	O
point	O
the	O
default	B-Protocol
route	I-Protocol
for	O
a	O
given	O
host	O
towards	O
the	O
router	O
that	O
has	O
a	O
connection	O
to	O
a	O
network	O
service	O
provider	O
.	O
</s>
<s>
Therefore	O
,	O
packets	B-Protocol
with	O
destinations	O
outside	O
the	O
organization	O
's	O
LAN	B-General_Concept
,	O
typically	O
destinations	O
on	O
the	O
Internet	O
or	O
a	O
wide	O
area	O
network	O
,	O
are	O
forwarded	O
to	O
the	O
router	O
with	O
the	O
connection	O
to	O
that	O
provider	O
.	O
</s>
