<s>
In	O
computer	O
networking	O
,	O
the	O
Hot	B-Protocol
Standby	I-Protocol
Router	I-Protocol
Protocol	I-Protocol
(	O
HSRP	B-Protocol
)	O
is	O
a	O
Cisco	O
proprietary	O
redundancy	O
protocol	O
for	O
establishing	O
a	O
fault-tolerant	B-General_Concept
default	B-Protocol
gateway	I-Protocol
.	O
</s>
<s>
The	O
protocol	O
establishes	O
an	O
association	O
between	O
gateways	B-Application
in	O
order	O
to	O
achieve	O
default	B-Protocol
gateway	I-Protocol
failover	O
if	O
the	O
primary	O
gateway	B-Application
becomes	O
inaccessible	O
.	O
</s>
<s>
HSRP	B-Protocol
gateways	B-Application
send	O
multicast	B-Protocol
hello	O
messages	O
to	O
other	O
gateways	B-Application
to	O
notify	O
them	O
of	O
their	O
priorities	O
(	O
which	O
gateway	B-Application
is	O
preferred	O
)	O
and	O
current	O
status	O
(	O
active	O
or	O
standby	O
)	O
.	O
</s>
<s>
The	O
primary	O
router	O
with	O
the	O
highest	O
configured	O
priority	O
will	O
act	O
as	O
a	O
virtual	O
router	O
with	O
a	O
pre-defined	O
gateway	B-Application
IP	B-Protocol
address	O
and	O
will	O
respond	O
to	O
the	O
ARP	O
or	O
ND	B-Protocol
request	O
from	O
machines	O
connected	O
to	O
the	O
LAN	O
with	O
a	O
virtual	O
MAC	O
address	O
.	O
</s>
<s>
If	O
the	O
primary	O
router	O
should	O
fail	O
,	O
the	O
router	O
with	O
the	O
next-highest	O
priority	O
would	O
take	O
over	O
the	O
gateway	B-Application
IP	B-Protocol
address	O
and	O
answer	O
ARP	O
requests	O
with	O
the	O
same	O
MAC	O
address	O
,	O
thus	O
achieving	O
transparent	O
default	B-Protocol
gateway	I-Protocol
failover	O
.	O
</s>
<s>
HSRP	B-Protocol
is	O
not	O
a	O
routing	B-Protocol
protocol	I-Protocol
as	O
it	O
does	O
not	O
advertise	O
IP	B-Protocol
routes	O
or	O
affect	O
the	O
routing	B-Protocol
table	O
in	O
any	O
way	O
.	O
</s>
<s>
HSRP	B-Protocol
has	O
the	O
ability	O
to	O
trigger	O
a	O
failover	O
if	O
one	O
or	O
more	O
interfaces	O
on	O
the	O
router	O
go	O
down	O
.	O
</s>
<s>
This	O
can	O
be	O
useful	O
for	O
dual	O
branch	O
routers	O
each	O
with	O
a	O
single	O
link	O
back	O
to	O
the	O
gateway	B-Application
.	O
</s>
<s>
If	O
the	O
link	O
of	O
the	O
primary	O
router	O
goes	O
down	O
,	O
the	O
backup	O
router	O
will	O
take	O
over	O
the	O
primary	O
functionality	O
and	O
thus	O
retain	O
connectivity	O
to	O
the	O
gateway	B-Application
.	O
</s>
<s>
It	O
is	O
not	O
compatible	O
with	O
version	O
1	O
HSRP	B-Protocol
.	O
</s>
