Modbus
Cellular
Gateway
Index
skipping
is
used
to
reserve
slots
for
new
function
insertion,
when
required.
276
5.7
Redundancy
In
engineering,
redundancy
is
the
duplication
of
critical
components
or
functions
of
a
system
with
the
intention
of
increasing
reliability
of
the
system,
usually
in
the
form
of
a
backup
or
fail
‐
safe.
In
an
IP
networking,
the
access
gateway
is
the
critical
part
of
the
networking
system.
Redundant
gateway
plays
the
backup
one
of
the
master
gateway
and
it
will
take
over
the
data
transmitting
job
once
it
finds
the
master
gateway
failed.
AMIT
security
gateway
can
serve
as
the
redundant
gateway
of
core
router
in
the
enterprise
by
using
the
Virtual
Router
Redundancy
Protocol
(VRRP).
5.7.1
VRRP
The
Virtual
Router
Redundancy
Protocol
(VRRP)
is
a
computer
networking
protocol
providing
device
redundancy.
It
allows
a
backup
router
or
switch
to
automatically
take
over
if
the
primary
(master)
router
or
switch
fails.
This
increases
the
availability
and
reliability
of
routing
paths
via
automatic
default
gateway
selections
on
an
IP
network.
The
protocol
achieves
this
by
creation
of
virtual
routers,
which
are
an
abstract
representation
of
multiple
routers,
i.e.
master
and
backup
routers,
acting
as
a
group.
The
default
gateway
of
a
participating
host
is
assigned
to
the
virtual
router
instead
of
a
physical
router.
If
the
physical
router
that
is
routing
packets
on
behalf
of
the
virtual
router
fails,
another
physical
router
is
selected
to
automatically
replace
it.
The
physical
router
that
is
forwarding
packets
at
any
given
time
is
called
the
master
router.
In
"VRRP"
page,
there
is
only
one
configuration
window
for
Redundancy
function.
A
group
of
physical
VRRP
gateways
combined
together
to
play
a
virtual
server
with
one
unique
virtual
server
ID
and
one
unique
virtual
server
IP
address.
But
these
VRRP
gateways
have
their
own
priority
values
to
serve
as
the
sequence
for
backing
up
the
master
gateway.
VRRP
Configuration
Check
the
"Enable"
box
to
activate
the
VRRP
function
for
the
gateway.
The
gateway
with
VRRP
