Cisco 7513 Series, Руководство по установке и обслуживанию оборудования

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Functional
Overview
MAC-Layer
Address
Allocator
All
network
interface connections
@orts
except
serial
ports require unique
MAC-layer address
which
is also
known
as
hardware
address
Typically
the
MAC
address of an interface
is
stored
on
memory
component
that
resides
directly
on
the interface
circuitry
however
the
OIR
feature
requires
different
method
The OIR
feature allows
you
to
remove
an interface
processor
and
replace
it
with another
identically
configured
one
If
the
new
interfaces
match
the interfaces
you removed
the
system
immediately
brings
them on
line In order
to
allow
OIR
an address allocator with
unique
MAC
addresses
is
stored
in
an
EEPROM
device
on
the backplane
Each
address
is
reserved
for
specific slot/port
in
the router
regardless
of
whether
an interface resides
in that
port
The
MAC
addresses are assigned
to
the ports
in
sequence
The
first
address
is
assigned to
port
0/0
and
the
last
address
is
assigned to
port
12/n
where
is
the
maximum
number
of ports on the interface
processor
installed in slot
12
This
address
scheme
allows
you
to
remove interface
processors
and
insert
them
into
other routers without
causing
the
MAC
addresses
to
move around
the
network
or
be
assigned
to
multiple
devices
Note
that if
the
MAC
addresses were stored on each interface
processor
OIR
would
not function
because
you
could
never
replace
one interface with
an identical
one the
MAC
addresses
would
always
be different Also each time
an interface
was
replaced
other devices on the
network would
have
to
update
their
data
structures
with the
new
address
and
if
they did not
do
so quickly
enough
could
cause
the same
MAC
address
to
appear
in
more
than
one
device
at
the same time
Note
Storing
the
MAC
addresses for
every
port
in one central location means the addresses
stay
with the
memory
device on which
they
are stored
If
you replace
the
memory
device the addresses
of
all
ports
will
change to
those
specified
in
the address allocator
on
the
new memory
device
Storing
the
MAC
addresses
in
memory device on the backplane avoids these problems
When
an
interface
is
replaced
with another
identical interface
there
is
no need
for
other devices
in
the
network
to update their
data
structures
and
routing
tables
1-34 Cisco 7513 Hardware
Installation
and Maintenance