<s>
In	O
IP-based	B-Protocol
computer	B-Architecture
networks	I-Architecture
,	O
virtual	B-General_Concept
routing	I-General_Concept
and	I-General_Concept
forwarding	I-General_Concept
(	O
VRF	O
)	O
is	O
a	O
technology	O
that	O
allows	O
multiple	O
instances	O
of	O
a	O
routing	B-Protocol
table	I-Protocol
to	O
co-exist	O
within	O
the	O
same	O
router	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
VRFs	O
are	O
the	O
TCP/IP	O
layer	O
3	O
equivalent	O
of	O
a	O
VLAN	B-General_Concept
.	O
</s>
<s>
Because	O
the	O
routing	O
instances	O
are	O
independent	O
,	O
the	O
same	O
or	O
overlapping	O
IP	B-Protocol
addresses	I-Protocol
can	O
be	O
used	O
without	O
conflicting	O
with	O
each	O
other	O
.	O
</s>
<s>
VRFs	O
were	O
initially	O
introduced	O
in	O
combination	O
with	O
Multiprotocol	B-Protocol
Label	I-Protocol
Switching	I-Protocol
(	O
MPLS	B-Protocol
)	O
,	O
but	O
VRF	O
proved	O
to	O
be	O
so	O
useful	O
that	O
it	O
eventually	O
evolved	O
to	O
live	O
independent	O
of	O
MPLS	B-Protocol
.	O
</s>
<s>
This	O
is	O
the	O
historical	O
explanation	O
of	O
the	O
term	O
VRF	O
Lite	O
:	O
usage	O
of	O
VRFs	O
without	O
MPLS	B-Protocol
.	O
</s>
<s>
In	O
a	O
typical	O
deployment	O
,	O
customer	B-Protocol
edge	I-Protocol
(	O
CE	O
)	O
routers	O
handle	O
local	O
routing	O
in	O
a	O
traditional	O
fashion	O
and	O
disseminate	O
routing	O
information	O
into	O
the	O
provider	B-Protocol
edge	I-Protocol
(	O
PE	O
)	O
where	O
the	O
routing	B-Protocol
tables	I-Protocol
are	O
virtualized	O
.	O
</s>
<s>
The	O
PE	B-Protocol
router	I-Protocol
then	O
encapsulates	O
the	O
traffic	O
,	O
marks	O
it	O
to	O
identify	O
the	O
VRF	O
instance	O
,	O
and	O
transmits	O
it	O
across	O
the	O
provider	O
backbone	O
network	O
to	O
the	O
destination	O
PE	B-Protocol
router	I-Protocol
.	O
</s>
<s>
The	O
destination	O
PE	B-Protocol
router	I-Protocol
then	O
decapsulates	O
the	O
traffic	O
and	O
forwards	O
it	O
to	O
the	O
CE	B-Protocol
router	I-Protocol
at	O
the	O
destination	O
.	O
</s>
<s>
Routes	O
across	O
the	O
provider	O
backbone	O
network	O
are	O
maintained	O
using	O
an	O
interior	B-Protocol
gateway	I-Protocol
protocol	I-Protocol
–	O
typically	O
iBGP	B-Protocol
.	O
</s>
<s>
IBGP	B-Protocol
uses	O
extended	O
community	O
attributes	O
in	O
a	O
common	O
routing	B-Protocol
table	I-Protocol
to	O
differentiate	O
the	O
customers	O
 '	O
routes	O
with	O
overlapping	O
IP	B-Protocol
addresses	I-Protocol
.	O
</s>
<s>
IPVPN	O
is	O
most	O
commonly	O
deployed	O
across	O
an	O
MPLS	B-Protocol
backbone	O
as	O
the	O
inherent	O
labeling	O
of	O
packets	O
in	O
MPLS	B-Protocol
lends	O
itself	O
to	O
the	O
identification	O
of	O
the	O
customer	O
VRF	O
.	O
</s>
<s>
Some	O
IPVPN	O
implementations	O
(	O
notably	O
Nortel	O
's	O
IP-VPN	O
Lite	O
)	O
use	O
a	O
simpler	O
IP-in-IP	B-Protocol
encapsulation	O
over	O
a	O
pure	O
IP	B-Protocol
backbone	O
,	O
eliminating	O
the	O
need	O
to	O
maintain	O
and	O
support	O
an	O
MPLS	B-Protocol
environment	O
.	O
</s>
