<s>
The	O
diffusing	B-Protocol
update	I-Protocol
algorithm	I-Protocol
(	O
DUAL	O
)	O
is	O
the	O
algorithm	O
used	O
by	O
Cisco	O
's	O
EIGRP	B-Protocol
routing	O
protocol	O
to	O
ensure	O
that	O
a	O
given	O
route	O
is	O
recalculated	O
globally	O
whenever	O
it	O
might	O
cause	O
a	O
routing	O
loop	O
.	O
</s>
<s>
The	O
full	O
name	O
of	O
the	O
algorithm	O
is	O
DUAL	O
finite-state	B-Architecture
machine	I-Architecture
(	O
DUAL	B-Protocol
FSM	I-Protocol
)	O
.	O
</s>
<s>
EIGRP	B-Protocol
is	O
responsible	O
for	O
the	O
routing	O
within	O
an	O
autonomous	B-Architecture
system	I-Architecture
,	O
and	O
DUAL	O
responds	O
to	O
changes	O
in	O
the	O
routing	O
topology	O
and	O
dynamically	O
adjusts	O
the	O
routing	O
tables	O
of	O
the	O
router	O
automatically	O
.	O
</s>
<s>
EIGRP	B-Protocol
uses	O
a	O
feasibility	O
condition	O
to	O
ensure	O
that	O
only	O
loop-free	O
routes	O
are	O
ever	O
selected	O
.	O
</s>
<s>
When	O
no	O
feasible	O
route	O
to	O
a	O
destination	O
is	O
available	O
,	O
the	O
DUAL	B-Protocol
algorithm	I-Protocol
invokes	O
a	O
diffusing	O
computation	O
to	O
ensure	O
that	O
all	O
traces	O
of	O
the	O
problematic	O
route	O
are	O
eliminated	O
from	O
the	O
network	O
.	O
</s>
<s>
At	O
which	O
point	O
the	O
normal	O
Bellman	B-Algorithm
–	I-Algorithm
Ford	I-Algorithm
algorithm	I-Algorithm
is	O
used	O
to	O
recover	O
a	O
new	O
route	O
.	O
</s>
<s>
These	O
tables	O
are	O
created	O
using	O
information	O
exchanged	O
between	O
the	O
EIGRP	B-Protocol
routers	O
.	O
</s>
<s>
In	O
EIGRP	B-Protocol
,	O
the	O
information	O
exchanged	O
includes	O
the	O
routes	O
,	O
the	O
"	O
metric	O
"	O
or	O
cost	O
of	O
each	O
route	O
,	O
and	O
the	O
information	O
required	O
to	O
form	O
a	O
neighbor	O
relationship	O
(	O
such	O
as	O
AS	B-Architecture
number	I-Architecture
,	O
timers	O
,	O
and	O
K	O
values	O
)	O
.	O
</s>
<s>
Topology	O
table	O
contains	O
the	O
metric	O
(	O
cost	O
information	O
)	O
of	O
all	O
routes	O
to	O
any	O
destination	O
within	O
the	O
autonomous	B-Architecture
system	I-Architecture
.	O
</s>
<s>
"	O
FD	O
(	O
Feasible	O
Distance	O
)	O
"	O
:	O
The	O
calculated	O
metric	O
of	O
a	O
route	O
to	O
a	O
destination	O
within	O
the	O
autonomous	B-Architecture
system	I-Architecture
.	O
</s>
