<s>
In	O
computer	B-Architecture
networking	I-Architecture
and	O
telecommunications	O
,	O
route	B-Protocol
flapping	I-Protocol
occurs	O
when	O
a	O
router	B-Protocol
alternately	O
advertises	O
a	O
destination	O
network	O
via	O
one	O
route	O
then	O
another	O
,	O
or	O
as	O
unavailable	O
and	O
then	O
available	O
again	O
,	O
in	O
quick	O
sequence	O
.	O
</s>
<s>
Route	B-Protocol
flapping	I-Protocol
is	O
caused	O
by	O
pathological	O
conditions	O
(	O
hardware	O
errors	O
,	O
software	O
errors	O
,	O
configuration	O
errors	O
,	O
intermittent	O
errors	O
in	O
communications	O
links	O
,	O
unreliable	O
connections	O
,	O
etc	O
.	O
)	O
</s>
<s>
For	O
example	O
,	O
link	B-Protocol
flap	I-Protocol
occurs	O
when	O
an	O
interface	O
on	O
a	O
router	B-Protocol
has	O
a	O
hardware	O
failure	O
that	O
causes	O
the	O
router	B-Protocol
to	O
announce	O
it	O
alternately	O
as	O
"	O
up	O
"	O
and	O
"	O
down	O
"	O
.	O
</s>
<s>
In	O
networks	O
with	O
link-state	B-Protocol
routing	I-Protocol
protocols	I-Protocol
,	O
route	B-Protocol
flapping	I-Protocol
will	O
force	O
frequent	O
recalculation	O
of	O
the	O
topology	O
by	O
all	O
participating	O
routers	B-Protocol
.	O
</s>
<s>
In	O
networks	O
with	O
distance-vector	B-Protocol
routing	I-Protocol
protocols	I-Protocol
,	O
route	B-Protocol
flapping	I-Protocol
can	O
trigger	O
routing	O
updates	O
with	O
every	O
state	O
change	O
.	O
</s>
<s>
In	O
both	O
cases	O
,	O
it	O
prevents	O
the	O
network	O
from	O
converging	B-Protocol
.	O
</s>
<s>
Route	B-Protocol
flapping	I-Protocol
can	O
be	O
contained	O
to	O
a	O
smaller	O
area	O
of	O
the	O
network	O
if	O
route	B-Protocol
aggregation	I-Protocol
is	O
used	O
.	O
</s>
<s>
As	O
an	O
aggregate	O
route	O
will	O
not	O
be	O
withdrawn	O
as	O
long	O
as	O
at	O
least	O
one	O
of	O
the	O
aggregated	O
subnets	O
is	O
still	O
valid	O
,	O
a	O
flapping	O
route	O
that	O
is	O
part	O
of	O
an	O
aggregate	O
will	O
not	O
disturb	O
the	O
routers	B-Protocol
that	O
receive	O
the	O
aggregate	O
.	O
</s>
