<s>
Blackhole	O
DNS	B-Protocol
servers	O
are	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
servers	O
that	O
return	O
a	O
"	O
nonexistent	O
address	O
"	O
answer	O
to	O
reverse	B-Protocol
DNS	I-Protocol
lookups	I-Protocol
for	O
addresses	O
reserved	B-Protocol
for	O
private	O
use	O
.	O
</s>
<s>
There	O
are	O
several	O
ranges	O
of	O
network	O
addresses	O
reserved	B-Protocol
for	O
use	O
on	O
private	B-Protocol
networks	I-Protocol
in	O
IPv4	B-Protocol
:	O
</s>
<s>
To	O
deal	O
with	O
this	O
problem	O
,	O
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
has	O
set	O
up	O
three	O
special	O
DNS	B-Protocol
servers	O
called	O
"	O
blackhole	B-Protocol
servers	I-Protocol
"	O
.	O
</s>
<s>
Currently	O
the	O
blackhole	B-Protocol
servers	I-Protocol
are	O
:	O
</s>
<s>
These	O
servers	O
are	O
registered	O
in	O
the	O
DNS	B-Protocol
directory	O
as	O
the	O
authoritative	O
servers	O
for	O
the	O
reverse	O
lookup	O
zone	O
of	O
the	O
,	O
and	O
addresses	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
answer	O
returned	O
is	O
also	O
allowed	O
to	O
be	O
cached	O
by	O
recursive	O
DNS	B-Protocol
servers	O
.	O
</s>
<s>
According	O
to	O
IANA	O
,	O
"	O
the	O
blackhole	B-Protocol
servers	I-Protocol
generally	O
answer	O
thousands	O
of	O
queries	O
per	O
second	O
"	O
.	O
</s>
<s>
Because	O
the	O
load	O
on	O
the	O
IANA	O
blackhole	B-Protocol
servers	I-Protocol
became	O
very	O
high	O
,	O
an	O
alternative	O
service	O
,	O
AS112	O
,	O
has	O
been	O
created	O
,	O
mostly	O
run	O
by	O
volunteer	O
operators	O
.	O
</s>
<s>
The	O
AS112	O
project	O
is	O
a	O
group	O
of	O
volunteer	O
name	O
server	O
operators	O
joined	O
in	O
an	O
autonomous	B-Architecture
system	I-Architecture
.	O
</s>
<s>
They	O
run	O
anycasted	O
instances	O
of	O
the	O
name	O
servers	O
that	O
answer	O
reverse	B-Protocol
DNS	I-Protocol
lookups	I-Protocol
for	O
private	B-Protocol
network	I-Protocol
and	O
link-local	B-Protocol
addresses	O
sent	O
to	O
the	O
public	O
Internet	O
.	O
</s>
<s>
Providing	O
negative	O
answers	O
reduces	O
the	O
load	O
on	O
the	O
public	O
DNS	B-Protocol
infrastructure	O
.	O
</s>
<s>
Before	O
2001	O
,	O
the	O
in-addr.arpa	B-Protocol
zones	O
for	O
the	O
private	B-Protocol
networks	I-Protocol
were	O
delegated	O
to	O
a	O
single	O
instance	O
of	O
name	O
servers	O
,	O
blackhole-1.iana.org	O
and	O
blackhole-2.iana.org,	O
called	O
the	O
blackhole	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
The	O
IANA-run	O
servers	O
were	O
under	O
increasing	O
load	O
from	O
improperly-configured	O
NAT	O
networks	O
,	O
leaking	O
out	O
reverse	B-Protocol
DNS	I-Protocol
queries	O
,	O
also	O
causing	O
unnecessary	O
load	O
on	O
the	O
root	B-Application
servers	I-Application
.	O
</s>
<s>
The	O
decision	O
was	O
made	O
by	O
a	O
small	O
subset	O
of	O
root	B-Application
server	I-Application
operators	O
to	O
run	O
the	O
reverse	O
delegations	O
;	O
each	O
announcing	O
the	O
network	O
using	O
the	O
autonomous	B-Architecture
system	I-Architecture
number	I-Architecture
of	O
112	O
.	O
</s>
<s>
For	O
the	O
,	O
and	O
private	B-Protocol
networks	I-Protocol
:	O
</s>
<s>
For	O
the	O
link-local	B-Protocol
addresses	O
:	O
</s>
