<s>
A	O
multicast	B-Protocol
address	I-Protocol
is	O
a	O
logical	O
identifier	O
for	O
a	O
group	O
of	O
hosts	O
in	O
a	O
computer	B-Architecture
network	I-Architecture
that	O
are	O
available	O
to	O
process	O
datagrams	B-Protocol
or	O
frames	O
intended	O
to	O
be	O
multicast	O
for	O
a	O
designated	O
network	B-General_Concept
service	I-General_Concept
.	O
</s>
<s>
Multicast	O
addressing	O
can	O
be	O
used	O
in	O
the	O
link	B-Protocol
layer	I-Protocol
(	O
layer	O
2	O
in	O
the	O
OSI	O
model	O
)	O
,	O
such	O
as	O
Ethernet	O
multicast	O
,	O
and	O
at	O
the	O
internet	B-Protocol
layer	I-Protocol
(	O
layer	O
3	O
for	O
OSI	O
)	O
for	O
Internet	B-Protocol
Protocol	I-Protocol
Version	I-Protocol
4	I-Protocol
(	O
IPv4	B-Protocol
)	O
or	O
Version	O
6	O
(	O
IPv6	B-Protocol
)	O
multicast	O
.	O
</s>
<s>
IPv4	B-Protocol
multicast	O
addresses	O
are	O
defined	O
by	O
the	O
most-significant	O
bit	O
pattern	O
of	O
1110	O
.	O
</s>
<s>
This	O
originates	O
from	O
the	O
classful	B-Protocol
network	I-Protocol
design	O
of	O
the	O
early	O
Internet	O
when	O
this	O
group	O
of	O
addresses	O
was	O
designated	O
as	O
Class	O
D	O
.	O
The	O
CIDR	B-Protocol
notation	I-Protocol
for	O
this	O
group	O
is	O
.	O
</s>
<s>
Addresses	O
in	O
the	O
range	O
of	O
to	O
are	O
individually	O
assigned	O
by	O
IANA	O
and	O
designated	O
for	O
multicasting	O
on	O
the	O
local	O
subnetwork	B-Protocol
only	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
(	O
RIPv2	O
)	O
uses	O
,	O
Open	B-Protocol
Shortest	I-Protocol
Path	I-Protocol
First	I-Protocol
(	O
OSPF	B-Protocol
)	O
uses	O
and	O
,	O
and	O
Multicast	B-Protocol
DNS	I-Protocol
uses	O
.	O
</s>
<s>
Routers	O
must	O
not	O
forward	O
these	O
messages	O
outside	O
the	O
subnet	B-Protocol
from	O
which	O
they	O
originate	O
.	O
</s>
<s>
This	O
block	O
of	O
addresses	O
is	O
used	O
for	O
traffic	O
that	O
must	O
be	O
routed	O
through	O
the	O
public	O
Internet	O
,	O
such	O
as	O
for	O
applications	O
of	O
the	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
using	O
.	O
</s>
<s>
The	O
(	O
IPv4	B-Protocol
)	O
and	O
(	O
IPv6	B-Protocol
)	O
blocks	O
are	O
reserved	O
for	O
use	O
by	O
source-specific	B-Protocol
multicast	I-Protocol
.	O
</s>
<s>
The	O
range	O
was	O
originally	O
assigned	O
by	O
as	O
an	O
experimental	O
,	O
public	O
statically-assigned	O
multicast	B-Protocol
address	I-Protocol
space	O
for	O
publishers	O
and	O
Internet	O
service	O
providers	O
that	O
wished	O
to	O
source	O
content	O
on	O
the	O
Internet	O
.	O
</s>
<s>
The	O
allocation	O
method	O
is	O
termed	O
GLOP	O
addressing	O
and	O
provides	O
implementers	O
a	O
block	O
of	O
255	O
addresses	O
that	O
is	O
determined	O
by	O
their	O
16-bit	O
autonomous	B-Architecture
system	I-Architecture
number	I-Architecture
(	O
ASN	O
)	O
allocation	O
.	O
</s>
<s>
Unfortunately	O
,	O
with	O
only	O
256	O
multicast	O
addresses	O
available	O
to	O
each	O
autonomous	B-Architecture
system	I-Architecture
,	O
GLOP	O
is	O
not	O
adequate	O
for	O
large-scale	O
broadcasters	O
.	O
</s>
<s>
The	O
range	O
is	O
assigned	O
by	O
as	O
a	O
range	O
of	O
global	O
IPv4	B-Protocol
multicast	B-Protocol
address	I-Protocol
space	O
provided	O
to	O
each	O
organization	O
that	O
has	O
or	O
larger	O
globally	O
routed	O
unicast	B-Protocol
address	I-Protocol
space	O
allocated	O
;	O
one	O
multicast	B-Protocol
address	I-Protocol
is	O
reserved	O
per	O
of	O
unicast	B-Protocol
space	O
.	O
</s>
<s>
A	O
resulting	O
advantage	O
over	O
GLOP	O
is	O
that	O
the	O
unicast-prefix	O
mechanism	O
resembles	O
the	O
unicast-prefix	O
capabilities	O
of	O
IPv6	B-Protocol
as	O
defined	O
in	O
.	O
</s>
<s>
Per	O
the	O
RFC	O
,	O
packets	O
destined	O
to	O
administratively	O
scoped	O
IPv4	B-Protocol
multicast	O
addresses	O
do	O
not	O
cross	O
administratively	O
defined	O
organizational	O
boundaries	O
,	O
and	O
administratively	O
scoped	O
IPv4	B-Protocol
multicast	O
addresses	O
are	O
locally	O
assigned	O
and	O
do	O
not	O
have	O
to	O
be	O
globally	O
unique	O
.	O
</s>
<s>
The	O
RFC	O
also	O
discusses	O
structuring	O
the	O
range	O
to	O
be	O
loosely	O
similar	O
to	O
the	O
scoped	O
IPv6	B-Protocol
multicast	I-Protocol
address	O
range	O
described	O
in	O
.	O
</s>
<s>
In	O
support	O
of	O
link-local	O
multicasts	O
which	O
do	O
not	O
use	O
IGMP	B-Protocol
,	O
any	O
IPv4	B-Protocol
multicast	B-Protocol
address	I-Protocol
that	O
falls	O
within	O
the	O
and	O
ranges	O
will	O
be	O
broadcast	B-Operating_System
to	O
all	O
ports	O
on	O
many	O
Ethernet	O
switches	O
,	O
even	O
if	O
IGMP	B-Protocol
snooping	I-Protocol
is	O
enabled	O
,	O
so	O
addresses	O
within	O
these	O
ranges	O
should	O
be	O
avoided	O
on	O
Ethernet	O
networks	O
where	O
the	O
functionality	O
of	O
IGMP	B-Protocol
snooping	I-Protocol
is	O
desired	O
.	O
</s>
<s>
The	O
following	O
table	O
is	O
a	O
list	O
of	O
notable	O
well-known	O
IPv4	B-Protocol
addresses	O
that	O
are	O
reserved	O
for	O
IP	B-Protocol
multicasting	I-Protocol
and	O
that	O
are	O
registered	O
with	O
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
.	O
</s>
<s>
IP	B-Protocol
multicast	I-Protocol
addressDescriptionRoutable224.0.0.0Base	O
address	O
(	O
reserved	O
)	O
224.0.0.1The	O
All	O
Hosts	O
multicast	O
group	O
addresses	O
all	O
hosts	O
on	O
the	O
same	O
network	O
segment.224.0.0.2The	O
All	O
Routers	O
multicast	O
group	O
addresses	O
all	O
routers	O
on	O
the	O
same	O
network	O
segment.224.0.0.4This	O
address	O
is	O
used	O
in	O
the	O
Distance	B-Protocol
Vector	I-Protocol
Multicast	I-Protocol
Routing	I-Protocol
Protocol	I-Protocol
(	O
DVMRP	B-Protocol
)	O
to	O
address	O
multicast	O
routers.224.0.0.5The	O
Open	B-Protocol
Shortest	I-Protocol
Path	I-Protocol
First	I-Protocol
(	O
OSPF	B-Protocol
)	O
All	O
OSPF	B-Protocol
Routers	O
address	O
is	O
used	O
to	O
send	O
Hello	O
packets	O
to	O
all	O
OSPF	B-Protocol
routers	O
on	O
a	O
network	O
segment.224.0.0.6The	O
OSPF	B-Protocol
All	O
Designated	O
Routers	O
(	O
DR	O
)	O
address	O
is	O
used	O
to	O
send	O
OSPF	B-Protocol
routing	O
information	O
to	O
designated	O
routers	O
on	O
a	O
network	O
segment.224.0.0.9The	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
(	O
RIP	B-Protocol
)	O
version	O
2	O
group	O
address	O
is	O
used	O
to	O
send	O
routing	O
information	O
to	O
all	O
RIP2-aware	O
routers	O
on	O
a	O
network	O
segment.224.0.0.10The	O
Enhanced	B-Protocol
Interior	I-Protocol
Gateway	I-Protocol
Routing	I-Protocol
Protocol	I-Protocol
(	O
EIGRP	B-Protocol
)	O
group	O
address	O
is	O
used	O
to	O
send	O
routing	O
information	O
to	O
all	O
EIGRP	B-Protocol
routers	O
on	O
a	O
network	O
segment.224.0.0.13Protocol	O
Independent	O
Multicast	O
(	O
PIM	B-Protocol
)	O
Version	O
2224.0.0.18Virtual	O
Router	O
Redundancy	O
Protocol	O
(	O
VRRP	B-Protocol
)	O
224.0.0.19	O
–	O
21IS-IS	O
over	O
IP224.0.0.22Internet	O
Group	O
Management	O
Protocol	O
(	O
IGMP	B-Protocol
)	O
version	O
3	O
Section	O
4.2.14224.0.0.102Hot	O
Standby	O
Router	O
Protocol	O
version	O
2	O
(	O
HSRPv2	O
)	O
/	O
Gateway	B-Protocol
Load	I-Protocol
Balancing	I-Protocol
Protocol	I-Protocol
(	O
GLBP	B-Protocol
)	O
224.0.0.107	O
Precision	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
PTP	O
)	O
version	O
2	O
peer	O
delay	O
measurement	O
messaging224.0.0.251Multicast	O
DNS	O
(	O
mDNS	B-Protocol
)	O
address224.0.0.252Link-local	O
Multicast	O
Name	O
Resolution	O
(	O
LLMNR	B-Protocol
)	O
address224.0.0.253Teredo	O
tunneling	O
client	O
discovery	O
address	O
item	O
2.17224.0.1.1Network	O
Time	O
Protocol	O
clients	O
listen	O
on	O
this	O
address	O
for	O
protocol	O
messages	O
when	O
operating	O
in	O
multicast	O
mode.224.0.1.22Service	O
Location	O
Protocol	O
version	O
1	O
general224.0.1.35Service	O
Location	O
Protocol	O
version	O
1	O
directory	O
agent224.0.1.39The	O
Cisco	O
multicast	O
router	O
AUTO-RP-ANNOUNCE	O
address	O
is	O
used	O
by	O
RP	O
mapping	O
agents	O
to	O
listen	O
for	O
candidate	O
announcements.224.0.1.40The	O
Cisco	O
multicast	O
router	O
AUTO-RP-DISCOVERY	O
address	O
is	O
the	O
destination	O
address	O
for	O
messages	O
from	O
the	O
RP	O
mapping	O
agent	O
to	O
discover	O
candidates.224.0.1.41H.323	O
Gatekeeper	O
discovery	O
address224.0.1.129	O
–	O
132Precision	O
Time	O
Protocol	O
(	O
PTP	O
)	O
version	O
1	O
messages	O
(	O
Sync	O
,	O
Announce	O
,	O
etc	O
.	O
)	O
</s>
<s>
Multicast	O
addresses	O
in	O
IPv6	B-Protocol
use	O
the	O
prefix	O
.	O
</s>
<s>
The	O
general	O
format	O
of	O
the	O
IPv6	B-Protocol
multicast	I-Protocol
address	O
is	O
described	O
by	O
RFC	O
4291	O
:	O
</s>
<s>
Based	O
on	O
the	O
value	O
of	O
the	O
flag	O
bits	O
,	O
IPv6	B-Protocol
multicast	I-Protocol
addresses	O
can	O
be	O
Unicast-Prefix-based	O
Multicast	O
Addresses	O
,	O
Source-Specific	B-Protocol
Multicast	I-Protocol
Addresses	O
(	O
both	O
types	O
introduced	O
by	O
RFC	O
3306	O
,	O
updated	O
by	O
RFC	O
7371	O
)	O
,	O
or	O
Embedded	O
RP	O
IPv6	B-Protocol
Multicast	I-Protocol
Addresses	O
(	O
introduced	O
by	O
RFC	O
3956	O
,	O
updated	O
by	O
RFC	O
7371	O
)	O
.	O
</s>
<s>
Similar	O
to	O
a	O
unicast	B-Protocol
address	I-Protocol
,	O
the	O
prefix	O
of	O
an	O
IPv6	B-Protocol
multicast	B-Protocol
address	I-Protocol
specifies	O
its	O
scope	O
,	O
however	O
,	O
the	O
set	O
of	O
possible	O
scopes	O
for	O
a	O
multicast	B-Protocol
address	I-Protocol
is	O
different	O
.	O
</s>
<s>
+Multicast	O
address	O
scopeIPv6	O
addressx	O
is	O
a	O
place	O
holder	O
indicating	O
that	O
the	O
value	O
of	O
the	O
flags	O
field	O
is	O
unimportant	O
in	O
the	O
current	O
discussion.IPv4	O
equivalent	O
section	O
8.ScopePurposeReservedInterface-localPackets	O
with	O
this	O
destination	O
address	O
may	O
not	O
be	O
sent	O
over	O
any	O
network	O
link	O
,	O
but	O
must	O
remain	O
within	O
the	O
current	O
node	O
;	O
this	O
is	O
the	O
multicast	O
equivalent	O
of	O
the	O
unicast	B-Protocol
loopback	O
address.Link-localPackets	O
with	O
this	O
destination	O
address	O
may	O
not	O
be	O
routed	O
anywhere.Realm-Local	O
scopeLocal	O
multicast	O
particular	O
to	O
a	O
network	O
technologyAdmin-localThe	O
smallest	O
scope	O
that	O
must	O
be	O
administratively	O
configured.Site-localRestricted	O
to	O
the	O
local	O
physical	O
network.Organization-localRestricted	O
to	O
networks	O
used	O
by	O
the	O
organization	O
administering	O
the	O
local	O
network	O
.	O
</s>
<s>
(	O
For	O
example	O
,	O
these	O
addresses	O
might	O
be	O
used	O
over	O
VPNs	B-Application
;	O
when	O
packets	O
for	O
this	O
group	O
are	O
routed	O
over	O
the	O
public	O
internet	O
(	O
where	O
these	O
addresses	O
are	O
not	O
valid	O
)	O
,	O
they	O
would	O
have	O
to	O
be	O
encapsulated	O
in	O
some	O
other	O
protocol	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
refers	O
to	O
all	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
NTP	O
)	O
servers	O
on	O
the	O
local	O
network	O
segment	O
,	O
then	O
refers	O
to	O
all	O
NTP	B-Protocol
servers	I-Protocol
in	O
an	O
organization	O
's	O
networks	O
.	O
</s>
<s>
The	O
group	O
ID	O
field	O
may	O
be	O
further	O
divided	O
for	O
special	O
multicast	B-Protocol
address	I-Protocol
types	O
.	O
</s>
<s>
The	O
following	O
table	O
is	O
a	O
list	O
notable	O
IPv6	B-Protocol
multicast	I-Protocol
addresses	O
that	O
are	O
registered	O
with	O
IANA	O
.	O
</s>
<s>
To	O
be	O
included	O
in	O
some	O
of	O
the	O
below	O
multicast	O
groups	O
a	O
client	O
must	O
send	O
a	O
Multicast	B-Protocol
Listener	I-Protocol
Discovery	I-Protocol
(	O
MLD	O
)	O
,	O
a	O
component	O
of	O
ICMPv6	B-Protocol
suite	O
,	O
to	O
join	O
that	O
group	O
.	O
</s>
<s>
For	O
example	O
,	O
to	O
listen	O
to	O
ff02::1:ff28:9c5a	O
,	O
a	O
client	O
must	O
send	O
a	O
MLD	O
report	O
to	O
the	O
router	O
,	O
containing	O
the	O
multicast	B-Protocol
address	I-Protocol
,	O
to	O
indicate	O
that	O
it	O
wants	O
to	O
listen	O
to	O
that	O
group	O
.	O
</s>
<s>
Address	O
Description	O
All	O
nodes	O
on	O
the	O
local	O
network	O
segment	O
All	O
routers	O
on	O
the	O
local	O
network	O
segment	O
OSPFv3	B-Protocol
All	O
SPF	O
routers	O
OSPFv3	B-Protocol
All	O
DR	O
routers	O
IS-IS	B-Protocol
for	O
IPv6	B-Protocol
routers	O
RIP	B-Protocol
routers	O
EIGRP	B-Protocol
routers	O
PIM	B-Protocol
routers	O
Virtual	B-Protocol
Router	I-Protocol
Redundancy	I-Protocol
Protocol	I-Protocol
(	O
VRRP	B-Protocol
)	O
version	O
3	O
MLDv2	B-Protocol
reports	O
All	O
DHCPv6	B-Protocol
servers	O
and	O
relay	O
agents	O
on	O
the	O
local	O
network	O
segment	O
All	O
LLMNR	B-Protocol
hosts	O
on	O
the	O
local	O
network	O
segment	O
All	O
DHCPv6	B-Protocol
servers	O
on	O
the	O
local	O
network	O
site	O
Simple	B-Protocol
Service	I-Protocol
Discovery	I-Protocol
Protocol	I-Protocol
Multicast	B-Protocol
DNS	I-Protocol
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
Network	B-Operating_System
Information	I-Operating_System
Service	I-Operating_System
Precision	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
PTP	O
)	O
version	O
2	O
messages	O
(	O
Sync	O
,	O
Announce	O
,	O
etc	O
.	O
)	O
</s>
<s>
While	O
frames	O
with	O
ones	O
in	O
all	O
bits	O
of	O
the	O
destination	O
address	O
(	O
)	O
are	O
sometimes	O
referred	O
to	O
as	O
broadcasts	B-Operating_System
,	O
Ethernet	O
generally	O
does	O
not	O
distinguish	O
between	O
multicast	O
and	O
broadcast	B-Operating_System
frames	O
.	O
</s>
<s>
Of	O
these	O
,	O
the	O
MAC	O
group	O
addresses	O
in	O
the	O
range	O
of	O
to	O
are	O
not	O
forwarded	O
by	O
802.1D-conformant	O
MAC	B-Protocol
bridges	I-Protocol
.	O
</s>
