Multicast Addressing

The Internet Assigned Number Authority (IANA) assigned IP Class D space for multicast addressing – 224.0.0.0/4

This includes the range 224.0.0.0 to 239.255.255.255

Address Range	Description
224.0.0.0 – 224.0.0.255	Local Network Control
224.0.1.0 – 224.0.1.255	Internetwork Control
224.0.2.0 – 224.0.255.255	Ad-hoc 1
224.1.0.0 – 224.1.255.255	Reserved
224.2.0.0 – 224.2.255.255	SDP/SAP
224.3.0.0 – 224.4.255.255	Ad-hoc 2
224.5.0.0 – 224.255.255.255	Reserved
225.5.0.0 – 231.255.255.255	Reserved
232.0.0.0 – 232.255.255.255	Source Specific Multicast
233.0.0.0 – 233.251.255.255	GLOP
233.252.0.0 – 233.255.255.255	Ad hoc 3
234.0.0.0 – 238.255.255.255	Reserved
239.0.0.0 – 239.255.255.255	Administratively Scoped

Local Network Control (224.0.0.0/24)

Addresses in this range are considered not to be forwarded out of a broadcast domain. They are used for protocol control traffic such as all hosts in the subnet, 224.0.0.1, all routers in the subnet, 224.0.0.2, and all PIM routers, 224.0.0.13

Internetwork Control (224.0.1.0/24)

Addresses in the internetwork control block may be forwarded across broadcast domains, and even across the internet. Examples of protocols that may use the internetwork control range are NTP, 224.0.1.1, Cisco RP Announce, 224.0.1.39, and Cisco RP Discovery, 224.0.1.40

Source Specific Multicast (232.0.0.0/8)

The 232.0.0.0/8 range is used by SSM. Source Specific Multicast is an extension to PIM as part of RFC 4607. SSM will forward traffic to receivers from only multicast sources that the receivers that have explicitly requested the multicast source.

GLOP (233.0.0.0/8)

Addresses in the GLOP are scoped statically assigned addresses. They are made for domains with a 16-bit AS number by mapping the domains AS number that is expressed in octets as X and Y into the middle two octets of the GLOP block (233.X.Y.0/24)

Domains with 32 bit numbers can utilise space in Ad Hoc 3 or utilise IPv6 multicast addressing.

Administratively Scoped Block (239.0.0.0/8)

These addresses are specified in RFC2365 and are limited to a local group or organisation. The addresses are similar to reserved IP unicast ranges such as 10.0.0.0/8 and 192.168.0.0/16. Network administrators can utilise this range as they please without worry that they will conflict with another organisation on the internet. Even though SSM has been assigned 232.0.0.0/8 it is not uncommon to see it utilise 239.0.0.0/8

Well Known Multicast Addresses

Multicast Address	Description
224.0.0.1	All hosts in subnet
224.0.0.2	All routers in subnet
224.0.0.5	All OSPF routers
224.0.0.6	All OSPF DRs
224.0.0.9	All RIPv2 Routers
224.0.0.10	All EIGRP Routers
224.0.0.13	All PIM Routers
224.0.0.18	VRRP
224.0.0.22	IGMPv3
224.0.0.102	HSRPv2 and GLBP
224.0.1.1	NTP
224.0.1.39	Cisco RP Announce (Auto RP)
224.0.1.40	Cisco RP Discovery (Auto RP)