Multicast address 41383 225785785 2008-07-15T11:44:16Z 58.20.71.63 /* IPv4 multicast addresses */ In [[computer network]]ing a '''multicast address''' is an identifier for a group of [[Server (computing)|host]]s that have joined a [[multicast]] group. == IPv4 multicast addresses == Within [[Internet Protocol|IPv4]] it is historically known as a '''class D''' address, a type of [[IP address]]. It ranges from 224.0.0.0 to 239.255.255.255, or, equivalently, 224.0.0.0/4 (see [[Classless Inter-Domain Routing]]). Address assignments from within this range are specified in the [[internet engineering task force|IETF]] 'best current practice' [ftp://ftp.isi.edu/in-notes/bcp/bcp51.txt document] also known as RFC 3171. The 224.0.0.0 to 224.0.0.255 range is assigned for multicasting on the local [[Local area network|LAN]] only. Well known examples are [[Routing Information Protocol|RIPv2]] which uses 224.0.0.9 and [[Open Shortest Path First|OSPF]] which uses the 224.0.0.5 address. The following table is a partial list of well-known Class D addresses that are reserved for IP multicasting and registered with the [[Internet Assigned Numbers Authority]] (IANA). {| class="wikitable" |- !IP multicast address !Description |- |224.0.0.0 |Base address (reserved) |- |224.0.0.1 |The All Hosts multicast group that contains all systems on the same network segment |- |224.0.0.2 |The All Routers multicast group that contains all routers on the same network segment |- |224.0.0.5 |The Open Shortest Path First (OSPF) AllSPFRouters address. Used to send Hello packets to all OSPF routers on a network segment |- |224.0.0.6 |The OSPF AllDRouters address. Used to send OSPF routing information to OSPF designated routers on a network segment |- |224.0.0.9 |The RIP Version 2 group address. Used to send RIP routing information to all RIP v2 routers on a network segment |- |224.0.0.10 |EIGRP group address. Used to send EIGRP routing information to all EIGRP routers on a network segment |- |224.0.0.18 |[[Virtual Router Redundancy Protocol]] |- |224.0.0.22 |IGMP Version 3 ([[Internet Group Management Protocol]]) |- |224.0.0.102 |[[Hot Standby Router Protocol]] Version 2 |- |224.0.1.41 |[[H.323 Gatekeeper]] discovery address |} For a full and current listing of additional IP addresses that are reserved for multicasting, see the [http://www.iana.org/assignments/multicast-addresses Internet Multicast Addresses Web site]. The 233.0.0.0/8 range has been assigned by RFC 2770 as public multicast address space that is aligned along [[autonomous system (Internet)|autonomous system]] number allocations. Each byte of the AS number corresponds to the second and third [[octet (computing)|octet]]s of the multicast address. The 239.0.0.0/8 range has been assigned by RFC 2365 as a locally administered address space with local or organizational scope. For advice on choosing multicast addresses for use in your application, see [http://www.29west.com/docs/THPM/multicast-address-assignment.html this page on multicast address assignment]. == IPv6 multicast addresses == Multicast addresses in [[IPv6]] all have the prefix ff00::/8. Address assignments from within this range are specified in RFC 2373. Bits 8 to 11 of the address (i.e., the third hexadecimal digit) are a set of flags, of which only the fourth is currently defined: 0 indicates an address permanently assigned by the [[Internet Assigned Numbers Authority|IANA]], and 1 indicates a non-permanently assigned or "transient" address. (In the addresses given below, an "x" indicates that the value of the digit in that position is unimportant in the current discussion.) Similar to [[unicast]] addresses, IPv6 multicast addresses have different scopes depending on their prefix, though the range of possible scopes is different. The scope is indicated by bits 12 to 15: *ffx0::/16 and ff0f::/16 are reserved. *ffx1::/16 is interface-local, meaning packets with this destination address may not be sent over any network link, but must remain within the current node; this is the multicast equivalent of the unicast [[loopback address]]. *ffx2::/16 is link-local, meaning packets with this destination address may not be routed anywhere. *ffx4::/16 is admin-local, i.e. "the smallest scope that must be administratively configured". *ffx5::/16 is site-local, i.e. restricted to the local physical network. *ffx8::/16 is organization-local, i.e. restricted to networks used by the organization administering the local network. (For example, these addresses might be used over [[VPN]]s; when packets for this group are routed over the public internet (where these addresses are not valid), they would have to be encapsulated in some other protocol.) *ffxe::/16 is global scope, i.e. eligible to be routed over the public internet. *Other scopes are unassigned. These scopes are described in RFC 4291. The "meaning" of a multicast address is unaffected by its scope; for example, if ff02::43 refers to all [[Network Time Protocol|NTP]] servers on the local network segment, then ff08::43 refers to all NTP servers in an organization's networks. The following table is a partial list of well-known IPv6 multicast addresses that are registered with the [[Internet Assigned Numbers Authority]] (IANA). {| class="wikitable" ! Address ! Description |- | ff02::1 | All nodes on the local network segment (equivalent to the IPv4 link-local broadcast address, 169.254.255.255) |- | ff02::2 | All routers on the local network segment |- | ff05::1 | All nodes on the local network site (roughly equivalent to the IPv4 local broadcast addresses 10.255.255.255 and 192.168.255.255) |- | ff0x::fb | [[Zeroconf#Multicast_DNS_.28mDNS.29_and_DNS_Service_Discovery_.28DNS-SD.29|Multicast DNS]] |- | ff0x::108 | [[Network Information Service]] |- | ff0x::114 | Used for experiments |- | ff05::1:3 | All DHCP servers on the local network site (defined in RFC 3315) |} For a full and current listing of additional addresses that are allocated for multicasting, see the [http://www.iana.org/assignments/ipv6-multicast-addresses Internet Protocol Version 6 Multicast Addresses web site]. == Ethernet multicast addresses == Some well known [[Ethernet]] multicast addresses: {| class="wikitable" |- !Ethernet multicast address !Type Field !Usage |- |01-00-0C-CC-CC-CC |0x0802 |[[Cisco Discovery Protocol|CDP]] (Cisco Discovery Protocol), VTP (Virtual Trunking Protocol) |- |01-00-0C-CC-CC-CD |0x0802 |Cisco Shared Spanning Tree Protocol Address |- |01-80-C2-00-00-00 |0x0802 |Spanning Tree Protocol (for bridges) [[IEEE 802.1D]] |- |01-00-5E-xx-xx-xx |0x0800 |IPv4 [[Internet Group Management Protocol|IGMP]] Multicast Address |- |33-33-00-00-00-00 |0x86DD |IPv6 Neighbor Discovery |- |33-33-xx-xx-xx-xx |0x86DD |IPv6 Multicast Address (RFC3307) |} Complete list: http://www.cavebear.com/archive/cavebear/Ethernet/multicast.html == See also == *[[Broadcast address]] [[Category:Network addressing]]