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Multicast Addressing
IP Multicast Group Addresses
- 224.0.0.0–239.255.255.255
- Class “D” Address Space
- High order bits of 1st Octet = “1110”
- TTL value ~may~ define scope and limits distribution
- IP multicast packet must have TTL > interface TTL or it is discarded
- values are: 0=host, 1=network, 32=same site, 64=same region, 128=same continent, 255=unrestricted
- No longer recommended as a reliable scoping mechanism
Notes:
IANA Reserved Addresses
IANA is the responsible Authority for the assignment of reserved class D addresses. Other interesting reserved addresses are:
224.0.0.2 - PIMv1 (ALL-ROUTERS - due to transport in IGMPv1)
224.0.0.5 - OSPF ALL ROUTERS (RFC1583)
224.0.0.6 - OSPF DESIGNATED ROUTERS (RFC1583)
224.0.0.9 - RIP2 Routers
224.0.0.13 - PIMv2
224.0.1.39 - CISCO-RP-ANNOUNCE (Auto-RP)
224.0.1.40 - CISCO-RP-DISCOVERY (Auto-RP)
“ftp://ftp.isi.edu/in-notes/iana/assignments/multicast-addresses” is the authoritative source for reserved multicast addresses.
Additional Information
"Administratively Scoped IP Multicast", June 1997, has a good discussion on scoped addresses. This document is available at:
“draft-ietf-mboned-admin-ip-space-03.txt”