Administratively scoped multicast address block or Limited scope addresses

The administratively scoped IPv4 multicast address space (or Limited scope addresses) is defined as 239.0.0.0/8. That means the administratively scoped IPv4 multicast address space range is between 239.0.0.0 to 239.255.255.255. Administrative scoped IPv4 multicast address can be compared similar to RFC 1918 private IPv4 unicast addresses. Administratively scoped IPv4 multicast address are defined in RFC 2365.

Multicast IPv4 packets addressed to administratively scoped multicast addresses are for the limits inside the administrative boundaries. Since administratively scoped multicast addresses are locally assigned similar to private IPv4 addresses, they are not required to be unique across administrative boundaries. The administratively scoped multicast address block (239.0.0.0/8) addresses should be unique only within own administrative boundaries. Same address used in another administrative boundary should not create an address conflict issue. Multicast packets using 239.0.0.0/8 range are not to be forwarded beyond the network boundary.

Following are the further divisions in administratively scoped IPv4 multicast address space range - 239.0.0.0 to 239.255.255.255

Before continuing, please see an interesting excerpt from RFC 2365

RFC 2365 says that "The IPv4 Local Scope space grows ’downward’. As such, the IPv4 Local Scope may grow downward from 239.255.0.0/16 into the reserved ranges 239.254.0.0/16 and 239.253.0.0/16. However, these ranges should not be utilized until the 239.255.0.0/16 space is no longer sufficient.".

• Organization-Local scope expansion space (239.0.0.0 to 239.191.255.255) : These address space numerically below Organization-Local scope can be used as expansion space for the Organization-Local scope.
• Organization-Local scope 239.192.0.0/14 (239.192.0.0 to 239.195.255.255) : Organization-Local scope addresses are for private use within an organization for intersite applications.
• Site-Local scope expansion space (239.196.0.0 to 239.254.255.255) : The address range numerically below the Site-Local scope is intended as expansion space for the Site-Local Scope.
• Site-Local scope - 239.255.0.0/16 (239.255.0.0 to 239.255.255.255) : Site-Local scope represent the smallest possible scope in the network and is not further divisible.