I'm currently preparing BSCI certification exam, for my studdies I read the : Authorized Self-Studdy guide BSCI. In the chapter cover IP Multicast trafic, the author as wrote :
- Limited, or administratively, scoped addresses in the range 126.96.36.199 through 188.8.131.52. As defined by Requests for Comments (RFC) 2365, Administratively Scoped IP Multicast, these addresses are reserved for use inside private domains.
My understanding in this text is the following : address range 184.108.40.206/8 are multicast address which will only used on private network, like it is address define by the 1918 RFC for 10.0.0.0 network as exemple.
What I"m do not understand is the following :
"The administratively scoped multicast address space includes the following scopes, per the IANA:
- Site-local scope (220.127.116.11/16; 18.104.22.168/16, 22.214.171.124/16, and 126.96.36.199/16 are also reserved for this purpose)
- Organization local scope (188.8.131.52 to 184.108.40.206)
The IANA has further refined these ranges, as detailed in the IANA multicast address assignment list referenced earlier."
If 220.127.116.11 is already speficied for private used, why the author wrote, the IANA as defined different range also for private used in the range already defined for private used ?
Sorry for my English, I'm a French people it's also maybe why I do not understand the explanation provide by the author here !!
Thanks a lot !
The Reservations you are talking about are defined loosely with IPV6 context. I m showing the interesting part of the RFC
Partitioning of the Administratively Scoped Multicast Space
The following table outlines the partitioning of the IPv4 multicast
space, and gives the mapping from IPv4 multicast prefixes to IPv6
IPv6 SCOP RFC 1884 Description IPv4 Prefix
1 node-local scope
2 link-local scope 18.104.22.168/24
3 (unassigned) 22.214.171.124/16
5 site-local scope
8 organization-local scope 126.96.36.199/14
E global scope 188.8.131.52-184.108.40.206
Below is the explanation
An administratively scoped IP multicast region is defined to be a
topological region in which there are one or more boundary routers
with common boundary definitions. Such a router is said to be a
boundary for scoped addresses in the range defined in its
Network administrators may configure a scope region whenever
constrained multicast scope is required. In addition, an
administrator may configure overlapping scope regions (networks can
be in multiple scope regions) where convenient, with the only
limitations being that a scope region must be connected (there must
be a path between any two nodes within a scope region that doesn't
leave that region), and convex (i.e., no path between any two points
in the region can cross a region boundary). However, it is important
to note that if administratively scoped areas intersect
topologically, then the outer scope must consist of its address space
minus the address spaces of any intersecting scopes. This requirement
prevents the problem that would arise when a path between two points
in a convex region crosses the boundary of an intersecting region.
For this reason, it is recommended that administrative scopes that
intersect topologically should not intersect in address range.
Finally, note that any scope boundary is a boundary for the Local
Scope. This implies that packets sent to groups covered by
220.127.116.11/16 must not be forwarded across any link for which a
scoped boundary is defined.
If you know the IPV6 address, you will understand it easily. Refer IPv6 multicast addressing for further clarification
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