Sunday, September 12, 2010

BSCI - Multicast - Address scopes

Multicast uses a reserved Class D with the first 4 high order bits in the 1st octet assigned 1110.

Therefore you can work out that the address range assigned for Multicast is 224.0.0.0 to 239.255.255.255

IANA then broke the address scope down further:
1) Locally Scoped, Reserved Link Local, addresses:
224.0.0.0 to 224.0.0.255
This range is the IANA 'well known' multicast range which includes your addresses for EIGRP (224.0.0.10), OSPF (224.0.0.5 and 224.0.0.6) RIPv2 (224.0.0.9) PIMv2 (224.0.0.13)

2) Globally Scoped addresses: - 224.0.1.0 to 238.255.255.255
-These can be allocated dynamically across the internet
-GLOP addresses fall into this scope (233.0.0.0/8)
-224.2.X.X was allocated to the 'MBone' or Multicast Backbone which is now a defunct technology due to little uptake by large institutions and the resources required by the equipment to manage the multicast traffic.

3) Limited (administratively) scoped addresses: - 239.0.0.0 to 239.255.255.255
- Reserved for inside corporate networks, similar to private IP's
- Organisations can use limited scoped addresses for local multicast apps

This range was further subdivided in to:
239.192.0.0 to 239.251.255.255
- Organisation wide scoped addresses

239.255.0.0/16 - site local address.

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