One of the differences between unicast and multicast IP addresses is that unicast IP addresses represent a single network device while multicast IP addresses represent a group of receives. IANA has reserved the class D range to use for multicast. The first 4 bits in the first octet are 1110 in binary, meaning we have the 224.0.0.0 through 239.255.255.255 range for IP multicast addresses.
Some of the addresses are reserved, however, and we can’t use them for our own applications.
The 224.0.0.0 – 224.0.0.255 range has been reserved by IANA to use for network protocols. All multicast IP packets in this range are not forwarded by routers between subnets. Let me give you an overview of reserved link-local multicast addresses. I’m sure you recognize some of the protocols:
| Address | Usage |
| 224.0.0.1 | All Hosts |
| 224.0.0.2 | All Multicast Routers |
| 224.0.0.3 | Unassigned |
| 224.0.0.4 | DVMRP Routers |
| 224.0.0.5 | OSPF Routers |
| 224.0.0.6 | OSPF DR/BDR Router |
| 224.0.0.7 | ST Routers |
| 224.0.0.8 | ST Hosts |
| 224.0.0.9 | RIPv2 Routers |
| 224.0.0.10 | EIGRP Routers |
| 224.0.0.11 | Mobile Agents |
| 224.0.0.12 | DHCP Server / Relay |
| 224.0.0.13 | All PIM Routers |
| 224.0.0.14 | RSVP Encapsulation |
| 224.0.0.15 | All CBT Routers |
| 224.0.0.16 | Designated SBM |
| 224.0.0.17 | All SBMS |
| 224.0.0.18 | VRRP |
| 224.0.0.19 – 255 | Unassigned |
You probably recognized OSPF (224.0.0.5 and 224.0.0.6), RIPv2 (224.0.0.9), and EIGRP (224.0.0.10). Once you dive more into multicast, you will also encounter PIM (Protocol Independent Multicast) with 224.0.0.13.
IANA also reserved the 224.0.1.0 /24 range for certain applications. Everything in the 224.0.1.0 /24 range can be routed, however, unlike the 224.0.0.0 /24 range. Here’s an overview:
Awesome post we’ve got here…
But a couple of things that didn’t quite sync in my mind.
First; When you mention that RIPv2 (224.0.0.9) and basically the range 224.0.0.0/24 is NOT routed between subnets, so my question is how RIPv2-aware routers advertise RIPv2 routes?
Second; Can you give an example of a work with 239.0.0.0/8, cos I fear that if I applied it on a typical LAN (where I’m restricted to use only private IP addresses) that is connected to the Internet, it cause a conflict… Ain’t that right?
Hi M. Bahwal,
Multicast traffic in the 224.0.0.0/24 range is processed by routers but it won’t be “routed” to another subnet. Imagine a couple of routers connected to each other to a switch. They’ll use 224.0.0.9 to communicate with each on this segment. These routers won’t forward these multicast packets to other interfaces.
What kind of multicast example are you looking for? There are many different configurations…
Best Regards,
Rene
“The 224.0.0.0 – 224.0.0.255 range h…”
I think multicast address range is 224.0.0.0-224.255.255.255
Hi Navin,
The 224.0.0.0 - 224.0.0.255 is a “special” range that IANA has assigned for certain applications, these addresses are not routed outside of the subnet. For example, RIPv2, OSPF, EIGRP, etc.
Rene
for 224 range : One such example could be “ospf hello” which is not a user traffic but traffic among routers and does not require to be routed.
where-in for 239 range …it is a multicast user traffic . thats how IANA has separated both range for multicast…is that correct to say?