Multicast Addresses

Multicast IP Addresses Overview

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.

multicast class D range

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:

AddressUsage
224.0.0.1All Hosts
224.0.0.2All Multicast Routers
224.0.0.3Unassigned
224.0.0.4DVMRP Routers
224.0.0.5OSPF Routers
224.0.0.6OSPF DR/BDR Router
224.0.0.7ST Routers
224.0.0.8ST Hosts
224.0.0.9RIPv2 Routers
224.0.0.10EIGRP Routers
224.0.0.11Mobile Agents
224.0.0.12DHCP Server / Relay
224.0.0.13All PIM Routers
224.0.0.14RSVP Encapsulation
224.0.0.15All CBT Routers
224.0.0.16Designated SBM
224.0.0.17All SBMS
224.0.0.18VRRP
224.0.0.19 – 255Unassigned

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

Table of Content

Unit 1. Introduction to Multicast

Unit 2: IGMP (Internet Group Management Protocol)

Unit 3: Multicast L2

Unit 4: Multicast L3

Unit 5:  IPv6 Multicast