IPv4 Multicast Addresses (224.0.0.0 – 239.255.255.255)
Understand IPv4 multicast addresses in the 224.0.0.0/4 range (Class D). Learn about well-known multicast groups, IGMP, and practical multicast use cases.
IPv4 Special
Detailed Explanation
IPv4 Multicast: 224.0.0.0/4
The 224.0.0.0/4 range (224.0.0.0 – 239.255.255.255) is reserved for IPv4 multicast traffic. Multicast allows a single source to send data to multiple receivers simultaneously without duplicating packets for each recipient.
Multicast Sub-ranges
| Range | Name | Scope |
|---|---|---|
| 224.0.0.0 – 224.0.0.255 | Local Network Control | Link-local, not forwarded by routers |
| 224.0.1.0 – 224.0.1.255 | Internetwork Control | May be forwarded |
| 239.0.0.0 – 239.255.255.255 | Administratively Scoped | Organization-local |
Well-Known Multicast Addresses
| Address | Purpose |
|---|---|
| 224.0.0.1 | All hosts on the local segment |
| 224.0.0.2 | All routers on the local segment |
| 224.0.0.5 | OSPF routers |
| 224.0.0.6 | OSPF designated routers |
| 224.0.0.9 | RIPv2 routers |
| 224.0.0.251 | mDNS (Bonjour / Avahi) |
| 224.0.0.252 | LLMNR (Link-Local Multicast Name Resolution) |
How Multicast Differs
Unicast: 1 sender → 1 receiver (point-to-point)
Broadcast: 1 sender → all devices (entire subnet)
Multicast: 1 sender → N subscribers (group members only)
Binary Representation
All Class D addresses start with the binary prefix 1110:
224.0.0.1: 11100000.00000000.00000000.00000001
239.255.255.255: 11101111.11111111.11111111.11111111
There is no concept of subnet mask for multicast addresses because they do not have network/host portions.
Use Case
A network engineer configures OSPF routing on an enterprise network, relying on the multicast address 224.0.0.5 for router discovery instead of unicast to reduce configuration overhead.