Multicast L3 Addressing
Bits
-
IPv4 L3 multicast address always start with
1110or224.0.0.0/4 -
IPv6 L3 multicast address always start with
1111 1111orff00::/8
L3 Ranges
IPv4
IPv4 combines scope and purpose in its address ranges.
| Block | Name / Type | Notes |
|---|---|---|
224.0.0.0/4 | IPv4 Multicast | Entire IPv4 multicast space (Class D) |
224.0.0.0/24 | Local Control | Not routed (TTL=1). Used by OSPF, EIGRP, mDNS, etc. |
224.0.1.0/24 | Internetwork Control Block | Routable (e.g. NTP, some vendor protocols) |
232.0.0.0/8 | Source-Specific Multicast (SSM) | (S,G) only. No RP. Defined in RFC 4607 |
233.0.0.0/8 | GLOP Addressing | Derived from 16-bit ASN deprecated |
239.0.0.0/8 | Administratively Scoped | Private multicast (like RFC1918). |
IPv6
IPv6 separates scope cleanly by last nibble in the first hextet.
| Block | Address Scope | Description |
|---|---|---|
| ff00::/8 | Supernet | All IPv6 multicast addresses |
| ff01::/16 | Interface-Local | Stays within a single interface (rarely used in practice) |
| ff02::/16 | Link-Local | Local link only (no routing). Most control protocols live here |
| ff03::/16 | Realm-Local | Defined by an admin “realm” (rare / niche usage) |
| ff04::/16 | Admin-Local | Administrative domain (like a small org boundary) |
| ff05::/16 | Site-Local | Site scope (similar intent to IPv4 org-local, but loosely defined) |
| ff08::/16 | Organization-Local | Organization-wide scope (closest to 239.0.0.0/8 in spirit) |
| ff0e::/16 | Global | Globally routable multicast |
L3 addresses Combines IPv4 and IPv6
L3
IL — Interface-Local
- Node only
- Not transmitted
- Never on the wire
LL — Link-Local
- TTL of 1
- Transmitted
- On the wire
SL — Site-Local
- Routeable
- Not Global Internet
L2 and L3
- IPv4 is always
01:00:5e - IPv6 is always
33:33:00
| Protocol / Group | IPv4 | IPv4 L2 MAC | IPv6 LL | IPv6 L2 MAC |
|---|---|---|---|---|
| All Nodes | 224.0.0.1 | 01:00:5e:00:00:01 | ff02::1 | 33:33:00:00:00:01 |
| All Routers | 224.0.0.2 | 01:00:5e:00:00:02 | ff02::2 | 33:33:00:00:00:02 |
| OSPF All Routers | 224.0.0.5 | 01:00:5e:00:00:05 | ff02::5 | 33:33:00:00:00:05 |
| OSPF DR/BDR | 224.0.0.6 | 01:00:5e:00:00:06 | ff02::6 | 33:33:00:00:00:06 |
| RIPv2 / RIPng | 224.0.0.9 | 01:00:5e:00:00:09 | ff02::9 | 33:33:00:00:00:09 |
| EIGRP | 224.0.0.10 | 01:00:5e:00:00:0a | ff02::a | 33:33:00:00:00:0a |
| MLD | - | - | ff02::16 | 33:33:00:00:00:16 |
| VRRP | 224.0.0.18 | 01:00:5e:00:00:12 | ff02::12 | 33:33:00:00:00:12 |
| PIM / BSR | 224.0.0.13 | 01:00:5e:00:00:0d | ff02::d | 33:33:00:00:00:0d |
| IGMPv3 | 224.0.0.22 | 01:00:5e:00:00:16 | - | - |
| Cisco Auto-RP Announce | 224.0.1.39 | 01:00:5e:00:01:27 | - | - |
| Cisco Auto-RP Discovery | 224.0.1.40 | 01:00:5e:00:01:28 | - | - |
| NTP | 224.0.1.1 | 01:00:5e:00:01:01 | ff02::101 | 33:33:00:00:01:01 |
| mDNS | 224.0.0.251 | 01:00:5e:00:00:fb | ff02::fb | 33:33:00:00:00:fb |