3. 当前 IPv4 组播地址空间实践
IANA 分配 IPv4 组播地址已有多年历史。本备忘录阐述了 [IANA] 中反映的当前 IANA 实践，其依据是 RFC 2780 [RFC2780] 第 4.4.2 节所述的早期 IANA 实践。
| 地址范围 (Address Range) | 大小 (Size) | 名称 (Designation) |
|---|---|---|
| 224.0.0.0 - 224.0.0.255 | /24 | 本地网络控制块 (Local Network Control Block) |
| 224.0.1.0 - 224.0.1.255 | /24 | 互联网络控制块 (Internetwork Control Block) |
| 224.0.2.0 - 224.0.255.255 | /16 | AD-HOC 块 I (AD-HOC Block I) |
| 224.1.0.0 - 224.1.255.255 | /16 | 保留给 SIP (Reserved for SIP [RFC3261]) |
| 224.2.0.0 - 224.2.255.255 | /16 | SDP/SAP 块 (SDP/SAP Block) |
| 224.3.0.0 - 224.4.255.255 | /15 | AD-HOC 块 II (AD-HOC Block II) |
| 224.5.0.0 - 224.255.255.255 | 保留给未来分配块 (Reserved for future allocation blocks) | |
| 225.0.0.0 - 231.255.255.255 | 保留给未来分配块 (Reserved for future allocation blocks) | |
| 232.0.0.0 - 232.255.255.255 | /8 | 源特定组播块 (Source-Specific Multicast Block) |
| 233.0.0.0 - 233.251.255.255 | GLOP 块 (GLOP Block) | |
| 233.252.0.0 - 233.255.255.255 | AD-HOC 块 III (AD-HOC Block III) | |
| 234.0.0.0 - 238.255.255.255 | 保留给未来分配块 (含保留给未来管理员块的分配) (Reserved for future allocation blocks (including allocations reserved for future administrative blocks)) | |
| 239.0.0.0 - 239.255.255.255 | /8 | 管理范围块 (Administratively Scoped Block) |