以太类型（EtherType）是一个在以太网帧中的占用两字节的字段，这一字段代表了在以太网帧中封装了何种协议。该字段首次出现在以太网II帧（Ethernet II framing）中，并在后来由IEEE制定为IEEE 802.3以太网标准。
概述
表示以太类型的数据全部大于0x0800。由于历史原因，以太网II型帧与以太网帧格式相同，在以太网II型帧中表示以太类型的字段与以太网帧中表示封装长度的字段相重合。为了避免歧义，根据IEEE 802.3x-1997规定，以太网类型必须大于1536（0x0600）。该数值是根据MTU在以太网帧最大为1500（0x05DC）而定的，该字段数值小于等于1500（0x05DC）的为以太网帧，大于等于1536（0x0600）的为以太网II型帧，而处在1501~1536的数据为未定义数据。[1]
对于非标巨型以太网帧，可能会在以太类型部分与标准定义产生冲突。对此IETF提出采用特殊的以太类型0x8870来表示这种以太网帧。[2]
部分以太类型
| 以太类型编号 | 代表协议 |
|---|---|
| 0x0800 | Internet Protocol version 4 (IPv4) |
| 0x0806 | Address Resolution Protocol (ARP) |
| 0x0842 | Wake-on-LAN[3] |
| 0x22F0 | Audio Video Transport Protocol as defined in IEEE Std 1722-2011 |
| 0x22F3 | IETF TRILL Protocol |
| 0x6003 | DECnet Phase IV |
| 0x8035 | Reverse Address Resolution Protocol |
| 0x809B | AppleTalk (Ethertalk) |
| 0x80F3 | AppleTalk Address Resolution Protocol (AARP) |
| 0x8100 | VLAN-tagged frame (IEEE 802.1Q) & Shortest Path Bridging IEEE 802.1aq[4] |
| 0x8137 | IPX |
| 0x8138 | IPX |
| 0x8204 | QNX Qnet |
| 0x86DD | Internet Protocol Version 6 (IPv6) |
| 0x8808 | Ethernet flow control |
| 0x8809 | Slow Protocols (IEEE 802.3) |
| 0x8819 | CobraNet |
| 0x8847 | MPLS unicast |
| 0x8848 | MPLS multicast |
| 0x8863 | PPPoE Discovery Stage |
| 0x8864 | PPPoE Session Stage |
| 0x8870 | Jumbo Frames[2] |
| 0x887B | HomePlug 1.0 MME |
| 0x888E | EAP over LAN (IEEE 802.1X) |
| 0x8892 | PROFINET Protocol |
| 0x889A | HyperSCSI (SCSI over Ethernet) |
| 0x88A2 | ATA over Ethernet |
| 0x88A4 | EtherCAT Protocol |
| 0x88A8 | IEEE Std 802.1Q - Service VLAN tag identifier (S-Tag) |
| 0x88AB | Ethernet Powerlink[来源请求] |
| 0x88CC | 链路层发现协议 (LLDP) |
| 0x88CD | SERCOS III |
| 0x88E1 | HomePlug AV MME[来源请求] |
| 0x88E3 | Media Redundancy Protocol (IEC62439-2) |
| 0x88E5 | MAC security (IEEE 802.1AE) |
| 0x88E7 | Provider Backbone Bridges (PBB) (IEEE 802.1ah) |
| 0x88F7 | Precision Time Protocol (PTP) over Ethernet (IEEE 1588) |
| 0x8902 | IEEE 802.1ag Connectivity Fault Management (CFM) Protocol / ITU-T Recommendation Y.1731 (OAM) |
| 0x8906 | Fibre Channel over Ethernet (FCoE) |
| 0x8914 | FCoE Initialization Protocol |
| 0x8915 | RDMA over Converged Ethernet (RoCE) |
| 0x892F | High-availability Seamless Redundancy (HSR) |
| 0x9000 | Ethernet Configuration Testing Protocol[5] |
| 0x9100 | VLAN-tagged (IEEE 802.1Q) frame with double tagging[6] |
并不是所有以太类型都记载在IEEE以太类型列表（页面存档备份，存于互联网档案馆）中. 例如ARP协议(以太类型为 0x0806),在列表中仅仅标示为"Symbolics, Inc., Protocol unavailable."
参考资料
外部链接
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