為什麼我的 PLC（電力線轉換器）將速度除以 2？

如果我使用 CAT.5e 電纜直接連接到我的 100MB 路由器，我會得到以下結果：

$ speedtest --simple 
Ping: 8.617 ms
Download: 92.54 Mbit/s
Upload: 93.90 Mbit/s
$ ethtool eth0
Settings for eth0:
   Supported ports: [ TP MII ]
   Supported link modes:   10baseT/Half 10baseT/Full 
                           100baseT/Half 100baseT/Full 
   Supported pause frame use: No
   Supports auto-negotiation: Yes
   Advertised link modes:  10baseT/Half 10baseT/Full 
                           100baseT/Half 100baseT/Full 
   Advertised pause frame use: Symmetric Receive-only
   Advertised auto-negotiation: Yes
   Link partner advertised link modes:  10baseT/Half 10baseT/Full 
                                        100baseT/Half 100baseT/Full 
   Link partner advertised pause frame use: Symmetric Receive-only
   Link partner advertised auto-negotiation: Yes
   Speed: 100Mb/s
   Duplex: Full
   Port: MII
   PHYAD: 0
   Transceiver: internal
   Auto-negotiation: on
   Current message level: 0x00000033 (51)
                  drv probe ifdown ifup
   Link detected: yes

但是，如果我通過兩個dLAN® 200 AVmini PLC（一個電源線轉換器連接到路由器，另一個連接到我的 PC）連接到同一個路由器，我會得到：

$ speedtest --simple
Ping: 12.843 ms
Download: 43.86 Mbit/s
Upload: 49.06 Mbit/s
$ ethtool eth0
Settings for eth0:
   Supported ports: [ TP MII ]
   Supported link modes:   10baseT/Half 10baseT/Full
                           100baseT/Half 100baseT/Full
   Supported pause frame use: No
   Supports auto-negotiation: Yes
   Advertised link modes:  10baseT/Half 10baseT/Full
                           100baseT/Half 100baseT/Full
   Advertised pause frame use: Symmetric Receive-only
   Advertised auto-negotiation: Yes
   Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                        100baseT/Half 100baseT/Full
   Link partner advertised pause frame use: No
   Link partner advertised auto-negotiation: Yes
   Speed: 100Mb/s
   Duplex: Full
   Port: MII
   PHYAD: 0
   Transceiver: internal
   Auto-negotiation: on
   Current message level: 0x00000033 (51)
                  drv probe ifdown ifup
   Link detected: yes 

兩者的區別在於：

Ping: 8.617 ms                                                     |    Ping: 12.843 ms
Download: 92.54 Mbit/s                                             |    Download: 43.86 Mbit/s
Upload: 93.90 Mbit/s                                               |    Upload: 49.06 Mbit/s
   Link partner advertised pause frame use: Symmetric Receive-only|        Link partner advertised pause frame use: No

為什麼速度除以二，我該如何解決？

EDIT0：可以閱讀dLAN® 200 AVmini 產品表和HomePlug 維基百科文章。

您的電力線轉換器是按照舊標準（HomePlug AV，從 2005 年開始）建構的，不能提供非常好的性能。50Mbps 是您在使用此類轉換器的實際條件下獲得的速度。

我強烈建議您升級到根據 2012 年更新的 AV2 標準建構的轉換器。Devolo 的“Magic 1 LAN”是根據更新的標準建構的，應該提供更好的性能。

您可以嘗試將轉換器插入不同的插座。不要將它們插入延長線或電源板。您可能會發現配置更改可以讓您有所改進。

引用自：https://serverfault.com/questions/959370