Intel® 82599 10 GbE 網卡

一般使用 1G 的網卡都可以透過 #ethtool 將速度降至 10/100 M , 但是 10G 的網卡可以嗎??目前有邊有一張 Intel® 82599 10 GbE Controller 想將他降到 1G 卻出現問題了!!

[root@benjr ~]# ethtool –s eth0 autoneg off speed 100

• Autoneg
  auto negotiation 的速度由網卡依據目前網路狀況自行決定.如果要自訂速度那第一步就要先將 auto negotiation 的功能關掉 autoneg off .
• speed
  除了 10M 以外,還有 100M,1G 等的速度可以做調整.

可以看到我的 1G 網卡支援 10baseT/Half ,10baseT/Full ,100baseT/Half ,100baseT/Full ,1000baseT/Full 等不同速度和半速 ( half ) 和全速 ( full) 可以選擇.

[root@benjr ~]# ethtool eth0 
Settings for eth0
          Supported ports: [ TP ]
          Supported link modes: 10baseT/Half 10baseT/Full
          100baseT/Half 100baseT/Full
          1000baseT/Full
          Supports auto-negotiation: Yes
          Advertised link modes: 10baseT/Half 10baseT/Full
          100baseT/Half 100baseT/Full
          1000baseT/Full
          Advertised auto-negotiation: Yes
          Speed: 100Mb/s
          Duplex: Full
          Port: Twisted Pair
          PHYAD: 1
          Transceiver: internal
          Auto-negotiation: on
          Supports Wake-on: pumbag
          Wake-on: g
          Current message level: 0×00000001 (1)
          Link detected: yes

但是我的 Intel® 82599 10 GbE Controller 看到有支援的速度只有 10000baseT/Full,這是不支援嗎??

[root@benjr ~]# ethtool eth3 
Settings for eth3
          Supported ports: [ FIBRE ]
          Supported link modes: 10000baseT/Full
          Supports auto-negotiation: No
          Advertised link modes: 10000baseT/Full
          Advertised auto-negotiation: No
          Speed: Unknown!
          Duplex: Unknown! (255)
          Port: FIBRE
          PHYAD: 0
          Transceiver: external
          Auto-negotiation: off
          Supports Wake-on: d
          Wake-on: d
          Current message level: 0×00000007 (7)
          Link detected: no

查了 Intel 的 82599 10 GbE 的晶片說明書,可以看到 http://download.intel.com/design/network/prodbrf/321731.pdf

1. 100 Mbps/1 Gbps/10 Gbps speeds
   Triple-speed support for backward-compatible implementations
2. Auto-negotiation support as defined in IEEE 802.3ap clause 73
   Provides automatic configuration between 1000BASE-KX, 10GBASE-KX4, and 10GBASE-KR mode

的確有支援,但是要怎麼做是要使用不同的 transceiver 嗎??? 答案我想是的,需要透過不同的 1G / 10G Transceiver 來調整 10G 網卡的速度.

如果使用 RJ45 的 transceiver 還需要 crossover(交叉線又稱為跳線) 嗎?

如果網卡或是 switch 本身有支援 Auto-MDIX (automatic medium-dependent interface crossover) 就表示他會自己偵測不再需要使用 crossover(交叉線又稱為跳線).