Linux 手動調整 25GbE 為 10GbE

有時候需要直接指定介面為 10GbE，先查詢一下目前網路介面支援的速度：

[root@liho ~]# ethtool ens10f0np0
Settings for ens10f0np0:
	Supported ports: [ FIBRE ]
	Supported link modes:   1000baseKX/Full
	                        10000baseKR/Full
	                        25000baseCR/Full
	                        25000baseKR/Full
	                        25000baseSR/Full
	Supported pause frame use: Symmetric
	Supports auto-negotiation: Yes
	Supported FEC modes: None	 RS	 BASER
	Advertised link modes:  1000baseKX/Full
	                        10000baseKR/Full
	                        25000baseCR/Full
	                        25000baseKR/Full
	                        25000baseSR/Full
	Advertised pause frame use: Symmetric
	Advertised auto-negotiation: Yes
	Advertised FEC modes: None	 RS	 BASER
	Speed: 10000Mb/s
	Duplex: Full
	Auto-negotiation: on
	Port: FIBRE
	PHYAD: 0
	Transceiver: internal
	Supports Wake-on: g
	Wake-on: g
        Current message level: 0x00000004 (4)
                               link
	Link detected: yes

目前跑在 10Gb 的速度。如果不想要讓他跑別的速度，可以用下列指令讓網路只跑 10GbE：

[root@liho ~]# ethtool -s ens10f0np0 autoneg on speed 10000 duplex full

[root@liho ~]# ethtool ens10f0np0
Settings for ens10f0np0:
	Supported ports: [ FIBRE ]
	Supported link modes:   1000baseKX/Full
	                        10000baseKR/Full
	                        25000baseCR/Full
	                        25000baseKR/Full
	                        25000baseSR/Full
	Supported pause frame use: Symmetric
	Supports auto-negotiation: Yes
	Supported FEC modes: None	 RS	 BASER
	Advertised link modes:  10000baseKR/Full
	Advertised pause frame use: Symmetric
	Advertised auto-negotiation: Yes
	Advertised FEC modes: None	 RS	 BASER
	Speed: 10000Mb/s
	Duplex: Full
	Auto-negotiation: on
	Port: FIBRE
	PHYAD: 0
	Transceiver: internal
	Supports Wake-on: g
	Wake-on: g
        Current message level: 0x00000004 (4)
                               link
	Link detected: yes

上面的設定. 不管怎麼換 GBICs 1G or 25G 都只能跑 10GbE。

如果想恢復原本可以跑多種速度可以先查 ethtool 的 man pages 說明：

[root@liho ~]# man ethtool
.
.
.
(omit)
           advertise N
                  Sets the speed and duplex advertised by autonegotiation.  The argument is a hexadecimal value using one or a combination of the following values:

                  0x001                       10baseT Half
                  0x002                       10baseT Full
                  0x004                       100baseT Half
                  0x008                       100baseT Full
                  0x80000000000000000         100baseT1 Full
                  0x40000000000000000000000   100baseFX Half
                  0x80000000000000000000000   100baseFX Full
                  0x010                       1000baseT Half               (not supported by IEEE standards)
                  0x020                       1000baseT Full
                  0x20000                     1000baseKX Full
                  0x20000000000               1000baseX Full
                  0x100000000000000000        1000baseT1 Full
                  0x8000                      2500baseX Full               (not supported by IEEE standards)
                  0x800000000000              2500baseT Full
                  0x1000000000000             5000baseT Full
                  0x1000                      10000baseT Full
                  0x40000                     10000baseKX4 Full
                  0x80000                     10000baseKR Full
                  0x100000                    10000baseR_FEC
                  0x40000000000               10000baseCR Full
                  0x80000000000               10000baseSR Full
                  0x100000000000              10000baseLR Full
                  0x200000000000              10000baseLRM Full
                  0x400000000000              10000baseER Full
                  0x200000                    20000baseMLD2 Full           (not supported by IEEE standards)
                  0x400000                    20000baseKR2 Full            (not supported by IEEE standards)
                  0x80000000                  25000baseCR Full
                  0x100000000                 25000baseKR Full
                  0x200000000                 25000baseSR Full
.
.
.
(omit)

把你要的速度加總，例如：0x20000 + 0x80000 + 0x80000000 + 0x100000000 + 0x200000000 = 0x3800a0000 就可以使用下列指令還原本來的速度：

[root@liho ~]# ethtool -s ens10f0np0 advertise 0x3800a0000