看一个网卡最大能支持多大速度，不应该看lspci，而应该看ethtool的“Supported link modes”

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原文链接：https://access.redhat.com/solutions/758503

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#NIC #speed #50G #ethtool #max speed

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本文探讨了在Red Hat Enterprise Linux环境下，为何标称为1/10-Gigabit Server Adapter的网卡无法配置为10Gbps速度的问题。尽管lspci显示为10G适配器，但通过ethtool检查发现，该卡最大仅支持1Gbps。文章详细解释了原因在于硬件本身不支持10Gbps，并提供了如何确认网卡实际支持速度的步骤。

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Why interface speed of 10G (10000Mb/s) is not getting set on a '1/10-Gigabit Server Adapter' ?

SOLUTION 已验证 - 已更新 2014年三月19日05:18 -

English

环境

Red Hat Enterprise Linux (Any version)
NetXen Incorporated NX3031 Multifunction 1/10-Gigabit Server Adapter

问题

In lspci output, card is getting displayed as 1/10-Gigabit server adapter ,but still the maximum speed that can be configured is 1G (1000mb/s) , why ?
Below is the ethtool output:

Raw

Settings for eth2:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 2
        Transceiver: external
        Auto-negotiation: off
        Supports Wake-on: g
        Wake-on: g
        Link detected: yes

Setting a speed of 10000Mb/s fails with error.

决议

Even if the card reports 10G / 1/10-Gigabit Server Adapter in lspci output, but as per information from hardware vendor (HP) it is not capable of 10G.
As shown in ethtool the maximum speed which this card support is 1000baseT/Half 1000baseT/Full :

Raw

Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full <<---

根源

ethtool display the details fetched from the underlying hardware depending upon its supported features. If required feature is not seen then its an problem of underlying hardware. Here in this case HP confirmed that its not a 10G capable card even if in lspci output 1/10-Gigabit Server Adapter is seen.

诊断步骤

Check the maximum speed supported by NIC in ethtool ethX output against supported link modes field.
If there is no 10G seen (10000T/Half) seen, then in order to have 10gig speed, check with hardware vendor to find whether the underlying hardware has a support for 10Gig link speed or whether it requires any upgrades to support it.

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