[CentOS] RTL8111/8168B always 100mbps

[Brian Mathis]

On Tue, Sep 27, 2011 at 9:47 AM,  <m.roth at 5-cent.us> wrote:
> John Doe wrote:
>> From: Muhammad Panji <sumodirjo at gmail.com>
>>
>>> I have an onboard Realtek RTL8111/8168B NIC. from lspci -vv :
>>> 02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
>>> RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 02)
>>> It is detected, but why the speed is always 100Mbps, already change
> <snip>
>> I tried:
>> # ethtool -s eth0 speed 1000 duplex full autoneg off advertise 0x020
>> but auto-negotiation stays on and I only get 100Mbps...
>>
>> I tried:
>> # ethtool -s eth0 duplex full autoneg off advertise 0x020
>> auto-negotiation is off but nothing change...
>
> I was working on a similar problem (turned out to be our network switch),
> but *did* find that order of the ethtool command is significant: you
> *MUST* have autoneg off as the first parameter; that is, try
> # ethtool -s eth0  autoneg off speed 1000 duplex full advertise 0x020
>
>      mark


Auto-negotiation is a required part of the 1000Gb protocol.  You
cannot turn it off.

In the olden days there were a few problems with it, and some people's
reaction to every problem was to turn it off (and many made it the
default setting).  Some still repeat the mantra as if it is gospel,
but they are relics of a bygone era.  If your first reaction is to
disable auto-negotioation, please update your ways.  We are a decade
into the 21st century, after all.


-☙ Brian Mathis ❧-