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vezult
Asked: 2011-03-30 04:37:04 +0800 CST

how do I disable autonegotation and force specific ethernet settings?

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I have a Dell r710 (running Debian GNU/Linux 6.0) which is currently in a datacenter hundreds of miles away, and the ethernet card is stuck at 10baseT half duplex. 10baseT is OK, but I want it to be full duplex.

The card in question is a broadcom BCM5709:

areion:~# lspci |grep Ethernet
01:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)
01:00.1 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)
02:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)
02:00.1 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)

using the bnx2 driver/firmware:

areion:~# apt-cache policy firmware-bnx2
firmware-bnx2:
  Installed: 0.28
  Candidate: 0.28
  Version table:
 *** 0.28 0
        500 http://ftp.us.debian.org/debian/ squeeze/non-free amd64 Packages
        100 /var/lib/dpkg/status

And running the stock kernel for squeeze:

areion:~# uname -a
Linux areion 2.6.32-5-amd64 #1 SMP Wed Jan 12 03:40:32 UTC 2011 x86_64 GNU/Linux

I've tried changing the ethernet settings:

ethtool -s eth0 speed 10 duplex full autoneg off

But then I lose all connectivity, and have to reboot the server in order to connect to it again. To avoid having to constantly reboot the server, and to find out if the ethtool command was hanging, I switched to using this script:

#!/bin/bash

ethtool -s eth0 speed 10 duplex full autoneg off 2>&1 > ethtool.log &

sleep 10
if [ $(jobs -r |wc -l) -gt 0 ]; then
   kill %1 || kill -9 %1
else
  echo '-----------' >> ethtool.log
  ethtool eth0 >> ethtool.log
fi
dmesg |tail > dmesg-recent.log

ethtool -s eth0 autoneg on

This allows me to see the status of the interface after running the command:

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:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Speed: Unknown!
        Duplex: Unknown! (255)
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: off
        MDI-X: Unknown
        Supports Wake-on: g
        Wake-on: d
        Link detected: no

From dmesg:

[  442.865157] bnx2: eth0 NIC Copper Link is Down

It seems that either autonegotation is failing, or the switch that I am plugged into is advertising 10Mbit/half duplex. I am told that the switch is running at 10M full duplex.

Might this be a driver issue, hardware issue, cable issue, switch issue? Is there anything I can do remotely to identify the source of the problem, or at least eliminate possibilities?

Update:

Turning autonegotiation off, and setting the options to 10/HD, 10/FD, 100/HD, 100/FD, etc (anything other than autonegotiated 10/HD) results in NO-CARRIER, as reported by ip link show dev eth0. The same is true for leaving autonegotiation on, and advertising anything other than 10/HD. Is there any way this could be something other than an issue with the switch?

linux ethernet

3 Answers

  1. It is better to have auto-negotiation enabled on both ends. This is the current recommendation of the networking vendors (including Cisco). See: http://www.cisco.com/en/US/tech/tk389/tk214/technologies_tech_note09186a0080094781.shtml

    For your problem, you have to find out how it is configured at the remote end. If it is auto-negotiation, then you should use auto-negotiation on your server too. If it is set at a specific speed and duplex you should match the remote end.

    Please keep in mind that is possible to keep the negotiation on and allow only negotiation for a certain speed and duplex. Also the advertising of capabilities can be configurable.

    If the network card has negotiated at 10/HD, this usually means that the remote end has negotiation disabled and it is set at 10/FD. Your bad performance is caused by the duplex mismatch.

    You should also try with a different network card. Changing the driver will not help because the detection of link (to detect the carrier and the speed) is done by PHY part of the NIC.

    • 3

  2. Can you put another device like a switch between you and the Server that you can change the settings on physically ? That might help.

    • 0

  3. It's not recommended to disable auto-negotiation, but if you still decide to, you must disable it on both ends and set both ends to use the exact same speed and duplex. If you only disable auto-negotiation on one end, the other end is forced to assume 10MB/HD. If you don't have access to the switch on the other end of the Ethernet cable or that switch does not support such customization, then disabling auto-negotiation is not an option. In some cases, you can leave auto-negotiation enabled, but tell the card or switch to advertise a lower speed or half-duplex.

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