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I have setup a network which fully supported 1000Mb/s speed. Same network shows 1000Mb/s speed in Windows system but in Centos it is showing 100Mb/s speed. Why?

My ethtool output as follow

 [root@localhost ~]# ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 2
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: on
        Supports Wake-on: pumbg
        Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes
Daniel
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Sohal Sharma
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    Is that a dual boot system or two different systems? If it's the second are they indeed connected to the same switch? Please include the output of `ethtool `. – HBruijn Jul 09 '14 at 07:38
  • No it is not dual boot. – Sohal Sharma Jul 09 '14 at 08:33
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    And could you update your question with the output of `ethtool`? – HBruijn Jul 09 '14 at 08:39
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    To me this sounds more like a hardware problem than a software problem. Maybe the switchport, the cable, or the NIC itself is faulty and not capable of operating at full speed. – kasperd Jul 09 '14 at 09:17
  • What is make /model of nic card ? Are you using in physical server ? Is this server are using dual boot between win/Centos It is possible to get out put from you are server following command. > ethtool ethX > > lshw -class network – user229912 Jul 09 '14 at 07:40
  • Yes I am using physical server. My system is not dual boot both are different systems. Yes I am able to get output from this command :- ethtool eth0 – Sohal Sharma Jul 09 '14 at 09:03
  • In windows it show 1000Mbps in linux it show 100mbps, Both have same cable and cisco gigabit unmanaged switch. – Sohal Sharma Jul 09 '14 at 10:47
  • Did you move the cable between the computers when testing? – kasperd Jul 09 '14 at 11:06
  • Yes I have move the cable between the computers when testing. – Sohal Sharma Jul 09 '14 at 11:16
  • Have you tried manually setting the duplex in the CentOS system? http://www.cyberciti.biz/tips/howto-linux-add-ethtool-duplex-settings-permanent.html – Byron C. Jul 09 '14 at 18:02
  • Does manually forcing gigabit speeds work i.e. `ethtool -s eth0 speed 1000 duplex full autoneg on` ? Auto-negotionation is required for gigabit but on some switches the negotiation doesn't always agree that Gigabit is supported by both sides :( – HBruijn Jul 09 '14 at 18:18
  • Yes I have done manually forcing gigabit speed using this:- ethtool -s eth0 speed 1000 duplex full autoneg on . But after doing this speed shows unknown and network goes down. – Sohal Sharma Jul 10 '14 at 09:58

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