Getting only 100 Mbit/s from gigabit ethernet card

Hi,

I have the following problem. I bought two TP-LINK TG-3269 gigabit cards, placed them in two computers and connected them directly. On my Ubuntu system I used iperf tool and measured only 95 Mbit/s. It wont go any faster, I tried many times with different settings.

What is the problem? The indicator lamp shows 1000 Mbit/s.
5 answers Last reply
More about getting mbit gigabit ethernet card
  1. Many Gigabit cards will only negotiate a 100Mbps connection with a crossover cable or in crossover mode. You must connect a Gigabit switch in between to get full speed.
  2. 1. check the cable. It needs to be a cat5 with all 8 wires working. Basic cable testers are very cheap by the way. A crossover or switch is not needed for gigabit.
    2. you can set the speed manually somewhere in the driver, but i'm not an expert for linux. Research yourself.
  3. it is not the cable, i am pretty sure, nor is it auto negotiated 100Mbit/s speed...

    this is what I get on both computers with ethtool :

    Settings for eth0:
    Supported ports: [ TP MII ]
    Supported link modes: 10baseT/Half 10baseT/Full
    100baseT/Half 100baseT/Full
    1000baseT/Half 1000baseT/Full
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Advertised link modes: 10baseT/Half 10baseT/Full
    100baseT/Half 100baseT/Full
    1000baseT/Half 1000baseT/Full
    Advertised pause frame use: Symmetric Receive-only
    Advertised auto-negotiation: Yes
    Link partner advertised link modes: 10baseT/Half 10baseT/Full
    100baseT/Half 100baseT/Full
    1000baseT/Half 1000baseT/Full
    Link partner advertised pause frame use: Symmetric Receive-only
    Link partner advertised auto-negotiation: Yes
    Speed: 1000Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 0
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: pumbg
    Wake-on: g
    Current message level: 0x00000033 (51)
    drv probe ifdown ifup
    Link detected: yes


    everything is ok here...

    and mii-tool says: eth0: negotiated 1000baseT-HD flow-control, link ok
  4. it is not the cable, i am pretty sure, nor is it auto negotiated 100Mbit/s speed...

    this is what I get on both computers with ethtool :

    Settings for eth0:
    Supported ports: [ TP MII ]
    Supported link modes: 10baseT/Half 10baseT/Full
    100baseT/Half 100baseT/Full
    1000baseT/Half 1000baseT/Full
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Advertised link modes: 10baseT/Half 10baseT/Full
    100baseT/Half 100baseT/Full
    1000baseT/Half 1000baseT/Full
    Advertised pause frame use: Symmetric Receive-only
    Advertised auto-negotiation: Yes
    Link partner advertised link modes: 10baseT/Half 10baseT/Full
    100baseT/Half 100baseT/Full
    1000baseT/Half 1000baseT/Full
    Link partner advertised pause frame use: Symmetric Receive-only
    Link partner advertised auto-negotiation: Yes
    Speed: 1000Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 0
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: pumbg
    Wake-on: g
    Current message level: 0x00000033 (51)
    drv probe ifdown ifup
    Link detected: yes


    everything is ok here...

    and mii-tool says: eth0: negotiated 1000baseT-HD flow-control, link ok
  5. Quote:
    and mii-tool says: eth0: negotiated 1000baseT-HD flow-control, link ok


    There's your issue. The connection is only half-duplex (HD)
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