[CentOS] 3Com 3c940 moel only giving me 100 mb throughput to network switch

Eero Volotinen eero.volotinen at iki.fi
Mon Nov 23 19:18:38 UTC 2009


>> ethtool eth0
>> 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:  10baseT/Half 10baseT/Full
>>                                  100baseT/Half 100baseT/Full
>>                                  1000baseT/Full
>>          Advertised auto-negotiation: Yes
>>          Speed: 100Mb/s
> 
> I'd expect that to mean that it was connected to a 100Mb switch port or 
> a managed switch configured to force 100Mb.
> 
>> But then I tried this. Typing:
>>
>> ethtool --change eth0 speed 1000 duplex full autoneg on
>>
>> DID work! But I wonder why it didn't pick up on that automagically.
> 
> But then that wouldn't have worked either.
> 
>> And thanks, Les, for the ethtool reminder/tip!
> 
> Mii-tool does some of the same things but won't show/force 1000BaseT. 
> Also, you can put ETHTOOL_OPTS=... in your ifcfg-eth? files if you need 
> to force something odd.
> 

Are you using cat 5e or cat 6 (gigabit certified) cable?

--
Eero


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