[CentOS] 3Com 3c940 moel only giving me 100 mb throughput to network switch
Les Mikesell
lesmikesell at gmail.com
Mon Nov 23 19:16:33 UTC 2009
Gilbert Sebenste wrote:
>
>>>
>>> As the subject states, I have a 3Com 3c940 Ethernet card to a 1 gb network
>>> switch. The switch detects it, but it only shows that it is giving me 100
>>> mb/sec throughput. That card is rated for 1 GB...is there a way to force
>>> it to try to use 1 GB/sec? System-config-network isn't helping me here.
>> Does ethtool say it is running at 1Gb? What is the source of the data?
>> Many things can't generate much more than 100Mb, especially going too
>> or from a disk.
>
> Nope, it says at 100 mb. I wonder why? Yep, I know I can only probably go
> somewhat faster, but it would be nice. Here's ethtool's output before I
> did something below...
>
> 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.
--
Les Mikesell
lesmikesell at gmail.com
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