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-   -   gig NIC only connection 100 mbit. Connecting to gig switch. (

Foldarn 04-02-2009 09:47 AM

gig NIC only connects at 100 mbit. Connecting to gig switch.
I have a small fileserver. It's just used for myself and my wife for convenience. It's also used as a media server for our television.

I'm running it with Ubuntu 8.10 (Intrepid) on it.

It's running an Intel Atom motherboard as shown here:


The product spec sheet says the following about the on-board NIC:


The LAN, based on the RealTek RTL8111C Ethernet Controller, provides the following
functions: 10/100/1000 Mb/s Gigabit Ethernet LAN
I also tossed on a gigabit NIC as shown here:

NetGear GA311 Ver.A1

Both of these NICs connect ONLY at 100 mbit and I don't know why. At first the secondary NIC was connecting at gig speed. The motherboard network interface I'm not sure of at the start because it was only connected to a 100 mbit device on the other side.

The Netgear is connected to a Netgear 5 port gig switch. The switch has 2 indicator LEDs where if one LED is lit, it's 100 mbit. If both are lit, it's 1 gbit connection.

Transfer speeds originally were at 50 MB/sec when it was up on gigabit, limited only by the hard drive in the machine.

Transfer speeds with 100 mbit are as expected, 10-12 MB/sec.

The motherboard interface is using a Realtek RTL8111C chip.

The Netgear NIC uses a Realtek RTL8169 chip.

Can someone help me get these network interfaces connecting at gig speeds?

Foldarn 04-02-2009 09:47 AM

New information!

I can use the below command after a reboot and it will switch to gigabit speeds..... for awhile. Once it switches back to 100 mbit, if I try to use ethtool again, it takes a few seconds for the NIC to come back on, but when it does, it's still sitting there at 100 mbit.


sudo ethtool -s eth1 speed 1000 duplex full

bcromwell 04-02-2009 09:55 AM

try ethtool -s eth1 autoneg off speed 1000 duplex full
You shouldn't need to do this a RFC states gig is suppose to autoneg. I assume you using a cat5 ethernet cable.

Foldarn 04-02-2009 10:34 AM

bcromwell, it's Cat6 ethernet cable I'm using. 3 feet of it. It's brand new and only 3 feet long. However, after doing a little bit of research, I saw another post where someone had the same issue due to bad network cabling. If I do the ethtool you specified, it will NOT give me an active link light. Ever. Not until I redo the command and enable autoneg. Like I said, even then it just goes back to 100 mbit.

Unfortunately, I'm at work so I'm unable to test the cabling at this current time. :(

Foldarn 04-03-2009 07:04 PM

I've ruled out the cables. Ethernet cables that work perfect on my desktop running XP are now connected to one of my Linux boxes. So I'm currently laying the blame on either the NIC, the kernel, or the drivers, but I don't know what to do about it.

If I try and force it using


sudo ethtool -s eth1 speed 1000 duplex full
The link goes dead for about 5-10 seconds, then comes back alive still at 100 mbit.

If I execute this


sudo ethtool -s eth1 speed 1000 duplex full autoneg off
then the link goes dead and it does NOT come back up until I reinstate the autonegotiation. I'm totally at a loss here. :(

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