This is a brand new SuperMicro X9SCL-F with an Intel 82579LM adapter and a fresh install of CentOS 6.2 with cPanel.

I am stuck at 10MBPS, I've tried everything. I've installed the latest 1.95 driver from Intel too, which seems to have fixed this problem for everyone else.

These commands do nothing.

ethtool -s eth1 speed 100 duplex half
ethtool -s eth1 speed 1000 duplex half
ethtool -s eth1 speed 100 duplex full
ethtool -s eth1 speed 1000 duplex full

They result with this in dmesg:

[ 1081.662365] e1000e 0000:02:00.0: eth1: Reset adapter
[ 1084.298376] e1000e: eth1 NIC Link is Up 10 Mbps Half Duplex, Flow Control: None
[ 1084.298443] e1000e 0000:02:00.0: eth1: Autonegotiated half duplex but link partner cannot autoneg. Try forcing full duplex if link gets many collisions.
[ 1084.298446] e1000e 0000:02:00.0: eth1: 10/100 speed: disabling TSO

This command knocks me off the network

ethtool -s eth1 speed ... autoneg off

Outputs

ethtool eth1

Settings for eth1:
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 pause frame use: No
Advertised auto-negotiation: Yes
Speed: 10Mb/s
Duplex: Half
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
MDI-X: off
Supports Wake-on: pumbag
Wake-on: g
Current message level: 0x00000001 (1)
Link detected: yes

ethtool -i eth1

driver: e1000e
version: 1.9.5-NAPI
firmware-version: 2.1-2
bus-info: 0000:02:00.0

Full dmesg:

[    2.332156] e1000e: Intel(R) PRO/1000 Network Driver - 1.2.20-k2
[    2.332159] e1000e: Copyright (c) 1999 - 2010 Intel Corporation.
[    2.332209] e1000e 0000:00:19.0: PCI INT A -> GSI 20 (level, low) -> IRQ 20
[    2.332225] e1000e 0000:00:19.0: setting latency timer to 64
[    2.332508] e1000e 0000:00:19.0: irq 31 for MSI/MSI-X
[    2.573664] e1000e 0000:00:19.0: eth0: (PCI Express:2.5GB/s:Width x1) 00:25:90:57:38:e5
[    2.573668] e1000e 0000:00:19.0: eth0: Intel(R) PRO/1000 Network Connection
[    2.573718] e1000e 0000:00:19.0: eth0: MAC: 10, PHY: 11, PBA No: FFFFFF-0FF
[    2.573777] e1000e 0000:02:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
[    2.573802] e1000e 0000:02:00.0: setting latency timer to 64
[    2.574078] e1000e 0000:02:00.0: irq 32 for MSI/MSI-X
[    2.574083] e1000e 0000:02:00.0: irq 33 for MSI/MSI-X
[    2.574088] e1000e 0000:02:00.0: irq 34 for MSI/MSI-X
[    2.574297] e1000e 0000:02:00.0: Disabling ASPM L0s 
[    2.657292] e1000e 0000:02:00.0: eth1: (PCI Express:2.5GB/s:Width x1) 00:25:90:57:38:e4
[    2.657296] e1000e 0000:02:00.0: eth1: Intel(R) PRO/1000 Network Connection
[    2.657380] e1000e 0000:02:00.0: eth1: MAC: 3, PHY: 8, PBA No: FFFFFF-0FF
[   14.181499] e1000e: eth1 NIC Link is Up 10 Mbps Half Duplex, Flow Control: None
[   14.181565] e1000e 0000:02:00.0: eth1: Autonegotiated half duplex but link partner cannot autoneg.  Try forcing full duplex if link gets many collisions.
[   14.181567] e1000e 0000:02:00.0: eth1: 10/100 speed: disabling TSO
[  476.773721] e1000e 0000:02:00.0: PCI INT A disabled
[  476.789823] e1000e 0000:00:19.0: PCI INT A disabled
[  476.935605] e1000e: Intel(R) PRO/1000 Network Driver - 1.9.5-NAPI
[  476.935608] e1000e: Copyright(c) 1999 - 2011 Intel Corporation.
[  476.935639] e1000e 0000:00:19.0: PCI INT A -> GSI 20 (level, low) -> IRQ 20
[  476.935651] e1000e 0000:00:19.0: setting latency timer to 64
[  477.008135] e1000e 0000:00:19.0: irq 31 for MSI/MSI-X
[  477.184223] e1000e 0000:00:19.0: eth0: (PCI Express:2.5GT/s:Width x1) 00:25:90:57:38:e5
[  477.184227] e1000e 0000:00:19.0: eth0: Intel(R) PRO/1000 Network Connection
[  477.184298] e1000e 0000:00:19.0: eth0: MAC: 11, PHY: 11, PBA No: FFFFFF-0FF
[  477.184309] e1000e 0000:02:00.0: Disabling ASPM L0s 
[  477.184393] e1000e 0000:02:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
[  477.184417] e1000e 0000:02:00.0: setting latency timer to 64
[  477.184836] e1000e 0000:02:00.0: irq 32 for MSI/MSI-X
[  477.184839] e1000e 0000:02:00.0: irq 33 for MSI/MSI-X
[  477.184841] e1000e 0000:02:00.0: irq 34 for MSI/MSI-X
[  477.334438] e1000e 0000:00:19.0: irq 31 for MSI/MSI-X
[  477.385281] e1000e 0000:00:19.0: irq 31 for MSI/MSI-X
[  477.386305] e1000e 0000:02:00.0: eth1: (PCI Express:2.5GT/s:Width x1) 00:25:90:57:38:e4
[  477.386308] e1000e 0000:02:00.0: eth1: Intel(R) PRO/1000 Network Connection
[  477.386458] e1000e 0000:02:00.0: eth1: MAC: 4, PHY: 8, PBA No: FFFFFF-0FF

Card is one of the following (not sure which):

00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (rev 05)
    Subsystem: Super Micro Computer Inc Device 1502
    Flags: bus master, fast devsel, latency 0, IRQ 31
    Memory at fba00000 (32-bit, non-prefetchable) [size=128K]
    Memory at fba24000 (32-bit, non-prefetchable) [size=4K]
    I/O ports at f020 [size=32]
    Capabilities: [c8] Power Management version 2
    Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
    Capabilities: [e0] PCI Advanced Features
    Kernel driver in use: e1000e
    Kernel modules: e1000e

02:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
    Subsystem: Super Micro Computer Inc Device 0000
    Flags: bus master, fast devsel, latency 0, IRQ 16
    Memory at fb900000 (32-bit, non-prefetchable) [size=128K]
    I/O ports at e000 [size=32]
    Memory at fb920000 (32-bit, non-prefetchable) [size=16K]
    Capabilities: [c8] Power Management version 2
    Capabilities: [d0] MSI: Enable- Count=1/1 Maskable- 64bit+
    Capabilities: [e0] Express Endpoint, MSI 00
    Capabilities: [a0] MSI-X: Enable+ Count=5 Masked-
    Capabilities: [100] Advanced Error Reporting
    Capabilities: [140] Device Serial Number 00-25-90-ff-ff-57-38-e4
    Kernel driver in use: e1000e
    Kernel modules: e1000e