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Man Pages
EM(4) FreeBSD Kernel Interfaces Manual EM(4)

em
Intel(R) PRO/1000 Gigabit Ethernet adapter driver

To compile this driver into the kernel, place the following line in your kernel configuration file:
device em
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):
if_em_load="YES"

The em driver provides support for PCI Gigabit Ethernet adapters based on the Intel 82540, 82541ER, 82541PI, 82542, 82543, 82544, 82545, 82546, 82546EB, 82546GB, 82547, 82571, 81572, 82573, and 82574 Ethernet controller chips.
The em driver also provides support for PCI Express Gigabit Ethernet adapters based on the Intel 82575, 82576, 82580, i21x and i35x.
The driver supports Transmit/Receive checksum offload and Jumbo Frames on all but 82542-based adapters.
Furthermore it supports TCP segmentation offload (TSO) on all adapters but those based on the 82543, 82544 and 82547 controller chips. The identification LEDs of the adapters supported by the em driver can be controlled via the led(4) API for localization purposes. For further hardware information, see the README included with the driver.
For questions related to hardware requirements, refer to the documentation supplied with your Intel PRO/1000 adapter. All hardware requirements listed apply to use with FreeBSD.
Support for Jumbo Frames is provided via the interface MTU setting. Selecting an MTU larger than 1500 bytes with the ifconfig(8) utility configures the adapter to receive and transmit Jumbo Frames. The maximum MTU size for Jumbo Frames is 16114.
This driver supports hardware assisted VLANs. The em driver supports the following media types:
Enables auto-negotiation for speed and duplex.
Sets 10Mbps operation. Use the mediaopt option to select full-duplex mode.
Sets 100Mbps operation. Use the mediaopt option to select full-duplex mode.
Sets 1000Mbps operation. Only full-duplex mode is supported at this speed.
Sets 1000Mbps operation. Only full-duplex mode is supported at this speed.
The em driver supports the following media options:
Forces full-duplex operation
Forces half-duplex operation.
Only use mediaopt to set the driver to full-duplex. If mediaopt is not specified, the driver defaults to half-duplex.
For more information on configuring this device, see ifconfig(8).

The em driver supports Gigabit Ethernet adapters based on the Intel 82540, 82541ER, 82541PI, 82542, 82543, 82544, 82545, 82546, 82546EB, 82546GB, 82547, 82571, 82572, 82573, 82574, 82575, 82576, and 82580 controller chips:
  • Intel Gigabit ET Dual Port Server Adapter (82576)
  • Intel Gigabit VT Quad Port Server Adapter (82575)
  • Intel Single, Dual and Quad Gigabit Ethernet Controller (82580)
  • Intel i210 and i211 Gigabit Ethernet Controller
  • Intel i350 and i354 Gigabit Ethernet Controller
  • Intel PRO/1000 CT Network Connection (82547)
  • Intel PRO/1000 F Server Adapter (82543)
  • Intel PRO/1000 Gigabit Server Adapter (82542)
  • Intel PRO/1000 GT Desktop Adapter (82541PI)
  • Intel PRO/1000 MF Dual Port Server Adapter (82546)
  • Intel PRO/1000 MF Server Adapter (82545)
  • Intel PRO/1000 MF Server Adapter (LX) (82545)
  • Intel PRO/1000 MT Desktop Adapter (82540)
  • Intel PRO/1000 MT Desktop Adapter (82541)
  • Intel PRO/1000 MT Dual Port Server Adapter (82546)
  • Intel PRO/1000 MT Quad Port Server Adapter (82546EB)
  • Intel PRO/1000 MT Server Adapter (82545)
  • Intel PRO/1000 PF Dual Port Server Adapter (82571)
  • Intel PRO/1000 PF Quad Port Server Adapter (82571)
  • Intel PRO/1000 PF Server Adapter (82572)
  • Intel PRO/1000 PT Desktop Adapter (82572)
  • Intel PRO/1000 PT Dual Port Server Adapter (82571)
  • Intel PRO/1000 PT Quad Port Server Adapter (82571)
  • Intel PRO/1000 PT Server Adapter (82572)
  • Intel PRO/1000 T Desktop Adapter (82544)
  • Intel PRO/1000 T Server Adapter (82543)
  • Intel PRO/1000 XF Server Adapter (82544)
  • Intel PRO/1000 XT Server Adapter (82544)

Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5).
hw.em.disable_crc_stripping
Disable or enable hardware stripping of CRC field. This is mostly useful on BMC/IPMI shared interfaces where stripping the CRC causes remote access over IPMI to fail. Default 0 (enabled).
hw.em.eee_setting
Disable or enable Energy Efficient Ethernet. Default 1 (disabled).
hw.em.msix
Enable or disable MSI-X style interrupts. Default 1 (enabled).
hw.em.smart_pwr_down
Enable or disable smart power down features on newer adapters. Default 0 (disabled).
hw.em.sbp
Show bad packets when in promiscuous mode. Default 0 (off).
hw.em.rxd
Number of receive descriptors allocated by the driver. The default value is 1024 for adapters newer than 82547, and 256 for older ones. The 82542 and 82543-based adapters can handle up to 256 descriptors, while others can have up to 4096.
hw.em.txd
Number of transmit descriptors allocated by the driver. The default value is 1024 for adapters newer than 82547, and 256 for older ones. The 82542 and 82543-based adapters can handle up to 256 descriptors, while others can have up to 4096.
hw.em.rx_int_delay
This value delays the generation of receive interrupts in units of 1.024 microseconds. The default value is 0, since adapters may hang with this feature being enabled.
hw.em.rx_abs_int_delay
If hw.em.rx_int_delay is non-zero, this tunable limits the maximum delay in which a receive interrupt is generated.
hw.em.tx_int_delay
This value delays the generation of transmit interrupts in units of 1.024 microseconds. The default value is 64.
hw.em.tx_abs_int_delay
If hw.em.tx_int_delay is non-zero, this tunable limits the maximum delay in which a transmit interrupt is generated.

/dev/led/em*
identification LED device nodes

Make the identification LED of em0 blink:
echo f2 > /dev/led/em0
Turn the identification LED of em0 off again:
echo 0 > /dev/led/em0

em%d: Unable to allocate bus resource: memory
A fatal initialization error has occurred.
em%d: Unable to allocate bus resource: interrupt
A fatal initialization error has occurred.
em%d: watchdog timeout -- resetting
The device has stopped responding to the network, or there is a problem with the network connection (cable).

For general information and support, go to the Intel support website at: http://support.intel.com.
If an issue is identified with the released source code on the supported kernel with a supported adapter, email the specific information related to the issue to <freebsd@intel.com>.

altq(4), arp(4), iflib(4), led(4), netintro(4), ng_ether(4), polling(4), vlan(4), ifconfig(8)

The em device driver first appeared in FreeBSD 4.4. em was merged with the igb device driver and converted to the iflib framework in FreeBSD 12.0.

The em driver was originally written by Intel Corporation <freebsd@intel.com>. It was merged with igb driver and converted to the iflib framework by Matthew Macy <mmacy@mattmacy.io> and Sean Bruno <sbruno@FreeBSD.org>.
September 20, 2018 FreeBSD 12.0-RELEASE

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