---
name: "em"
section: "4freebsd"
platform: "linux"
package: "freebsd-manpages"
version: "12.2-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/em/4freebsd"
---

# em(4freebsd)

Intel(R) PRO/1000 Gigabit Ethernet adapter driver

## NAME

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

## SYNOPSIS

To compile this driver into the kernel, place the following lines in your kernel configuration file:

**device iflib** **device em**

Alternatively, to load the driver as a module at boot time, place the following line in [loader.conf(5)](/loader.conf/5.md):

```
if_em_load="YES"
```

## DESCRIPTION

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)](/led/4.md) 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)](/ifconfig/8.md) 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:

- **autoselect**

  Enables auto-negotiation for speed and duplex.

- **10baseT/UTP**

  Sets 10Mbps operation. Use the **mediaopt** option to select **full-duplex** mode.

- **100baseTX**

  Sets 100Mbps operation. Use the **mediaopt** option to select **full-duplex** mode.

- **1000baseSX**

  Sets 1000Mbps operation. Only **full-duplex** mode is supported at this speed.

- **1000baseTX**

  Sets 1000Mbps operation. Only **full-duplex** mode is supported at this speed.

The **em** driver supports the following media options:

- **full-duplex**

  Forces full-duplex operation

- **half-duplex**

  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)](/ifconfig/8.md).

## HARDWARE

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)

## LOADER TUNABLES

Tunables can be set at the [loader(8)](/loader/8.md) prompt before booting the kernel or stored in [loader.conf(5)](/loader.conf/5.md).

- *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.

## FILES

- */dev/led/em\**

  identification LED device nodes

## EXAMPLES

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
```

## DIAGNOSTICS

- 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).

## SUPPORT

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*⟩.

## SEE ALSO

[altq(4)](/altq/4.md), [arp(4)](/arp/4.md), [iflib(4)](/iflib/4.md), [led(4)](/led/4.md), [netintro(4)](/netintro/4.md), [ng\_ether(4)](/ng_ether/4.md), [polling(4)](/polling/4.md), [vlan(4)](/vlan/4.md), [ifconfig(8)](/ifconfig/8.md)

## HISTORY

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.

## AUTHORS

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*⟩.