---
name: "em"
section: "4"
platform: "linux"
package: "freebsd-manpages"
version: "6.0-5"
release: "Debian 4.0 (Etch)"
platforms: ["linux", "freebsd", "openbsd"]
url: "https://new.carta.tech/em"
---

# em(4)

Intel(R) PRO/1000 Gigabit Ethernet adapter driver

## NAME

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

## SYNOPSIS

To compile support for the

**em** driver into your kernel, place the following line in your kernel configuration file:

**device em**

Alternatively, to load the

**em** driver 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 and 82573 Ethernet controller chips. The driver supports Transmit/Receive checksum offload and Jumbo Frames only on 82540, 82543, 82544 and 82546-based adapters. 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 version supports VLANs. For information on enabling VLANs, see the *README*. 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 and 82573 controller chips:

- 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 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)

## 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 additional information regarding building and installation, see the *README* included with the driver. 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 ⟨freebsdnic@mailbox.intel.com⟩.

## SEE ALSO

[arp(4)](/arp/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.

## AUTHORS

The **em** driver was written by Intel Corporation ⟨freebsdnic@mailbox.intel.com⟩.

## BUGS

Hardware-assisted VLAN processing is disabled by default. You can enable it on an **em** interface using [ifconfig(8)](/ifconfig/8.md).