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{{PageHeader|Setting MAC address on iMX6ULL}}

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This article describes a couple of methods to set the board MAC address and avoid the assignment its random value after device reboot.

== Setting MAC address in systemd-networkd service files ==

The systemd-networkd interface configuration is stored in the *.network files within the ''/etc/systemd/network'' directory. To assign a MAC address to the chosen interface a new configuration file should be created (if it does not exist already). For the ''eth0'' interface a file named ''25-eth.network'' may be created with the following content:

<pre>
[Match]
Name=eth0

[Link]
MACAddress=fe:51:11:6c:62:e8

[Network]
DHCP=ipv4
</pre>

This file will assign the given address to the ''eth0'' interface and enable the DHCP client for IPv4 address setting. More information may be found on the systemd-networkd service documentation.

== U-Boot env variable ==

The default U-Boot configuration generates a random MAC address for the ETH interface. This behavior may be changed by adding a new env variable to the U-Boot. The environment variables are stored in one of the following files:

* StarSBC-6ULL ''include/configs/starsbc_6ull.h''
* StarSOM-6ULL ''include/configs/starsom_6ull.h''
* VisionSOM-6ULL ''include/configs/visionsom_6ull.h''

A new MAC address may be set by adding the following variable:

<pre>
ethaddr=fe:51:11:6c:62:e8
</pre>

== Linux device tree file ==

A MAC address may be defined in the dtb file used by the Linux kernel. The address definition should be added in the device tree source in the following section:

<pre>
&fec1 {
    local-mac-address = [ 70 b3 d5 1a 70 06 ];
}
</pre>

This code configures given MAC address for the ''fec1'' interface.

To prevent overwriting this value by u-boot, a random address generation should be disabled in the bootloader defconfig:

* StarSBC-6ULL ''configs/starsbc_6ull_defconfig''
* StarSOM-6ULL ''configs/starsom_6ull_defconfig''
* VisionSOM-6ULL ''configs/visionsom_6ull_defconfig''

<pre>
CONFIG_NET_RANDOM_ETHADDR=n
</pre>

== Processor OTP memory ==

{| class="frame-green"
|-
|'''NOTE!''' The described operation may be performed only once and cannot be reversed!
|}

The iMX6ULL processor has an OTP memory area that is used by default to store the permanent MAC address. The registers responsible for this are described in the Reference Manual:

* OTP Bank4 Word2 (MAC Address) (OCOTP_MAC0)
* OTP Bank4 Word3 (MAC Address) (OCOTP_MAC1)
* OTP Bank4 Word4 (MAC Address) (OCOTP_MAC2)

This area may be written from the U-Boot console by executing the following commands. In this example the '''fe:51:11:6c:62:e8''' address is stored in OTP:

<pre>
fuse prog 4 2 0x116c62e8
fuse prog 4 3 0xfe51
</pre>