100 lines
3.2 KiB
Markdown
100 lines
3.2 KiB
Markdown
---
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title: Changing the MAC address
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x-unreviewed: true
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...
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Introduction (GM45+e1000)
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=========================
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This section is applicable to all Libreboot-supported laptops with the
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mobile 4 series chipset (as shown in `$ lspci`)
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that use the e1000 ethernet controller (e.g. T400, X200).
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The R500 is an exception to this as it does not use the built-in e1000.
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On all these laptops, the
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[MAC address](https://en.wikipedia.org/wiki/MAC_address)
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for the built-in gigabit ethernet controller is stored inside the flash chip,
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along with Libreboot and other configuration data. Therefore, installing
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Libreboot will overwrite it.
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Thus, for these laptops, prebuilt Libreboot already contains a generic
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MAC address in the configuration section. This address is `00:f5:f0:40:71:fe
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in builds before 2018-01-16 and `00:4c:69:62:72:65` (see the ascii character
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set) afterwards.
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Unless you change it, your computer will boot and use it. This can lead
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to network problems if you have more than one Libreboot computer on
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the same layer2 network (e.g. on the same network switch). The switch
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(postman) will simply not know who to deliver to as the MAC (house) addresses
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will be the same.
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To prevent these address clashes, you can either modify prebuilt Libreboot
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to use an address of your own choosing or you can change the address in your
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operating system's boot scripts.
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In either case, it is a good idea to write down the address that your
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computer originally had.
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Obtaining the existing MAC address
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==================================
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The existing MAC address may be obtained by the following methods:
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1. Run `ip link` or `ifconfig` in a terminal/console/shell;
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find your ethernet device (e.g., **enpXXX** or **ethXXX**),
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and look for a set of 12 colon-delimited
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[hexadecimal digits](https://en.wikipedia.org/wiki/Hexadecimal).
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For example: `00:f3:f0:45:91:fe`.
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* `$ ip link
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... link/ether ??:??:??:??:??:?? brd ...
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* Alternatively:
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ifconfig
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... ether ??:??:??:??:??:?? txqueuelen ...
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2. Otherwise you can read the white label that is often found on the
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motherboard under the memory sticks:
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3. The MAC address is usually listed on the laptop chassis as well. This one
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will be incorrect if the motherboard was changed and the stickers were not
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updated.
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Changing the MAC address in the operating system
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================================================
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There are three portable ways of doing so:
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1. Using the new iproute2 package:
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ip link set <interface> down
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ip link set dev <interface> address 00:4c:69:62:72:65
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ip link set <interface> up
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2. Using the old `ifconfig` command:
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ifconfig <interface> hw ether 00:4c:69:62:72:65
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3. Using the macchanger package.
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You can use use of these three methods in your operating system's
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init scripts or you can use your operating system's own networking
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configuration. Refer to your operating system's documentation for
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how to do this.
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Changing the MAC address on X200/T400/T500/W500
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===============================================
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On GM45 laptops with ICH9M southbridge and Intel PHY module, the MAC address
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is hardcoded in boot flash, which means it can be changed if you re-flash.
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See [ich9utils documentation](../install/ich9utils.html)
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