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diff --git a/docs/hardware/mac_address.md b/docs/hardware/mac_address.md new file mode 100644 index 00000000..0a0d3621 --- /dev/null +++ b/docs/hardware/mac_address.md @@ -0,0 +1,107 @@ +--- +title: Changing the MAC address +... + +Introduction (GM45+e1000) +========================= + +This section is applicable to all Libreboot-supported laptops with the +mobile 4 series chipset (as shown in `$ lspci`) +that use the e1000 ethernet controller (e.g. T400, X200). +The R500 is an exception to this as it does not use the built-in e1000. + +On all these laptops, the +[MAC address](https://en.wikipedia.org/wiki/MAC_address) +for the built-in gigabit ethernet controller is stored inside the flash chip, +along with Libreboot and other configuration data. Therefore, installing +Libreboot will overwrite it. + +Thus, for these laptops, prebuilt Libreboot already contains a generic +MAC address in the configuration section. This address is `00:f5:f0:40:71:fe` +in builds before 2018-01-16 and `00:4c:69:62:72:65` (see the ascii character +set) afterwards. +Unless you change it, your computer will boot and use it. This can lead +to network problems if you have more than one Libreboot computer on +the same layer2 network (e.g. on the same network switch). The switch +(postman) will simply not know who to deliver to as the MAC (house) addresses +will be the same. + +To prevent these address clashes, you can either modify prebuilt Libreboot +to use an address of your own choosing or you can change the address in your +operating system's boot scripts. + +In either case, it is a good idea to write down the address that your +computer originally had. + +Obtaining the existing MAC address +================================== + +The existing MAC address may be obtained by the following methods: + +1. Run `ip link` or `ifconfig` in a terminal/console/shell; + find your ethernet device (e.g., **enpXXX** or **ethXXX**), + and look for a set of 12 colon-delimited + [hexadecimal digits](https://en.wikipedia.org/wiki/Hexadecimal). + For example: `00:f3:f0:45:91:fe`. + + * `$ ip link` + + `... link/ether ??:??:??:??:??:?? brd ...` + + * Alternatively: + + `$ ifconfig` + + `... ether ??:??:??:??:??:?? txqueuelen ...` + + +2. Otherwise you can read the white label that is often found on the + motherboard under the memory sticks: +  + +3. The MAC address is usually listed on the laptop chassis as well. This one + will be incorrect if the motherboard was changed and the stickers were not + updated. + +Changing the MAC address in the operating system +================================================ + +There are three portable ways of doing so: + +1. Using the new iproute2 package: + + `# ip link set <interface> down` + + `# ip link set dev <interface> address 00:4c:69:62:72:65` + + `# ip link set <interface> up` + + +2. Using the old `ifconfig` command: + + `# ifconfig <interface> hw ether 00:4c:69:62:72:65` + + +3. Using the macchanger package. + +You can use use of these three methods in your operating system's +init scripts or you can use your operating system's own networking +configuration. Refer to your operating system's documentation for +how to do this. + +Changing the MAC address in Libreboot +===================================== + +See [here](../gnulinux/grub_cbfs.md#changeMAC). + + + +Copyright © 2017 Fedja Beader <fedja@protonmail.ch> + +Copyright © 2014, 2015 Leah Rowe <info@minifree.org> + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License Version 1.3 or any later +version published by the Free Software Foundation +with no Invariant Sections, no Front Cover Texts, and no Back Cover Texts. +A copy of this license is found in [../fdl-1.3.md](../fdl-1.3.md) |