123 lines
4.2 KiB
Markdown
123 lines
4.2 KiB
Markdown
---
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title: Changing the MAC address
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x-toc-enable: 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 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 Canoeboot and other configuration data. Therefore, installing
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Canoeboot will overwrite it.
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Thus, for these laptops, prebuilt Canoeboot images already contain a generic
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MAC address in the GbE region.
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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 Canoeboot computer on
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the same layer2 network (e.g. on the same network switch).
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To prevent these address clashes, you can either modify prebuilt Canoeboot
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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 (OBSOLETE)
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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.md)
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If *all* you want to do is change the MAC address, you might try `nvmutil`
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instead. See notes below:
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Changing the MAC address via nvmutil
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-----------------------------------------------------------------
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Nowadays, nvmutil is the preferred way to do it, instead of ich9gen.
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See [nvmutil documentation](../install/nvmutil.md)
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This tool was originally written for changing the MAC address on Intel
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Sandybridge, Ivybridge and Haswell platforms, but it can be used on any
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platform with a valid GbE region in flash, where an Intel Flash Descriptor
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is used; this includes older GM45+ICH9M machines supported by Canoeboot.
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The `ich9utils` program is more useful in an cbmk context, because it
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generates an entire Intel Flash Descriptor and GbE region from scratch;
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coreboot has a similar method in its build system, using its own utility
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called bincfg, but this tool is unused in cbmk.
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No tool like ich9utils exists for these boards yet, but cbmk includes the IFD
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and GbE files in-tree.
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You can use `nvmutil` to change the existing MAC address in a GbE region. This
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sets the "hardcoded" MAC address, typically a globally assigned one set by
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the vendor, but you can use local addresses, and you can use randomised MACs.
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