# Advice please. Can not change MAC address

## sdavydov2

I tried to change mac address of my ethernet card but i couldn't do it.

The card has 16 "digit" mac address.

ifconfig eth0 down

ifconfig eth0 hw ether 11:22:33:44:55:66:77:88:99:10:11:12::13:14:15:16

-> And gentoo tells me invalid address.

What is wrong?

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## vad3r

First of all: A MAC address has 12 characters. It's almost impossible that your MAC address contains only digits. The command you supplied with your post can't work (12 != 32). Please review your ifconfig output. Btw why do you want to change your MAC address??

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## sdavydov2

I want to access one network to install Gentoo! and i don't want to speak with admin and ask him. ))

When i type "ifconfig eth0" it shows me following address "00-E0-18-00-03-A0-53-3D-00-00-00-00-00-00-00-00".  So it's 32 digits! 

The address i showed before was an example. And i windows i can easily change it.

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## modified_bessel

In order to sign onto some networks, your computer IP address may be identified by your computer's GUID number, not only its MAC number.  Sometimes non-existent GUID numbers (older motherboards) can be hacked by appending 20 zeros to the MAC address giving a 32 digit number like you have.  However, it looks like you have 16 zeros appended to 4 other digits (533D), and this probably means your board has a real GUID number recognized by the network.  I would guess that your actual (and changable) MAC address (ALWAYS 12 digits like vad3r says) is  00:E0:18:00:03:A0

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## sdavydov2

I try to change only 12 digits and i doesn't work also.

"ifconfig eth0 hw ether 00:15:C5:1D:33:6C"

Gento says: "SIOCSIFHWADDR: Invalid argument."

The strange thing is that Windows show MAC address as "00-1D-60-47-72-8B"

and in Gentoo: "HWaddr 00-E0-18-00-03-A0-53-3D-00-00-00-00-00-00-00-00"

???why???

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## tarpman

An Ethernet MAC address is only 6 bytes (12 hex digits) long.  That eth0 of yours is a Firewire (ethernet-over-1394) interface, as evidenced by the longer MAC.  Perhaps you have an eth1 which is your internet interface; or perhaps you're missing support for your network device in your kernel.

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## modified_bessel

Agreed..... Windows is looking at the ethernet card.  Interesting coincidence that the 8-byte firewire address + 16 hex zeros is equivalent to a 6-byte MAC address + 10-byte motherboard id = GUID (both 16 bytes and with similar formatting)

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## sdavydov2

Thanks a lot for information.   :Exclamation: 

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