Comments on: Random MAC address generator

By: x

Sat, 20 Apr 2013 13:45:41 +0000

The one from Holger is correct:
printf ‘%02x:’ $(( 0x$(od /dev/urandom -N1 -t x1 -An | cut -c 2-) & 0xFE | 0×02)) ; od /dev/urandom -N5 -t x1 -An | cut -c 2- | sed ‘s/ /:/g’

By: Hidayat

Hidayat — Mon, 03 Dec 2012 07:24:10 +0000

I am change mn my mac address but my computer not conectinge in conecting other wi-fi.in conctinge other computer this wi-fi.
in my password is carickd.

By: Hidayat

Hidayat — Mon, 03 Dec 2012 07:19:59 +0000

How to change mac address in nokia n8?

By: Holger

Holger — Mon, 02 Jul 2012 21:11:56 +0000

And with bash calculation use this:

printf ‘%02x:’ $(( 0x$(od /dev/urandom -N1 -t x1 -An | cut -c 2-) & 0xFE | 0×02)); \
od /dev/urandom -N5 -t x1 -An | cut -c 2- | sed ‘s/ /:/g’

By: Generate and Set a Random Valid MAC Address from the Command Line in OS X

Generate and Set a Random Valid MAC Address from the Command Line in OS X — Wed, 02 May 2012 17:20:29 +0000

[...] shown you how to generate MAC addresses randomly and then how to go about changing a MAC address in OS X Lion and OS X Mountain Lion, but why have [...]

By: waffletower

waffletower — Fri, 02 Mar 2012 09:18:16 +0000

The ruby snippet was broken. I don’t know ruby. I love perl though:

perl -e ‘printf “\n%02x:”, $x=(int(rand(128))*2); for($i=0;$i<4;$i++){printf "%02x:",$x=int(rand(256));}printf "%02x", $x=int(rand(256));printf"\n\n";'

By: How to spoof your MAC address in Mac OS X

How to spoof your MAC address in Mac OS X — Tue, 28 Feb 2012 20:33:07 +0000

[...] that value returned from ifconfig to another hex value in the format of aa:bb:cc:dd:ee:ff. You can generate a random one if need [...]

By: Hide the ‘Backup’ share of MyBook World Edition II in Mac OS X’s Finder « mackonsti

Thu, 20 Oct 2011 18:16:00 +0000

[...] note that the MAC address above is not the real one of my drives but a generated fake, for the sake of understanding the [...]

By: Steve

Steve — Thu, 07 Apr 2011 19:58:09 +0000

Thanks Ben and bob for this.

By: bob

bob — Thu, 17 Mar 2011 08:24:15 +0000

“(rand*64).to_i” should be written as “(rand 64)”
“(rand*256).to_i” should be written as “(rand 256)”

By: Ben Stoltz

Ben Stoltz — Thu, 11 Nov 2010 07:50:01 +0000

ruby -e ‘print (“%02x”%((rand*64).to_i*4|2))+(0..4).inject(“”){|s,x|s+”:%02x”%(rand*256).to_i} + “\n”‘

The result is a locally administered, non-multicast MAC address.

By: Matt

Matt — Wed, 10 Nov 2010 22:09:20 +0000

You need to be careful that this does not generate multicast mac addresses, as these are technically illegal as source macs. The strict definition of a multicast mac address is one where the least significant bit of the first byte is set to 1. So if the first octet’s LSB is 1 (01, 03,05, a1, etc) you technically have a multicast mac source. See http://en.wikipedia.org/wiki/MAC_address.

Using multicast src macs might not cause immediate connectivity problems, but certainly has implications for switches learning the mac address preventing unicast flooding, and routers allowing arp to resolve.

Cisco, for example, will not allow mac learning if the source is non-unicast, and Cisco routers will not install arp entries for multicast macs to unicast ip addresses.

I think you need to rethink this post taking into consideration these consequences.

By: first

first — Wed, 10 Nov 2010 18:02:29 +0000

I always just concoct random hex strings in my head, this is a bit less brain work so thanks