Randomize router's MAC address

stynx · November 23, 2019, 7:48pm

Is there an easy way (like a package) to make my router randomize its MAC address on each boot?

sefralgon · November 23, 2019, 8:23pm

There is an incredibly easy way to do it. Just write a script and put it in /etc/rc.local for instance
Changing MAC address can be done with one command. Generating it can be other.

But why would you do that anyway?

slh · November 23, 2019, 9:10pm

Be aware that many clients (windows and android, probably iOS/ MacOSX as well) don't really like changing MAC addresses of their configured networks, doing so is a recipe for subtle issues. I realize that you might want to avoid your AP ending up in geolocation databases, but at the end of the day -unless you're quite literally living in the sticks- there'll always be enough other APs in range to make that a futile endeavour[0].

--
[0] what use is it to successfully fool google/ apple/ microsoft about your AP, if the neighbours' APs 6m left and right are loud and strong in their database.

stynx · November 24, 2019, 9:34pm

Because it's a travel router.

anon50098793 · November 25, 2019, 6:44pm

github.com

janost/openwrt-wan-mac/blob/master/wan-mac

#!/bin/sh /etc/rc.common

START=17

start() {
  OLDMAC=$(uci get network.wan.macaddr)
  logger "[WAN-MAC] Old WAN MAC address is ${OLDMAC}."
  NEWMAC=$(dd if=/dev/urandom bs=1024 count=1 2>/dev/null | md5sum | sed -e 's/^\(..\)\(..\)\(..\)\(..\)\(..\)\(..\).*$/\1:\2:\3:\4:\5:\6/' -e 's/^\(.\)[13579bdf]/\10/')
  logger "[WAN-MAC] Applying new random MAC address to WAN (${NEWMAC})..."
  uci set network.wan.macaddr=${NEWMAC}
  uci commit network
}

YMMV

mk24 · November 25, 2019, 9:33pm

It would be good to also set bit 1 of the first byte indicating it is a locally generated MAC. In other words acceptable values for the second digit are 2, 6, A, and E.