[CentOS] C7 and spoofed MAC address

Fri Jul 7 13:10:47 UTC 2017
Robert Moskowitz <rgm at htt-consult.com>

On 07/07/2017 02:13 AM, James Hogarth wrote:
> On 30 June 2017 at 18:58,  <m.roth at 5-cent.us> wrote:
>> Got a problem: a user's workstation froze. He wound up rebooting, without
>> calling me in first, so I dunno. But, and this is a show-stopper, when it
>> came up, it came up with the firmware MAC, not the spoofed one. In
>> /etc/sysconfig/network-scripts/ifcg-eth0, I've got the spoofed MAC
>> address, and a UUID. In the grub.conf, I've got net.ifnames=0
>> biosdevname=0. But when I logged onto his machine, ip a showed eth0... but
>> with the firmware MAC.
>> And I'm wondering if it went to renew its IP address, and lost the spoofed
>> MAC. That might explain his freezes.
>> Anyway, does anyone have any idea if there's some networkmangler or
>> systemd configuration that would force it to pay attention?
>> Note that my hack to fix it was ifdown eth0/ifup eth0, and it's fine.
> Not much to go on here ....
> Your ifcfg-* configs would be helpful.
> There was a slight change to MAC spoof behaviour in the NM 1.4.0 that
> was part of EL7.3 compared to the older NM as I recall
> https://www.hogarthuk.com/?q=node/18
> That may or may not be affecting you.

I am using Centos7-armv7hl and have had no problem altering my MAC 
address.  Much easier than back in Centos6.  All I have needed is in 
ifcfg-eth0 like:


No grub.conf but

cat /boot/extlinux/extlinux.conf
#Created by RootFS Build Factory
ui menu.c32
menu autoboot centos
menu title centos Options
#menu hidden
timeout 60
totaltimeout 600
label centos
     kernel /vmlinuz-4.9.30-203.el7.armv7hl
     append enforcing=1 root=UUID=ad25a528-baf4-469c-bd12-5276e8f5f9ae
     fdtdir /dtb-4.9.30-203.el7.armv7hl
     initrd /initramfs-4.9.30-203.el7.armv7hl.img

Oh, ip addr shows:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast 
state UP qlen 1000
     link/ether 02:67:15:00:e0:02 brd ff:ff:ff:ff:ff:ff
     inet brd scope global eth0
        valid_lft forever preferred_lft forever
     inet6 2601:4:2001:7302:67:15ff:fe00:e002/64 scope global 
noprefixroute dynamic
        valid_lft 2147448sec preferred_lft 604765sec
     inet6 fe80::67:15ff:fe00:e002/64 scope link
        valid_lft forever preferred_lft forever

BTW, the reason I change my MAC is to thus hand-craft my IPv6 address.  
6715 is my IANA Enterprise number and e002 is the IPv4 subnet address.  :)