After replacing a Network card I was trying to reset the nework card with RH 'ifdown' & 'ifup' when I got the following error...
[root]# ifdown eth0
Device eth0 has different MAC address than expected, ignoring.
I was able to shut it down with...
[root]# ifconfig eth0 down
SOLUTION: Apparently PnP/Kudzu does nothing to check or reset a NICs hardware address after replacing one. This breaks RH ifdown/ifup commands, unless you manually edit the "HWADDR=" variable in these files. Using the /usr/sbin/system-config-network tool didn't seem to help much. I had to edit all three ifcfg-eth0 files, or last one to get ifdown command to work. Not sure why these files aren't linked either?
[root]# locate ifcfg-eth0
... oops, gui not very intuitive
[root]# /usr/sbin/system-config-network &
doublclick eth0 device
select "Hardware Device" tab
[Check] Bind to MAC address, then click PROBE