I've /never/ seen RHEL/CentOS or any of its predecessors renumber ethernet ports on a working system..
Yeah, I have never seen it "re"number either?
I've seen it number them backwards, such that eth0 was the port labeled '1' outside the chassis and eth1 was port '0', but it was extremely consistent about this (one specific case of this I remember is RHEL2.1 or 3 on a Intel SE7501WV2 dual xeon board). I've had a pile of different RH linux configurations running on various servers for 10 or more years.
Here is a good explanation about this:
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc...
jlc