[K12OSN] eth0 and eth1

James P. Kinney III jkinney at localnetsolutions.com
Sat Sep 13 01:52:40 UTC 2008

To add fun the eth0 or eth1 numbering madness, the initial ordering
during install is based on hardware initialization order. That order is
based on PCI bus addressing. Most system number devices physically
closer to the southbridge chip lower than than those further away. So a
PCI slot at the "bottom" of the board would be started later that one at
the "top" of the board. BUT (!!!) some board have PCI slots on bus 0 and
mobo parts on bus 1. Some boards have dual PCI bus's and alternate
numbering on the slots (gigabyte with a few Intel chips). Some reverse
all of this ad number up from the bottom of the board (thanks for the
ulcer, HP). The key thing is you can change things once installed. If
you have a 10/100 NIC that should be the upstream line, you can change
it to be that way. /sbin/ifconfig will show the ports and their IP
addresses. /etc/sysconfig/network-scripts has files ifcfg-eth0,
ifcfg-eth1, etc. Make backup copies, change the name, edit the file and
change the name IN the file Very Important!) and
tweak /etc/modprobe.conf. And do yourself a favor: put a label on the
outside of the box on the NIC itself saying eth0, IP address and MAC
address. A label machine or a nicely printed paper label with clear tape
will help keep sanity. (been there, done that too! :-)
James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC                           

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7

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