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Old 12-01-2009, 03:45 PM   #1
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Can Eth device names(or macs) be correlated to the physical eth port?

I am building a custom RedHat+<our-software> installer iso for our own appliance. Im using Red Hat 5.4. The appliances has two on-board eth interfaces. On the back panel of the appliance, these ports are marked 1 and 2.

When I install RH, I find the device names assigned such as eth0/eth1 are arbitrary. I understand this is to be expected with kernels 2.6+

Most of our customers connect their eth cables to the port marked 1 on the back and assume they should configure eth0 to make the device reachable. However, sometimes port 1 gets assigned eth1. This is not a blocking issue, but its going to confuse our customers and we wanted to make it easier on them.

From reading online discussion boards, I know HOW to switch the assignment of the eth names. However, what Im do not know is WHETHER I need to switch them at all. So I have two questions -

1)Is there anyway for me to tell which eth mac corresponds to which port on the back? Since they are soldered on the motherboard and not movable, I would think there would be some way to figure out that x mac address corresponds to the upper port (marked 1 etc).

2)Is there a way to tell this by running a linux command? We need to do this automatically so I need to be able to figure it out at install time from the kickstart post-install or similar.
Old 12-01-2009, 06:13 PM   #2
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The dmesg log will show you the relationship between the device name, irq, address, and MAC, for example:

dmesg | grep 'eth.*irq'
I'm guessing the mapping address at least will be consistent (and different) between the two interfaces, but I don't know what your ethernet hardware is.

You can also use lsdev in combination with ifconfig -a.

I take it the MAC addresses aren't labelled on the appliance (I'm assuming you will edit /etc/udev/rules.d/70-persistent-net.rules to force the device name based on MAC address).

Last edited by neonsignal; 12-01-2009 at 06:19 PM.


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