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Re: [K12OSN] Network unreachable.



James P. Kinney III wrote:
This is beginning to sound like a module loading issue. Because you are
swapping out cards presumably with different drivers and certainly with
different MAC addresses, each change will require updating the
configuration of the devices.  I am unclear on what distro you are
running.
Second note. Modules get loaded in the order they are found in a file
called /etc/modules.conf (for current systems. Older systems
used /etc/conf.modules). However many motherboards try to power on
devices based on bus ID. That is typically done low number to high based
on slot location physically relative to the CPU location. So the top pci
slot is 0, the next one down is 1. But some boards do this in reverse
(high to low). So the removal of the second nic causes the first nic to
function properly which suggests the configuration of the second is out
of order, has the wrong MAC on both, or all of the above. The mii-tool
mentioned earlier will give you data on the interface specifics as well
as providing a means to adjust hardware settings (like full-duplex,
etc).

In recent 2.6 kernels (Centos 5.x, probably FC6), at least some of the device detection operations happen in parallel to speed up booting. A side effect is that which nic is initially called eth0/eth1 (etc.) is essentially random even if you have modules specified in modprobe.conf for certain types. However, when the configuration is applied as the network is started, if the /etc/sysconfig/network-scripts/ifcfg-eth? has HWADDR= values that match, the corresponding interface is renamed and used. If you use the GUI tools to set up the interfaces or they haven'b been changed since the initial install, the HWADDR addresses should be correct. If you copy a working machine to a new server or swap NIC cards you have to fix the HWADDR to match. Earlier kernels didn't require this because you could count on the device detection to always happen in the same order and the matching ifcfg-eth? would be applied even if you removed the HWADDR entry.

--
  Les Mikesell
   lesmikesell gmail com


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