[CentOS] Nic order detection
Barry Brimer
lists at brimer.org
Thu Jan 10 13:55:50 UTC 2008
> MatsK wrote:
>> Les Mikesell wrote:
>>> I have a number of machines that have 4 NICs, two of which are actually in
>>> use, running Centos 5. When they are rebooted, they seem to change the
>>> eth interface names, assigning them in different orders. I'm a little
>>> fuzzy on the details because they are at a remote location and I can't
>>> access them easily - especially after the network breaks. Shouldn't:
>>> alias eth0 bnx2
>>> alias eth1 bnx2
>>> alias eth2 e1000
>>> alias eth3 e1000
>>> in /etc/modprobe.conf always make the intel cards eth2 and 3?
>>
>> Noop, this is done with ifcfg-ethX where X is the if number.
>>
>> Create a /etc/sysconfig/network/ifcfg-eth0 that look like this example:
>>
>> DEVICE=eth0
>> HWADDR=00:01:23:45:67:89
>> ONBOOT=yes
>> TYPE=Ethernet
>> NETMASK=255.255.255.0
>> IPADDR=192.168.1.154
>> GATEWAY=192.168.1.1
>>
>> and then create ifcfg-eth1, ifcfg-eth2, ifcfg-eth3
>>
>> then do a "service network restart" to activate the settings.
>
> I do have the ifcfg-ethX files for the 2 interfaces that are currently
> active, but since the machines were built by image copies of a master disk,
> they do not have HWADDR address entries. A person on-site with access to the
> console adjusted them if they didn't come up right the first time, but they
> seem to shift around on each reboot. Will adding the HWADDR entry nail them
> down even if it doesn't match the nic type specified in modprobe.conf? Can
> someone point me to the code where this happens? Until recently the machines
> were running centos 3.x and this seems to be a difference in behavior.
In my experience, adding the HWADDR line to your ifcfg-ethX files will tie
the network interface to the right card, regardless of modprobe.conf
entries. I usually remove HWADDR lines when anaconda provides them at
install time because if I replace a nic (which obviously has a different
MAC address) without updating the HWADDR line, the interface fails to
start. In cases where modprobe.conf is unable to order the interfaces as
I want it to, I add HWADDR lines. Works every time.
Hope this helps.
Barry
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