Multiple NICs are flip-flopping

manya · 02-02-2014, 11:41 PM

Hi Guys,

I have a multi NIC PC with CentOS and have built a IPtables firewall. Now the issue I noticed is NICs IP address assigned originally gets changed every reboot and they are not persistent so every time I have to trace the cables and re-sit the Patch cords to make the connection work. Even I tried setting physical HW address in /etc/sysconfig/network-script but still no luck.

Any clue why this might be happening?

normanlinux · 02-03-2014, 04:32 AM

It looks as though your system is out of date.

The newer systemd configurations have solved this problem - at the expense of slightly more obtuse names than etho, eth1 etc.

See http://www.freedesktop.org/wiki/Soft...nterfaceNames/

akiuni · 02-03-2014, 08:56 AM

Hi

if normanlinux post doesn't solve your issue, you may have a look at the udev rules generator here :
/etc/udev/rules.d/70-persistent-net.rules

and try to fix the eth names by address mac addresses, like this :
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*",
ATTR{address}=="00:11:22:33:AA:EE",
ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

here is a post that may help you :
https://alteeve.ca/w/Changing_the_et...Mapping_in_EL6

manya · 02-03-2014, 10:11 PM

Its rather checkpoint built linux and its a customized linux, wondering what can be done but since its built on RHEL I believe all those concepts should be applied

Linux xxxxxxxxxx 2.6.18-92cp #1 SMP Wed Jul 24 20:30:29 IDT 2013 i686 i686 i386 GNU/Linux

Currently I dont see any rules under rules.d

ls /etc/udev/rules.d/
00-OS-XX.rules 05-udev-early.rules 50-udev.rules 51-hotplug.rules 66-raid-hotplug.rules 95-pam-console.rules

psycroptic · 02-04-2014, 09:49 PM

the file probably isn't there, you need to make it new.

also, i've found i can accomplish the same thing on ARch linux with /etc/udev/rules.d/10-network.rules:

Code:

SUBSYSTEM=="net", ATTR{address}=="MA:CA:DD:RE:SS", NAME="ethWhatever"

akiuni · 02-05-2014, 03:33 AM

Psycroptic's answer sounds good for me. I'd just like to add that if your flip flop is caused by MAC addresses changes (because you are running on a paravirtualized system or whatever...), you can also force udev to comply with the PCI plug order :

get the pci path to devices :

Code:

# ls -l /sys/class/net/eth*
lrwxrwxrwx 1 root root 0 Feb  5 09:23 /sys/class/net/eth0 -> ../../devices/pci0000:00/0000:00:03.0/net/eth0
lrwxrwxrwx 1 root root 0 Feb  5 09:23 /sys/class/net/eth1 -> ../../devices/pci0000:00/0000:00:08.0/net/eth1
lrwxrwxrwx 1 root root 0 Feb  5 09:23 /sys/class/net/eth2 -> ../../devices/pci0000:00/0000:00:09.0/net/eth2
lrwxrwxrwx 1 root root 0 Feb  5 09:23 /sys/class/net/eth3 -> ../../devices/pci0000:00/0000:00:0a.0/net/eth3

In your udev rule, force the eth names like that :

Code:

SUBSYSTEM=="net", KERNELS=="0000:00:03.0", NAME="eth0"
SUBSYSTEM=="net", KERNELS=="0000:00:08.0", NAME="eth1"
SUBSYSTEM=="net", KERNELS=="0000:00:09.0", NAME="eth2"
SUBSYSTEM=="net", KERNELS=="0000:00:0a.0", NAME="eth3"

That way, your ethernet devices order won't change if MAC addresses are not fiable.
note that the "KERNELS==" acts like a filter on the path, for example KERNELS=="03.0" would also match eth0.