Where ethNUMBER comes from?

xeon123 · 08-31-2012, 05:32 AM

I've changed the Motherboard of my pc, and when I restart it, I didn't got internet. I checked if I was acquiring IP with 'ifconfig' and I noticed that the PC wasn't getting IP for eth1. I checked the interfaces file in ubuntu and the OS was trying to acquire for eth0. So, I changed the /etc/network/interfaces auto eth0 to auto eth1. Now, everything works.

1 - Where ethNUMBER name is defined? Is it in the BIOS?

ukiuki · 08-31-2012, 05:54 AM

In a simple way, if you have 1 wired network card, the system will set it as eth0 so the 1st device, if the system has 2 network cards then the 1st will be eth0 and the 2nd will be eth1 and so on. You did change the motherboard but not the hard drive and you still have the same OS(is that correct?), if is that so the OS see this network card as a new card and second card in the system(eth1) and can't find eth0 because it isn't there, and previous settings were for eth0. So eth0 is present in the OS but there is no hardware. I hope this clarify your question.

Regards

linuxxer · 08-31-2012, 07:18 AM

Try this command :

Code:

cat /proc/net/dev

Quote:

Originally Posted by xeon123

I've changed the Motherboard of my pc

Newer Linux uses udev to configure device dynamically.
So I think It will work well with new hardware configuration.
But system create some udev rules for hard disk and network cards, .... for consistant naming of device.
This rule uses product ID, Vendor ID kind of details for naming.
In your case it may be problem

My system uses /etc/udev/rules.d/70-persistent-net.rules file for network card naming.

Udev device naming related configuration stored in,
/lib/udev/rules.d and /etc/udev/rules.d/.
So check these directories.

schneidz · 08-31-2012, 07:58 AM

Quote:

Originally Posted by ukiuki

In a simple way, if you have 1 wired network card, the system will set it as eth0 so the 1st device, if the system has 2 network cards then the 1st will be eth0 and the 2nd will be eth1 and so on. You did change the motherboard but not the hard drive and you still have the same OS(is that correct?), if is that so the OS see this network card as a new card and second card in the system(eth1) and can't find eth0 because it isn't there, and previous settings were for eth0. So eth0 is present in the OS but there is no hardware. I hope this clarify your question.

Regards

fyi, i have 1 network card but it checks in as eth3:

Code:

[schneidz@hyper ~]$ ifconfig -a
eth3      Link encap:Ethernet  HWaddr 90:FB:A6:2A:xx:xx  
          inet addr:192.168.1.25  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::92fb:a6ff:fe2a:5b68/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:309471 errors:10 dropped:0 overruns:10 frame:0
          TX packets:159555 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:267573302 (255.1 MiB)  TX bytes:301464658 (287.4 MiB)
          Interrupt:23 Base address:0x8000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:117 errors:0 dropped:0 overruns:0 frame:0
          TX packets:117 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:13950 (13.6 KiB)  TX bytes:13950 (13.6 KiB)

xeon123 · 08-31-2012, 08:39 AM

linuxxer, I think you're right. I've eth1 instead of eth0 because of the file '/etc/udev/rules.d/70-persistent-net.rules' like you said. If I clean this file maybe I would get now the network card eth0 instead of eth1. I will try that later.

schneidz · 08-31-2012, 08:42 AM

fyi heres mine:

Code:

[schneidz@hyper ~]$ cat /etc/udev/rules.d/70-persistent-net.rules

# This file was automatically generated by the /lib/udev/write_net_rules
# program run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single line.

# Networking Interface (rule written by anaconda)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="90:fb:a6:2a:5b:68", ATTR{type}=="1", KERNEL=="eth*", NAME="eth3"

ukiuki · 08-31-2012, 09:11 AM

Quote:

Originally Posted by schneidz

fyi, i have 1 network card but it checks in as eth3

This is interesting, has this been changed manually? Or does your distribution set that way as default? Usualy the 1st device is set as eth0, but that doesnt mean it can't be changed later.

Regards

xeon123 · 08-31-2012, 11:04 AM

ukiuki, it's because of this file: /etc/udev/rules.d/70-persistent-net.rules

ukiuki · 08-31-2012, 12:03 PM

Quote:

Originally Posted by xeon123

ukiuki, it's because of this file: /etc/udev/rules.d/70-persistent-net.rules

I know it is set in that file, still that isn't what the question is about so again and:
@schneidz: has this been changed manually? Or does your distribution set that way as default?

Regards

schneidz · 08-31-2012, 12:10 PM

i didnt change it... didnt even know about that file. fedora must've done something crazy.

ukiuki · 08-31-2012, 12:32 PM

Reminds me why I drop that distro, crazy things indeed !!

Regards

m1chel · 08-31-2012, 01:04 PM

It is not crazy. This is a udev 'feature'. The new LAN card/controller on your motherboard has a different MAC address than the previous ones. This will add to the udev persistent rules. Simply delete this file, and have udev build it again on next boot. Then you should have eth0 again.

I have seen this also with Gentoo. The distro I use.

Michel

ukiuki · 08-31-2012, 06:24 PM

Quote:

Originally Posted by m1chel

... Simply delete this file, ...Michel

Talking about crazy things, just make sure to make a backup of that file, just in case, so crazy things don't happen, also have a live cd in hand.
Wasn't Van Gogh from Holland? He was crazy yes? Great painter thou, crazy !!
I'm just kidding no offense.

Regards