Definitive way to configure network devices in Centos 6.2

Question

What is the definitive way to configure network devices in Centos 6.2? Via network manager or editing /etc/sysconfig/network-scripts?

I have a notebook with 1 ethernet port and a usb ethernet adapter plugged in.

When I do ip link show I see eth0 and em1. However when I go to /etc/sysconfig/network-scripts, there is an ifcfg-eth0 file and ifcfg-usb0, but no ifcfg-em1.

The network manager applet shows under Wired connections System eth0 and System usb0. I have set eth0 to 10.0.4.24 and usb0 to use dhcp under the network manager applet.

When I remove usb ethernet device, ip link show only shows em1. Does this mean em1 maps to eth0? However as eth0 is no longer there (because the usb adapter has been removed), does that mean usb0 also maps to eth0?

My problem is that when I do an ifconfig, BOTH em1 and eth0 show an ip address of 10.0.4.24.

PS should this belong here or at serverfault?

edit: added requested output:

# more 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, and change only the value of the NAME= key.

# PCI device 0x8086:0x422b (iwlagn)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="24:77:03:74:85:98", ATTR{type}=="1", KERNEL=="wlan*", NAME="wlan0"

# USB device 0x0b95:0x7720 (usb)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:50:b6:50:b5:fc", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

---------------------

# more ifcfg-eth0 
DEVICE="eth0"
BOOTPROTO=none
#HWADDR="00:21:70:B9:4C:9F" # Commented by Clonezilla
NM_CONTROLLED="yes"
ONBOOT="yes"
TYPE="Ethernet"
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
IPADDR=10.0.4.24
PREFIX=24

-----------------------

# more ifcfg-usb0 
DEVICE="usb0"
NM_CONTROLLED="yes"
ONBOOT="no"
TYPE=Ethernet
BOOTPROTO=dhcp
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System usb0"
UUID=689ce77b-bfa1-c10b-19a2-eb3a89251128
HWADDR=02:80:37:EC:02:00
PEERDNS=yes
PEERROUTES=yes

-------------------------

# ifconfig
em1       Link encap:Ethernet  HWaddr D4:BE:D9:2B:D3:72  
          inet addr:10.0.4.24  Bcast:10.0.4.255  Mask:255.255.255.0
          inet6 addr: fe80::d6be:d9ff:fe2b:d372/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:120 errors:0 dropped:0 overruns:0 frame:0
          TX packets:57 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:11475 (11.2 KiB)  TX bytes:10552 (10.3 KiB)
          Interrupt:20 Memory:e6e00000-e6e20000 

eth0      Link encap:Ethernet  HWaddr 00:50:B6:50:B5:FC  
          inet addr:10.0.4.24  Bcast:10.0.4.255  Mask:255.255.255.0
          inet6 addr: fe80::250:b6ff:fe50:b5fc/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1000 errors:0 dropped:0 overruns:0 frame:0
          TX packets:473 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:87868 (85.8 KiB)  TX bytes:56643 (55.3 KiB)

Note there is no entry in ifconfig or ip link for usb0

Solution

Use NetworkManager, that is the way forward. It used to do weird things a while back, but that has been ironed out now. If you have some exotic setup, try to integrate it there. Only edit the files under /etc/sysconfig/network-scripts by hand as last resort.

Comments

[Krzysztof Księżyk]

Please paste here output of following files: /etc/udev/rules.d/70-persistent-net.rules /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-usb0

[A G]

hi, added the output to the bottom of the question