[CentOS] CentOS 6: ethernet "ifconfig up" failure

[Bernd Bartmann]

On Sun, Sep 11, 2011 at 8:57 PM, Michael D. Berger wrote:
> On my CentOS 6 partition of my laptop:
>
> First note that for this test, NetworkManager is not
> running because I did:
>   chkconfig --del NetworkManager
> and then rebooted.
>
> Here is my ifcfg-eth0:
>
> DEVICE="eth0"
> NM_CONTROLLED="no"
> ONBOOT=no
> HWADDR=xx:xx:xx:xx:xx:xx
> TYPE=Ethernet
> BOOTPROTO=none
> IPADDR=192.168.2.5
> PREFIX=24
> GATEWAY=192.168.2.1
> DNS1=192.168.2.1
> DNS2=192.168.2.1
> DEFROUTE=yes
> IPV4_FAILURE_FATAL=yes
> IPV6INIT=no
> NAME="System eth0"
> UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
>
> I reboot to level3, do startx (to KDE 4) then do:
> # ifconfig eth0 up
> # ping 192.168.9.1
> connect: Network is unreachable
>
> If I edit ifcfg-eth0 to set
>   ONBOOT=yes
> and reboot, I get a proper connection.
>
> So why is "ifconfig eth0 up" not connecting?

"ifconfig" is a low level tool that does not parse the config files
like ifcfg-eth0. You'll either have to use:

ifconfig eth0 192.168.2.5
route add default gw 192.168.2.1

or

ifup eth0

The latter one is a script that parses all the config files.

Best regards,
Bernd.