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

[Andrew Dorozhkin]

11.09.2011 22:57, 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?
>
> Thanks for your help.
> Mike.
>
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You should not use 'PREFIX=...' parameter if you prefer static network 
settings
functionality provided by initscripts rather than NM daemon. I believe 
is is not honored
by ifup* scripts and is not documented by el6 deployment guide either. Use
'NETMASK=...' instead and then issue the command 'ifup eth0' to bring 
your NIC up
and running.