What happens if you set up your OS (in my case Fedora 16), configure your network card as it should be : IP, network, gateway..
Turn off all that (in the testing phase) should be turned off :
iptables, ip6tables, SELinux
Server is pinging itself, but nobody can ping him, and he can not ping his own gateway.
In this (dismal) state of affairs, you should try Ethereal, or its modern brother Wireshark, to catch packages on the network. If packages are there, but ping is still not working, talk to your network gay/girl. It may be that your network is NOT a ordinary network, but is configured as the VLAN trunk mode, so your ordinary LAN configuration will simply not work.
There are two ways to do this, but I will here present only one, since I have tried it, and it works.
In my case it looks like this :
# cd /etc/sysconfig/network-scripts
# cp ifcfg-em1 ifcfg-vlan2 since it is in VLAN2 we call it that
We have also to change the configuration of the original LAN card :
DEVICE=”em1″ name of the network card
ONBOOT=no we do not want it to start with the system, VLAN2 should
IPADDR0=0.0.0.0 yes, it should be lake this!
And the changes in the new VLAN2 card :
IPADDR0=10.11.12.13 IP address which we want our server to have
After this, restart networking service, and test the whole thing.