IlyaZ,
First check out for /etc/resolv.conf;
as it should have either your router's ip in it or any global dns(public real static ip) in it.
Code:
e.g. nameserver 192.168.1.1
Second your network card should have router's ip acting as its gateway.
Code:
cat /etc/sysconfig/network-scripts/ifcfg-eth0
Even after first & second suggestions being OK; & you net is still not working, you got to move to third point..
Third
Check whether your firewall is working or not & stop if it is
Code:
service iptables status
service iptables stop