ip not reachable only in linux (guest)

[mkhm]

hello
how are you all ?
i have problem ,
i get subnet from hetzner /28
they routed it to my server ,,
the ip's is reachable when i setup it on windows guest !
or linux live cd's

also during installation to centos 6.3 when i add ip setting it's reachable but when it's finish & the system get up it's
tell me the guest ip is not reachable ,,

i disable all firewall's & add configure ip forwarding setting !!
i change the iso ,, also i try to install Ubuntu same thing !

i use kvm for virtualizing

there is any help ?

 

[mkhm]

hello ,,
there any configuration for network for Linux system ?
i used kvm to virtualizing & bridge for host - guest assign ip's
any help ?