hello Ubuntu Community

I'm having a problem I installed a New Ubuntu Server 12.04 with 2 network cards, One with a static public address and one with a private address.

iface eth0 inet static
address xxx.xxx.xxx.xxx
gateway xxx.xxx.xxx.xxx
dns-nameservers xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx

iface eth1 inet static
dns-search example.com

I have internet, access with the Public IP.
The problem is that I cant do ping to another network (ex. but I can to my computer or inside the network, either can't do ping from another network to my server.

I really don't know the whats the problem, maybe someone can help Pls.

Thank you