[all variants] Internet not working on Virt-manager guest

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http://ubuntuforums.org – Hi I am using Ubuntu 12.04. My laptop gets internet from a wireless router which is connected to a modem. I already have a full working Centos 6 vm with Virtualbox which has working internet. I am trying to use Centos 6 in a Virt-manager virtual machine with KVM. I have installed created and installed Centos 6 with Virt-manager and everything seems to be working except the internet. On both Virtualbox and Virt-manager I am using NAT but internet is only working on Virtualbox. I have tried selecting different NAT device models but internet still didn't work. I have attached screenshot (Hardware)