[ovirt-users] About NAT in libvirt default virbr0, it cannot reach LAN of host.

Some users of mine are complaining about NAT in oVirt. They said that vmware's NAT can reach LAN of host like 192.168.1.0/24, but NAT(I use extnet.py in hooks, ie. 192.168.122.0/24) in oVirt cannot do that. I've tried kinds of network in virt-manager like route, nat, isolated. What's the difference between libvirt's NAT and VMWare's NAT? What should I do to make libvirt's NAT reach LAN of the host?