You _can_ do NAT.

Set up a  different libvirt network on each machine, like this;
10.128.80.65 will have a libvirt network 192.168.65.0/24
10.128.80.66 will have a libvirt network 192.168.66.0/24

Set up each of these networks as routed networks.

Now set up routing/iptables rules on each host to send traffic to each other, and NAT into the internal routed network

On 31/10/12 01:46, libvirt-users-request@redhat.com wrote:

Message: 1
Date: Tue, 30 Oct 2012 07:10:55 +0000
From: ??<zhang_zhang@live.com>
To:<libvirt-users@redhat.com>
Subject: [libvirt-users] Can VMs on different machines communicate
        with each other without IP?
Message-ID:<BLU172-W4666B32A6C9C8E75734C67FC620@phx.gbl>
Content-Type: text/plain; charset="gb2312"


Dear all,
      I confront a somehow strange situation:
      I have two machines configured with ip 10.128.80.65 and 10.128.80.66 respectively. Each has several VMs running on it. The problem is that I have no more ip ( such as 10.128.80.67...) to allocate to VMs, but VMs need to communicate with each other even when they are on different machines.
      Two network options exist: NAT and bridge.
      1) NAT
          But VMs on different machine cannot communicate with each other.
      2)bridge
          But there is no more ip for vm to be bridged to host machine.
      Is there any other way to work around this problem?


many thanks!