Virtual Machine routing On Ubuntu

Charles Curley charlescurley at
Thu Jun 17 21:15:43 MDT 2010

On Thu, 17 Jun 2010 19:45:50 -0600
Richard Esplin <richard-lists at> wrote:

> What virtualization software (hypervisor) are you using? VMWare,
> VirtualBox, KVM, Xen?


> How did you set up the NIC in the hypervisor? NAT vs bridged vs
> host-only?

It says here, "Forwarding: NAT to any physical device".

> In Virtualbox I set up two NICs, one as NAT and one as host-only in
> order to make my VM available to other VMs, the host, and enable
> access to the outside world while still protecting it from the host's
> physical network.

What's the difference between NAT and host-only?

I assume that in this context NAT means Network Address Translation,
i.e. the host acts as a firewall and does NATting.

The software I'm using is libvirt 0.7.0.

I also see that from a VM I can ping the host's virtual interface, i.e.
the IF on the virtual network. I can also ping its physical IF, which
is on a separate network.

> Richard
> On Thursday, June 17, 2010 18:32:17 Charles Curley
> <charlescurley at> wrote:
> > I have several VMs on a Ubuntu 9.10 host, and they have networking
> > set up. I can ssh in to them from the host, but not from other
> > machines, in spite of having the route set up correctly on the
> > other machines.
> > 
> > I also notice that I can get updates on the VMs (yum, apt, etc.) but
> > not web pages from the outside world. But I can get web pages from
> > the host.
> > 
> > So something is filtering the virtual network. What is it and how
> > do I control it?
> <snip>
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