[CentOS-virt] Need Help with Xen Please

Brett Worth brett at worth.id.au
Fri Nov 28 05:12:26 UTC 2008

Jason Taylor wrote:

> Can anyone suggest what the next course of action would be? The server has a
> single physical NIC and 1 IP. Will I need to request an additional IP
> address to use with the new guest I create?


AFAIK you will need another IP address for the VM.  This can be done either via DHCP or
hard wired in the configuration file.

When you start the xend the python scripts rename your physical ethernet interface to from
eth0 something like peth0.  Then a software bridge is created (br0) and the peth0 device
is attached to one of its virtual ports.  Then one of the virtual ethernet devices (veth0)
is configured to have the same IP/netmask/broadcast etc as the peth0 device originally had
when it was eth0.  This interface is also attached to the br0 device.

>From then on your VM's interfaces are also attached to this br0 device.  Think of this
bridge as a switch.  The VM's network connection is totally external to the Dom0's network
interface so need to be treated as such.  With some scripting you could create another
bridge device (e.g. br1) and use either Dom0 or a VM as a masquerading gateway device but
that is left as an exercise for the reader. :-)


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