Re: [Xen-users] Re: Will pv-ops dom0-patched kernel be eventually merged into Linus Torvalds' mainline Linux kernel tree?

[Freddie Cash <fjwcash@xxxxxxxxx>]

On Mon, Nov 9, 2009 at 10:27 PM, Mr. Teo En Ming (Zhang Enming)
<space.time.universe@xxxxxxxxx> wrote:
> One of the reasons why I prefer Xen over KVM is because of networking.
>
> I have a Gigabit network card on my Intel DQ45CB motherboard. I don't see a
> need to install an additional network card on my motherboard as PCI and PCIe
> expansion slots are limited.
>
> In the case of Xen, the physical network interface in my host operating
> system (dom0) and the virtual network interfaces in my guest operating
> systems (domU) can be added to the same ethernet bridge on the host OS. This
> implies that my host and virtual machines will have IP addresses in the same
> subnet. Moreover, if I do not want to configure static IP addresses, my
> virtual machines (VMs) can obtain IP adddresses from the DHCP server on
> commercial routers like Linksys, D-Link, Netgear, etc, similar to the way
> the physical network card on the host obtaining its IP address from the same
> router.
>
> But, for the case of KVM, I need to setup an internal network for my guests.

Bzzzt!  Incorrect.  KVM supports the exact same networking methods as
Xen.  In fact, it's a lot simpler to setup bridged networking in KVM
then in Xen, as KVM uses the default network configuration scripts of
the host OS.

In Debian, it's as simple as editing /etc/network/interfaces, creating
the bridge configuration in there, and then pointing /etc/kvm/kvm-ifup
to use that bridge.

Xen 3.0 used to be this simple, and the bridge device was separate
from the physical interface.  Then in Xen 3.2 everything changed, and
it became a royal pain to configure as the physical interface was
renamed, and the first interface with an IP was used as the bridge
device, completely breaking setups where you have a management
interface with an IP, and separate interfaces for the bridge(s).
(Yes, I know it's possible to work around this, but it broke existing
setups, and changed things for no good reason.)

-- 
Freddie Cash
fjwcash@xxxxxxxxx

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