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Re: [Xen-users] can VDE be used in Xen



Simon Capstick wrote:
Shriram Rajagopalan wrote:
Ah, i forgot to mention an important constraint. Assuming that this garden of vlans is going to be created in a network of xen hosts, with one switch and (I dont have administrative access /any access at all to the switch), I would be looking for a switch emulator to do the vlan trunking
something on the lines of VDE, Serval , etc .

Have you or anybody for that matter had any experience with such software switch emulators (Serval sounds interesting)

Simon Capstick wrote:
RumbelStelskin wrote:
yes, but this arrangement would create a vlan inside a single host (or
am i wrong?)..
what if i want to vlanify domUs in different hosts (hosts in different
subnets too)?
and with the added complexity of several such disparate vlans in this
network of xen hosts


Simon Capstick wrote:
RumbelStelskin wrote:
virtual distributed ethernet


Todd Deshane wrote:
what is VDE?

On Jan 29, 2008 2:14 AM, RumbelStelskin <shriram@xxxxxxxxxxx <mailto:shriram@xxxxxxxxxxx>> wrote:

    i have spent the last 5 hours searching for some
    post/blog/experience on
    VDE Xen combo. but to no avail.

    VDE seems to be popular with KVM and other non virtualized
    environments
. Are there ways to use it with Xen, i mean, transparently connect a set of DomUs in different physical hosts in different networks , to
    form one virtual network?

If this cannot be done at Dom0 side, it always can be done at the DomU
    side, where the domu plugs into a vde switch. But are there any
    ballpark
    stats on the performance drops?

to put things in a nut shell, I am looking for some decent solution (with acceptable levels of performance loss) to form a virtual network of DomUs that are spread across physical machines, across physical
    networks (some behind nats/firewalls).
    is vlan the way to go?how?

    thanks
    r


This is how I would go about it:
Use vconfig on Dom0 to create a virtual interface on a VLAN, e.g. eth0.1. Then you would edit the Xen config to use that interface rather than the default eth0, in bridge mode of course (the default?). Do the same on all your Dom0s and you have a shared DomU network. For security you should restrict which ports on your switch can use your VLAN ID, i.e. the ones with Xen servers! You will then have to decide how to connect the VLAN to the outside world, via a DomU with acting as a router or via a physical router on your network.

Simon


The Xen created network bridge attached to the VLAN interface on Dom0 (not eth0) sends the appropriate traffic out to your physical network switch. It is my understanding that the VLAN interface is simply tagging packets and then sending them on over the specified physical interface (and receiving the correctly VLAN tagged packets too). Assuming you have set-up your switch correctly and other Dom0s with the same config then they should be able to communicate.

Of course reality may bite, and you may find problems with VLANs and Xen as discussed in posts in the list archive. But I assume the problems are now gone, or there are workarounds.

Simon


The only (secure) way I can think of is to set-up a Linux VPN between all the Dom0s in a mesh arrangement. Very CPU intensive I would imagine.

It would be much better to get hold of a physical switch you can manage.

Alternatively cable directly between Dom0s using cross-over cables, lots of NICs and some routing on the Dom0s (not a nice solution).

Simon


I should add that I haven't used Serval [1], but it does look interesting.

Simon
[1] http://community.igalia.com/twiki/bin/view/Serval/WebOverview


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