Re: [Xen-users] Is this simplest path to subnets?

[John Morris <jman@xxxxxxxxxxx>]

The way I do it these days is just to set up a bridge outside xen with 
an ip address.  You don't need a network script in the xen config that 
way.  Then you can just add your domU interfaces to the bridge, and 
route between the bridge device and the physical device.
   John


Valter Douglas Lisbôa Jr. wrote:
> On Tuesday 19 February 2008 23:55:58 Stephan Seitz wrote:
>   
> > I did a similar setup by
> >
> > modprobe dummy
> > ifconfig dummy0 up
> >
> > and using a wrapper script for network-bridge to setup bridges
> > for eth0 and dummy0 (i also wanted eth0 bridged)
> >
> >     
> I do this, in a very similar wrapping you use. 
>
>   
> > this generally works, but i suspect this bridge as reason for
> > dom0 freeze on heavy net-io... maybe someone can confirm problems
> > with dummy bridges?
> >     
> But I don't find any freeze problems with high I/O, and believe me I have four 
> on productions server with great load on network and I trying various 
> benchmarking tests between VMs and copy huge amount of data between them. I 
> already stop a low cost Encore switch in one of this tests ;-)
>   
> > Tom Horsley schrieb:
> >     
> > > I've been making my brain hurt by reading up on xen networking,
> > > and I wonder if I finally understand the simplest path to getting
> > > my virtual machines on a separate subnet:
> > >       
> I create a config similar a level 2 bastion firewall with a dmz. The two 
> gateways to server the edges (one to LAN and other to WAN) has two separate 
> bridges each like the diagram bellow
> WAN---(Brdige WAN)---[VM1]---(Bridge DMZ)---[VM2]---(Bridge LAN)---LAN
>
> The VMs side connected on physical interface (WAN and LAN) has the normal 
> config. The side on bridge DMZ has any number of VMs limited by the hardware 
> attached with dummy if. I have some delay here, but it's not noticiable. 
>
>   
> > > In the physical world, if I hook two subnets to a linux box with
> > > two ethernet cards, all I need is some routing commands on that
> > > gateway box, and the subnets can talk to one another.
> > >       
> Yes I did this too.
>
>   
> > > In the virtual world, I'm thinking the simplest to understand
> > > equivalent is to create a dummy ethernet interface in
> > > /etc/network/interfaces so it gets brought up as soon as the
> > > Dom0 boots.
> > >
> > > Then tell the standard network-bridge script to use the dummy
> > > interface as the "netdev", but other than that, use the default
> > > bridge scripts (including the default vif-bridge).
> > >
> > > If I'm even close to understanding this now, the original physical
> > > eth0 on the Dom0 will be completely left alone by xen, and if I setup
> > > static routes between it and the dummy ehternet, then my physical
> > > and virtual subnets will be able to talk just like in the
> > > two physical subnet case.
> > >
> > > Does this make any sense at all? Am I pointing in a direction
> > > that might work?
> > >
> > > Thanks for any insight you can provide.
> > >
> > > (I'm not interested in firewalls and NAT and that other brain
> > > exploding nonsense yet, I just want to see the simplest case
> > > working first :-).
> > >       
> You in the right way. I almost explode my brain in the first time, and I stay 
> one week inside this problem. But now, its appear to be all right.
>   
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> > >       
>
>
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