Re: [Xen-users] what creates the veth* devices?

[Chris Stromsoe <cbs@xxxxxxxxxxxx>]

On Fri, 6 Jul 2007, Mark Williamson wrote:

> > What creates the veth* devices and is it necessary to have them in 
> > order to have correct / functional networking?
> What makes you think you should have them?  They were present in some 
> versions of Xen and not in others (I regret I can't remember how the 
> network was set up in 3.0.3).
Nothing makes me think that I should have them.  If I use "network-bridge" 
they show up.  Looking at the network-bridge script, it wasn't immediately 
obvious (or even not so immediately obvious) what creates the veth 
devices.  There doesn't appear to be any documentation online (that I 
could find at least) saying what creates them or whether or not they're 
required.
> > I'm using Xen 3.0.3 on Debian Etch.  I have my dom0 networking being built
> > using standard Debian configuration in /etc/network/interfaces.
> > xend-config.sxp is set to use
> >
> > (network-script network-dummy)
> >
> > My domU configurations are set with
> >
> > vif = [ 'type=ioemu, bridge=xenbr772' ]
> >
> > Everything seems to be working as near as I can tell, except that I 
> > don't have any veth* devices.  My domUs all have a vif device that 
> > shows up as part of the correct bridge when the domU starts up.  Do I 
> > need those?
> The vif devices are a representation of what the netback driver is up 
> to. Logically, each vif device in dom0 is connected via "virtual 
> crossover" to a vif in a guest.  Because of this, you need them to be 
> up, or you won't be able to access the guest's network card (and vice 
> versa).
Sorry, that was really bad writing on my part:  that bit was meant to be a 
further explanation of the first sentence of my email, explaining that my 
configuration without the veth* devices seems to be working and has the 
right bridges and vif* devices.
The question was actually to find out if I need (for whatever reason) the 
veth* devices.  I don't appear to need them, but as I said there isn't a 
lot of documentation for non-default setups, and most of what I've been 
able to find looks like helpful hints for modifying the default setup.

That said, do I need the veth* devices?  Is there a downside to not having 
them?  Am I missing out on anything by configuring the bridge setup using 
the normal Debian /etc/network/interfaces in dom0 instead of trying to 
modify network-bridge to work with bonded interfaces and vlans?



-Chris

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