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

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?


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