RE: [Xen-devel] Xend vnet support to be removed

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

Based on the description from your documentation, it sounds like the
guts of vnets could be done with 802.1q vlan trunking and bridging. No
extra code required. I'm already doing this now, where each xen server
has two physical interfaces (one for AoE, and one for domu network
access). I can provide some more information on 802.1q vlan trunking if
anyone is interested.

I'm basing all of my knowledge of vnets on a brief skim of the
documentation in your email below, so feel free to enlighten me as to
why they are different :)

Thanks

James

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Mike Wray
> Sent: Tuesday, 13 December 2005 00:48
> To: Ewan Mellor
> Cc: Xen-devel
> Subject: Re: [Xen-devel] Xend vnet support to be removed
> 
> Ewan Mellor wrote:
> > On Mon, Dec 12, 2005 at 08:45:00AM +0000, Mike Wray wrote:
> >
> >
> >>Ewan Mellor wrote:
> >>
> >>>Unless someone speaks up, Xend vnet support will be removed.  It is
> broken,
> >>>unused, and unloved (as far as I know).  This is the xm vnet-list,
> >>>vnet-create, and vnet-delete commands, as well as all the Xend
support
> >>>behind
> >>>that (XendVnet.py, SrvVnetDir.py, plus plumbing in xm/main.py and
> >>>XendClient.py).
> >>>
> >>>Cheers,
> >>>
> >>>Ewan.
> >>
> >>As the developer of the vnet count I'm speaking up for this code.
> >>As far as I am aware it is neither broken nor unused, and I
> >>have recently submitted patches to this list updating the code.
> >>The code is in active development and I will be continuing to
maintain
> it.
> >>So please don't remove it.
> >
> >
> > That's fine.  It seems like there are a number of people using it or
> wishing
> > to, so it will stay in place.
> >
> > I asked because there was recently an effort to bring the
documentation
> up to
> > date, by various members of the Xen community, and yet the
documentation
> for
> > Xen 3.0 went out with no mention of the vnet support, because no-one
> seemed to
> > know how to use it properly.
> >
> > Perhaps you could write a few lines for us to go into the user
> documentation?
> > A number of people have said that that the vnet support is useful,
so it
> would
> > be good if we could get it documented, and spread the news!
> >
> > BTW, you don't have any patches unapplied and outstanding, do you?
If
> so,
> > then now would be a good time to resend them, because they've been
> missed if
> > so!
> >
> > Thanks,
> >
> > Ewan.
> 
> I think all the patches I've sent so far have been applied - I've got
> some more changes I'm working on, but they're not quite ready to post
> yet.
> 
> There's some brief documentation below (extracted from the doc
directory
> in the
> vnet source).  What format would you prefer for more extensive
> documentation?
> 
> 0) Introduction
> ---------------
> 
> Vnets provide virtual private LANs for virtual machines.
> This is done using bridging and multipoint tunneling. A virtual
interface
> on a vnet can only see other interfaces on the same vnet - it cannot
> see the real network, and the real network cannot see it either.
> 
> Virtual interfaces on the same vnet can be on the same machine
> or on different machines, they can still talk. The hosting machines
> can even be on different subnets if you run vnetd to forward,
> or have multicast routing enabled.
> 
> 
> 1) Installing vnet support
> --------------------------
> 
> Assuming the code has been installed (make install in the parent
> directory),
> configure xend to use 'network-vnet' instead of the default 'network'
to
> start up networking. This just loads the vnet module when networking
> starts.
> 
> In /etc/xend/xend-config.sxp:
> 
> Configure the network script:
> 
> (network-script        network-vnet)
> 
> Restart xend.
> 
> Alternatively insert the vnet module using vnet-insert,
> preferably before xend starts.
> 
> 2) Creating vnets
> -----------------
> 
> Xend already implements commands to add/remove vnets and
> bridge to them. To add a vnet use
> 
> xm vnet-create <vnet config file>
> 
> For example, if vnet97.sxp contains:
> 
> (vnet (id 97) (bridge vnet97) (vnetif vnif97) (security none))
> 
> do
> 
> xm vnet-create vnet97.sxp
> 
> This will define a vnet with id 97 and no security. The bridge for the
> vnet is called vnet97 and the virtual interface for it is vnif97.
> To add an interface on a vm to this vnet simply set its bridge to
vnet97
> in its configuration.
> 
> In Python:
> 
> vif="bridge=vnet97"
> 
> In sxp:
> 
> (dev (vif (mac aa:00:00:01:02:03) (bridge vnet97)))
> 
> At the moment you will also have to reduce the MTU of the
corresponding
> device in the domain (because of the tunneling). For example, for eth0
use
> 
> ifconfig eth0 mtu 1400
> 
> or, better, put
> 
> MTU=1400
> 
> in /etc/sysconfig/network-scripts/ifcfg-eth0. You may also have to
change
> or remove
> cached config files for eth0 under /etc/sysconfig/networking.
> 
> Once configured, vnets are persistent in the xend database.
> To remove a vnet use
> 
> xm vnet-delete <vnet id>
> 
> To list vnets use
> 
> xm vnet-list
> 
> To get information on one or more vnet ids use
> 
> xm vnet-list <vnet id>...
> 
> 3) Troubleshooting
> ------------------
> 
> The vnet module should appear in 'lsmod'.
> If a vnet has been configured it should appear in the output of 'xm
vnet-
> list'.
> Its bridge and interface should appear in 'ifconfig'.
> It should also show in 'brctl show', with its attached interfaces.
> 
> You can 'see into' a vnet from dom0 if you put an IP address on the
> bridge.
> For example, if you have vnet97 with a vm with ip addr 10.0.0.12 on
it,
> then
> 
> ifconfig vnet97 10.0.0.20 up
> 
> should let you ping 10.0.0.12 via the vnet97 bridge.
> 
> 
> Mike
> 
> 
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