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That was a great explanation, thanks!

There is also a limit of 12 bits in the 802.1Q protocol, effectively setting
the max to 4096 vlans

I so look forward to having that kind of problem :)!

On Wed, Jul 20, 2011 at 9:26 PM, Jeff Kramer <jeffkramer at gmail.com> wrote:

> As I understand it, you can setup the tags in the switch first if you
> want, but you don't need to.  You will create VLAN tags in the Nova
> database as you create networks with 'nova-manage network create ...',
> and those will be assigned to users on a first-come first-serve basis.
>  When a user creates their first node nova assigns them an unused
> network which has a unique VLAN tag.  This tag is passed to
> nova-compute when your instance is started, and it feeds that VLAN tag
> into KVM which uses it for all network traffic in a way that's
> transparent to the guest OS.  When the guest talks to the network it
> uses that VLAN tag, which the nova-network node is also listening on.
>
> As long as your switch supports host-tagged VLANs (802.1Q), you don't
> have to create the tags in the switch before you use them.  You could
> setup all your VLANs before, someone else may have more experience
> with that.
>
> One wrinkle is that many switches have a set number of tagged VLANs
> they can support, for instance the HP V1810-24G switch that I'm using
> supports 64 tagged VLANs, which means my Nova cluster can only have 64
> different networks (or 64 different users).  The next model up
> supports 256, etc.  I assume that if you go over this number your
> network traffic will start dropping and weird things will happen.
>
> Your switch's management IPs should probably be in an address space
> that doesn't conflict with what you're assigning with nova.  If you're
> using 10.x.x.x for Nova you could put the switch on 192.168.x.x.  You
> probably shouldn't be touching the switch from a Nova guest, since the
> time you'll want to be fiddling with it will be when your Nova cluster
> is crashing or otherwise broken.
>
>
> On Wed, Jul 20, 2011 at 10:43 PM, tianyi wang <wangcity at gmail.com> wrote:
> > Hi, all
> >
> >
> >     If use VLAN mode, it's need setting VLAN in switch's NOS first?
> > And then the setting VLAN in nova controller node?
> >
> > Now, the switch's IP is 192.168.0.234 and the gateway ip address is
> > 192.168.0.1 ( in switch web management interface), should I change the
> > switch  IP and gateway to 10.0.0.x ?
> >
> > In VLAN mode, what's the relationship tween the controller node's VLAN
> > management and switch's NOS VLAN management?
> >
> > thanks
> >
> >
> > alex
> >
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>
>
>
> --
> Jeff Kramer
> jeffkramer at gmail.com
> http://www.jeffkramer.org/
>
> _______________________________________________
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