openstack team mailing list archive

[Jeff Kramer <jeffkramer@xxxxxxxxx>]

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@xxxxxxxxx> 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@xxxxxxxxx
http://www.jeffkramer.org/