openstack team mailing list archive

[Rangababu Chakravarthula <rbabu@xxxxxxxxxxxx>]

Couple of questions
a) How can we address the max 4096 vlan's problem if each user want's a VLAN
tagged network?
b) Docs says for each VLAN network, a dhcp server is started. How does it
work when we do livemigrate?

thanks

On Wed, Jul 20, 2011 at 11:56 PM, Thor Wolpert <thor@xxxxxxxxxx> wrote:

> 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@xxxxxxxxx> 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@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/
>>
>> _______________________________________________
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>>
>
>
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