openstack team mailing list archive

[Dan Wendlandt <dan@xxxxxxxxxx>]

On Mon, Jul 25, 2011 at 3:08 PM, Rangababu Chakravarthula <
rbabu@xxxxxxxxxxxx> wrote:

> Thank you Dan. Response below.
>
> On Mon, Jul 25, 2011 at 11:36 AM, Dan Wendlandt <dan@xxxxxxxxxx> wrote:
>
>> Hi Rangababu,
>>
>> On Sat, Jul 23, 2011 at 12:58 PM, Rangababu Chakravarthula <
>> rbabu@xxxxxxxxxxxx> wrote:
>>
>>> Couple of questions
>>> a) How can we address the max 4096 vlan's problem if each user want's a
>>> VLAN tagged network?
>>>
>>
>> Currently, the notion of a VLAN is pretty central to the nova networking
>> code.
>>
>> Removing this restriction and enabling more scalable network isolation
>> mechanisms is one of the motivations for the Quantum virtual network service
>> (see: http://wiki.openstack.org/Quantum).
>>
>>
>
>>
>>> b) Docs says for each VLAN network, a dhcp server is started. How does it
>>> work when we do livemigrate?
>>>
>>
>> Before and after the live migrate, the VM interface should be plugged into
>> the same ethernet broadcast domain, so everything will continue to work
>> (i.e., addresses from old DHCP lease remains valid, future DHCP requests
>> will go to the same DHCP server).
>>
>> >>>>That answers my question. However if the host on which dnsmasq is
> running needs to go down for maintenance, it should hand over the dhcp
> responsibility to another compute node. Am I right?
>

Vish actually did a great write-up on this recently:
http://unchainyourbrain.com/openstack/13-networking-in-nova



>
>
>> Dan
>>
>>
>>
>>
>>>
>>> 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
>>>>> >
>>>>> > _______________________________________________
>>>>> > Mailing list: https://launchpad.net/~openstack
>>>>> > Post to     : openstack@xxxxxxxxxxxxxxxxxxx
>>>>> > Unsubscribe : https://launchpad.net/~openstack
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>>>>> >
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Jeff Kramer
>>>>> jeffkramer@xxxxxxxxx
>>>>> http://www.jeffkramer.org/
>>>>>
>>>>> _______________________________________________
>>>>> Mailing list: https://launchpad.net/~openstack
>>>>> Post to     : openstack@xxxxxxxxxxxxxxxxxxx
>>>>> Unsubscribe : https://launchpad.net/~openstack
>>>>> More help   : https://help.launchpad.net/ListHelp
>>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>> Post to     : openstack@xxxxxxxxxxxxxxxxxxx
>>>> Unsubscribe : https://launchpad.net/~openstack
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>>>>
>>>>
>>>
>>> _______________________________________________
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>>>
>>>
>>
>>
>> --
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Dan Wendlandt
>> Nicira Networks, Inc.
>> www.nicira.com | www.openvswitch.org
>> Sr. Product Manager
>> cell: 650-906-2650
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>>
>


-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dan Wendlandt
Nicira Networks, Inc.
www.nicira.com | www.openvswitch.org
Sr. Product Manager
cell: 650-906-2650
~~~~~~~~~~~~~~~~~~~~~~~~~~~