Open Stack

Hi Wilence,

(for Juno), DHCP agent uses one subnet for a given network. (even if you
have multiple --dhcp enabled subnets on the same network).

check "neutron net-list" command. First subnet in given network will be
used as ip pool and new instance will get its ip from that pool via dhcp.
If you need to change subnet in instance launch step, you should use fixed
-ip when you create a new instance.

I do not think that you can do much in dashboard when you want to transfer
an instance from subnet1 to subnet2. However, you can use nova client-cli
to attach/detach interfaces to your instance. (Be careful, you need to
manually configure the second fixed-ip in your instance since
interface-attach can not do anything to configure newly added interface.
Just newly added device will available but not configured).

Erhan,




On Thu, Jan 15, 2015 at 9:46 AM, Wilence Yao <wilence.yao at gmail.com> wrote:

> Hi, All
>   I am new for openstack and focusing on networking. When I create a
> instance from dashboard, I can only chose a network for my instance. But
> in  my opinion, the instance should belong to one given subnet but not a
> network.
>   Then I read the nova manual. I found that a instance can boot with a
> fixed-ip from a nic. So , when my private network has two subnets(subnet1
> 10.0.0.0/24 and subnet2 10.0.1.0/24), the instance launched from
> dashboard was allocated to the  isubnet1 by default. How can I launch a
> instance and  allocatedit  to a subnet I chosen?  Should I allocate a fixed
> ip to the instance instead of dhcp?
> By the way, when I transfer a instance form subnet1 to subnet2, what can I
> do in dashboard?
> The test environment is devstack juno in ubuntu 14.04.
>
> Appreciate your help in advance.
>
> Thanks,
> Wilence
>
>
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