[Openstack-operators] [OpenStack-Operators][Neutron] Config options

Dan Wendlandt dan at nicira.com
Fri Aug 9 15:16:51 UTC 2013

Yeah, this basically comes down to what entity is going to be the
authoritative source of IP address assignment.  Quantum... errr, Neutron
assigns IP addresses when a new NIC is allocated, but unless you have
external logic to pull those IP address assignments out of Neutron (e.g.,
via the API) and into your corporate DHCP server, the DHCP response to the
VM will not match the one assigned by Neutron.

Another approach that is possible is to have an some logic outside of
OpenStack pick the MAC + IP address(es) to be used by a VM.  This logic
would then push this information to the DHCP server, and "push" it to
Neutron by creating a port with that MAC + IP on the desired network, and
then passing in that port-id when booting the VM.  This is the designed way
to bypass having Neutron allocate an IP from a pool on its own.

Making the Neutron IPAM more pluggable so that it could, for example,
interact with the corporate DHCP when allocating IPs for certain networks
is something that has been discussed and would be valuable, though I am not
personally aware of anything in progress on that end.


On Thu, Aug 8, 2013 at 7:39 PM, Lorin Hochstein <lorin at nimbisservices.com>wrote:

> Hi John:
> I don't think OpenStack supports an external DHCP server, because there's
> no mechanism for OpenStack to determine which IP addresses have been
> assigned to the instances. You could configure the OVS plugin in flat mode
> for each of the two physical networks, but you wouldn't know what the IP
> addresses were of the instances after they booted.
> Lorin
> On Sun, Aug 4, 2013 at 11:54 AM, John Griffith <
> john.griffith at solidfire.com> wrote:
>> Hey Everyone,
>> I have a specific use case that I'm trying to use in OpenStack.
>> My Compute Node has two public Nics (one for data/iscsi (10G) and one for
>> general public net access (1G)), both networks have their own DHCP server.
>>  Each compute node also has an additional 10G network for OpenSack
>> management.
>> Here's what I've been trying to get working:
>> * assign both public networks to the instances on boot
>> * utilize the corporate DHCP server to handle IP assignment and config
>> for both of those networks on the instance.
>> I have not been able to get this to work and was wondering if any Neutron
>> folks (or anybody else for that matter) had any tips on how to configure
>> this?
>> I'm using KVM/Libvirt with openvswitch, but I'm willing to change things
>> around if needed to make this work.
>> Thanks,
>> John
>> _______________________________________________
>> OpenStack-operators mailing list
>> OpenStack-operators at lists.openstack.org
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
> --
> Lorin Hochstein
> Lead Architect - Cloud Services
> Nimbis Services, Inc.
> www.nimbisservices.com
> _______________________________________________
> OpenStack-operators mailing list
> OpenStack-operators at lists.openstack.org
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Dan Wendlandt
Nicira, Inc: www.nicira.com
twitter: danwendlandt
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