[openstack-dev] [Neutron] Use public IP address as instance fixed IP

Bao Wang bywang98 at gmail.com
Tue Aug 26 19:08:14 UTC 2014


Just want to clarify something. this public ip as private ip is only for
external facing interfaces on a set of VM instances. At the same time, the
majority of interfaces on hte same set of VM instances will not have public
ip and their subnets are isolated networks. Will this change your
conclusion when you mentioned "the gateway_external_network_id is left
blank for the L3 agent" ?


On Mon, Aug 25, 2014 at 1:07 AM, Kevin Benton <blak111 at gmail.com> wrote:

> I think this will depend on the deployment type for the L3 agent. If the
> gateway_external_network_id is left blank for the L3 agent, the external
> network is vlan tagged just like any regular network and doesn't have an
> independent bridge.[1] In that deployment scenario it should work fine.
>
>
> On Sun, Aug 24, 2014 at 9:30 AM, Mohammad Banikazemi <mb at us.ibm.com>
> wrote:
>
>>  Would this work? We used to have warnings in Neutron docs indicating
>> that instances should not be attached to external networks:
>> "It is important to understand that you should not attach the instance
>> to Ext-Net directly. Instead, you must use a floating IP to make it
>> accessible from the external network."
>>
>> In this particular case and with the OVS plugin, the traffic on the
>> external network which now hosts tenant VMs (on OpenStack compute nodes)
>> should get routed from the br-int to the external bridge br-ex using for
>> example the appropriate vlan id (what if external network does not use
>> vlan?) and then to the external network without doing the NATing. Would
>> this traffic go through the veth pair connecting the br-int and br-ex?
>>
>> Mohammad
>>
>> [image: Inactive hide details for Kevin Benton ---08/23/2014 01:37:28
>> AM---Yes, you should be able to create a shared/external network]Kevin
>> Benton ---08/23/2014 01:37:28 AM---Yes, you should be able to create a
>> shared/external network within Neutron to accomplish this.
>>
>> From: Kevin Benton <blak111 at gmail.com>
>> To: "OpenStack Development Mailing List (not for usage questions)" <
>> openstack-dev at lists.openstack.org>
>> Date: 08/23/2014 01:37 AM
>> Subject: Re: [openstack-dev] [Neutron] Use public IP address as instance
>> fixed IP
>> ------------------------------
>>
>>
>>
>> Yes, you should be able to create a shared/external network within
>> Neutron to accomplish this.
>>
>>
>> On Fri, Aug 22, 2014 at 7:25 AM, Bao Wang <*bywang98 at gmail.com*
>> <bywang98 at gmail.com>> wrote:
>>
>>    Thank you for your response. Could this be done naturally with
>>    Openstack neutron or have to be done manually outside neutron ?  As we are
>>    expecting to orchestrate hundreds of NFV with all similar network
>>    configuration, programmability is another key element.
>>
>>
>>    On Thu, Aug 21, 2014 at 3:52 PM, Kevin Benton <*blak111 at gmail.com*
>>    <blak111 at gmail.com>> wrote:
>>       Have you tried making the external network shared as well?
>>       Instances that need a private IP with NAT attach to an internal network and
>>       go through the router like normal. Instances that need a public IP without
>>       NAT would just attach directly to the external network.
>>
>>
>>       On Thu, Aug 21, 2014 at 7:06 AM, Bao Wang <*bywang98 at gmail.com*
>>       <bywang98 at gmail.com>> wrote:
>>          I have a very complex Openstack deployment for NFV. It could
>>          not be deployed as Flat. It will have a lot of isolated private networks.
>>          Some interfaces of a group VM instances will need bridged network with
>>          their fixed IP addresses to communicate with outside world while other
>>          interfaces from the same set of VM should keep isolated with real
>>          private/fixed IP addresses. What happen if we use public IP addresses
>>          directly as fixed IP on those interfaces ? Will this work with Openstack
>>          neutron networking ? Will Openstack do NAT automatically on those ?
>>
>>          Overall, the requirement is to use the fixed/public IP to
>>          communicate with outside directly on some interfaces of some VM instances
>>          while keeping others as private. The floating IP is not an option here
>>
>>          _______________________________________________
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>>
>>
>>       --
>>       Kevin Benton
>>
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>>
>>
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>
>
> --
> Kevin Benton
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