Open Stack

Hi Jaison,

This is an issue that the Neutron team is aware. They will likely be
addressing this (at some point) but your understanding aligns with my own.
So, public IPV4 usage is a well known, well documented issue and DVR / HA
exacerbates it.

On Tue, Apr 26, 2016 at 1:33 AM, Jaison Peter <urotrip2 at gmail.com> wrote:

> Hi all,
>
> I  was working in an openstack project to build a small to medium level
> public cloud on the top of openstack. We are researching lot more about
> scalable large openstack deployments and planning our design accordingly.
> Initially we will be having 50+ compute nodes and planning to grow up to
> 200 compute nodes in an year by migrating the existing clients to new
> platform.
>
> I have many concerns about the scaling and right choices , since openstack
> is offering lot of choices and flexibility, especially in networking
> side.Our major challenge was choosing between simplicity and performance
> offered by Linux bridge and features and DVR offered by OVS.  We decided to
> go with OVS, though some were suggesting like OVS is slow in large
> deployments. But the distributed L3 agents and bandwidth offered by DVR
> inclined us towards OVS. Is it a better decision?
>
> But one of the major drawback we are seeing with DVR is the public IP
> consumption. If we have 100 clients and 1 VM per client , eventually
> there will be 100 tenants and 100 routers. Since its a public cloud, we
> have to offer public IP for each VM. In DVR mode, fip name space in compute
> will be consuming one public IP and if 100 VMs are running among 20
> computes, then total 20 public IPs will be used among computes. And a
> router SNAT name space will be created for each tenant router(Total 100)
> and each of it will be consuming 1 public  IP and so total 100 public IPs
> will be consumed by central SNAT name spaces. So total 100 + 20 = 120
> public IPs will be used by openstack components and  100 will be used as
> floating IPs (1:1 NAT) by VMs. So we need 220 public IPs for providing
> dedicated public IPs for 100 VMs !! Anything wrong with our calculation?
>
> From our point of  view 120 IPs used by openstack components in our case
> (providing 1:1 NAT for every VM) is wastage of IPs and no any role in
> network traffic. Centrallized SNAT is useful , if the client is opting for
> VPC like in AWS and he is not attaching floating IPs to all instances in
> his VPC.
>
> So is there any option while creating DVR router to avoid creating central
> SNAT name space in controller node ? So that we can save 100 public IPs in
> the above scenario.
>
>
>
>
>
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