[neutron] Shared tenant network allow duplicate IP's?

Dan Sneddon dsneddon at redhat.com
Wed Feb 26 21:26:43 UTC 2020

On Wed, Feb 26, 2020 at 11:49 AM Adam Peacock <alawson at aqorn.com> wrote:

> Hey folks,
> So I caught wind from a friend/colleague that allowing duplicate IP's in
> each tenant was now only achievable by creating a separate tenant
> network+subnet and assigning them separately to each individual tenant.
> This doesn't seem right to me and it doesn't scale.
> *Looking for this:*
>    - tenant-network-id = abc (shared)
>       - tenant1
>          - vm1:
>       - tenant2
>          - vm1:
> Am I missing something and this setup is no longer supported?
> I hope I'm wrong but I can't find documentation that speaks to this
> specifically so would appreciate a link if anyone has it handy.
> Thanks!
> //adam
> *Adam Peacock*
> Principal Architect
> Office: +1-916-794-5706

That has never been supported. It is not feasible to have two VMs on the
same network+subnet that have the same IP, even if they are owned by
different tenants. That isn't a Neutron limitation, that's a limitation of
IP-over-Ethernet that applies to all networks.

Think of the non-virtualized equivalent, if you had a physical network
subnet with two computers using the same IP address there would be a
conflict, even if one computer was owned by Alice and the other computer
was owned by Bob. There is no way to make that work in a virtualized cloud
environment unless the two tenants are using different network subnets.

Dan Sneddon         |  Senior Principal Software Engineer
dsneddon at redhat.com |  redhat.com/cloud
dsneddon:irc        |  @dxs:twitter
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