On 03/03/2025 13:50, Ricardo Cano wrote:
> Hello openstack-discuss,
>
> With the removal of the linuxbridge mechanism driver, has anyone
> successfully completed an in-place migrationfrom LinuxBridge to OVN?
> I did come across this
> https://www.jimmdenton.com/migrating-lxb-to-ovn/ and that looks good
> as a one-shoit while biting the bullet and taking a full outage.
> However, I was wondering if it was possible to run lxb and ovn
> side-by-side and cut them over, say one network at a time.
>
> This particular deployment was stood up using openstack-ansible back
> in the rocky days (now running antelope) and it appears that openstack
> ansible's default was lxb up until Zed.

that is likely because the official default backend of neutron was Linux
bridge

in the install guide since it creation until it was marked experimental
by neutron

our devstack ci jobs defaulted to ovs for most of openstack lifetime but

ovs only became the offical default backend when linux bridge was marked
experimental

https://docs.openstack.org/neutron/latest/install/controller-install-ubuntu.html#finalize-installation

ovn is still not the default in the docs or in most installers even if
that is what we use in the devstack jobs
by default.

its an add on alretrnive procedure for "advanced users only"

https://docs.openstack.org/neutron/latest/install/ovn/manual_install.html

so openstack-ansibel was jsut followign the documented defautl backend.

kolla, devstack and tripleo diverged from that.

>
> Any suggestions or recommendations on the best path forward?
>
> Also, will the dynamic routing agent work with ovn

i believe ovn does DVR differently without a requirement form the agent.

i.e. if the vm has a floating ip i belive ovn can route that traffic
locally to the internet form the compute without

needing to use a central gateway but ill admit i could be missremebering
that i have not looked at it in detail in a number of years.

https://docs.openstack.org/neutron/latest/ovn/gaps.html

"""

*

    Floating IP Port Forwarding in provider networks and with
    distributed routing

    Currently, when provider network types like |vlan| or |flat| are
    plugged to a router as internal networks while the
    |enable_distributed_floating_ip| configuration option is enabled,
    Floating IP port forwardings which are using such router will not
    work properly. Due to an incompatible setting of the router to make
    traffic in the vlan/flat networks to be distributed but port
    forwardings are always centralized in ML2/OVN backend. This is being
    reported in [11]
    <https://docs.openstack.org/neutron/latest/ovn/gaps.html#id23>.

[11] https://bugs.launchpad.net/neutron/+bug/2028846
<https://bugs.launchpad.net/neutron/+bug/2028846>

"""

>