No.

It seems to me this package had never got installed but in 4.2.x OVN external network provider worked.

The environment was created at beginning 2017 with 4.0.6 and then gradually updated, now at 4.3.2.

OVN originally installed when in 4.1.0 with the manual way before official inclusion in engine-setup

[root@ov300 ~]# rpm -q vdsm-hook-openstacknet
package vdsm-hook-openstacknet is not installed
[root@ov300 ~]# 

[root@ov300 ~]# ll -rt /var/log/yum.log*
-rw-------. 1 root root 63893 Sep 29  2017 /var/log/yum.log-20180101
-rw-------. 1 root root 13840 Feb  9  2018 /var/log/yum.log-20180326
-rw-------. 1 root root 43106 Nov 22 11:47 /var/log/yum.log-20190101
-rw-------. 1 root root 38473 Mar  5 13:46 /var/log/yum.log-20190306
-rw-------. 1 root root  5018 Mar 22 14:11 /var/log/yum.log
[root@ov300 ~]# 

[root@ov300 ~]# grep vdsm-hook-openstacknet /var/log/yum.log*
[root@ov300 ~]#

And the same for the other two hosts

I can confirm that if I install that package (no vdsm restart):

Installing:
 vdsm-hook-openstacknet              noarch              4.30.11-1.el7               ovirt-4.3               14 k

The VM with OVN network card on ovn192 is able to boot now and I have the vnet1 interface on ov300

[root@ov300 ~]# ovs-vsctl show
f1a41e9c-16fb-4aa2-a386-2f366ade4d3c
    Bridge br-int
        fail_mode: secure
        Port br-int
            Interface br-int
                type: internal
        Port "ovn-b8872a-0"
            Interface "ovn-b8872a-0"
                type: geneve
                options: {csum="true", key=flow, remote_ip="10.4.192.34"}
        Port "ovn-1dce5b-0"
            Interface "ovn-1dce5b-0"
                type: geneve
                options: {csum="true", key=flow, remote_ip="10.4.192.32"}
        Port "vnet1"
            Interface "vnet1"
    ovs_version: "2.10.1"
[root@ov300 ~]#

[root@ovmgr1 ~]# ovn-sbctl show
Chassis "ddecf0da-4708-4f93-958b-6af365a5eeca"
    hostname: "ov300.datacenter.polimi.it"
    Encap geneve
        ip: "10.4.192.33"
        options: {csum="true"}
    Port_Binding "84c78095-744c-4415-805f-5f739af3d4d3"
Chassis "1dce5b7c-a9fc-4ddb-99b4-e2c9e0fa54c5"
    hostname: "ov200.datacenter.polimi.it"
    Encap geneve
        ip: "10.4.192.32"
        options: {csum="true"}
Chassis "b8872ab5-4606-4a79-b77d-9d956a18d349"
    hostname: "ov301.datacenter.polimi.it"
    Encap geneve
        ip: "10.4.192.34"
        options: {csum="true"}
[root@ovmgr1 ~]#

And on engine:

[root@ovmgr1 ~]# ovn-nbctl show
switch fc2fc4e8-ff71-4ec3-ba03-536a870cd483 (ovirt-ovn192-1e252228-ade7-47c8-acda-5209be358fcf)
    port 84c78095-744c-4415-805f-5f739af3d4d3
        addresses: ["00:1a:4a:17:01:53 dynamic"]
switch 9e77163a-c4e4-4abf-a554-0388e6b5e4ce (ovirt-ovn172-4ac7ba24-aad5-432d-b1d2-672eaeea7d63)
[root@ovmgr1 ~]#

So at the end it could be a missing dependency during install of new packages?

I have to dig a bit more, because from first tests if I start another VM on the same ovn192 network also on the same host they are not able to communicate

Possibly an iptables misconfiguration on host?

I have vnet1 and vnet2 on host now

[root@ov300 ~]# ovs-vsctl show
f1a41e9c-16fb-4aa2-a386-2f366ade4d3c
    Bridge br-int
        fail_mode: secure
        Port br-int
            Interface br-int
                type: internal
        Port "vnet2"
            Interface "vnet2"
        Port "ovn-b8872a-0"
            Interface "ovn-b8872a-0"
                type: geneve
                options: {csum="true", key=flow, remote_ip="10.4.192.34"}
        Port "ovn-1dce5b-0"
            Interface "ovn-1dce5b-0"
                type: geneve
                options: {csum="true", key=flow, remote_ip="10.4.192.32"}
        Port "vnet1"
            Interface "vnet1"
    ovs_version: "2.10.1"
[root@ov300 ~]#

Thanks for the moment

Gianluca