If the ovn-northd instance is not running on the same node as OVN NB and OVN SB database, then you will need to follow the steps below to secure the communication between ovn-northd and NB/SB databases.
On the node running ovn-northd daemon, run the following commands.
cd /etc/openvswitch
ovs-pki req ovnnorthd
The above command will generate a private key "ovnnorthd-privkey.pem" and a corresponding certificate request named "ovnnorthd-req.pem". Copy over the ovnnorthd-req.pem to the secure machine's (where you have installed the ovs-pki utility) /var/lib/openvswitch/pki folder to sign it using the command below.
ovs-pki -b sign ovnnorthd
The above command will generate ovnnorthd-cert.pem. Copy over this file back to the ovn-northd node's /etc/openvswitch foler. The ovnnorthd-privkey.pem and ovnnorthd-cert.pem will be used by the ovn-northd to communicate with OVN NB and SB database.
Now run the following command to ask ovn-northd to use these certificates.
cat > /etc/openvswitch/ovn-northd-db-params.conf << EOF
--ovnnb-db=ssl:$CENTRAL_IP:6641 --ovnsb-db=ssl:$CENTRAL_IP:6642 \
-p /etc/openvswitch/ovnnorthd-privkey.pem -c /etc/openvswitch/ovnnorthd-cert.pem \
-C /etc/openvswitch/cacert.pem
EOF
/usr/share/openvswitch/scripts/ovn-ctl restart_northd