When you set the metric to 15 in Router→OSPF→Areas→0.0.0.0→Interface→[interface id]→Metric, the routing table of the firewall will set the OSPF route to all OSPF peer IP addresses as that metric.

When a fireawll sets Router→OSPF>Export Rules and then selects a redistribution profile to ensure routes are exported, whatever is set in the Export Rule→Metric is going to be the route set on the other firewalls if New Path Type = Ext2. If New Path Type = EXT 1, then the other firewalls will set the metric of the routes learned from this firewall to the value in Router→OSPF→Export Rule→Metric added to the value on the other firewall's Router→OSPF→Areas→0.0.0.0→Interface→[interface id]→Metric.

If you enable OSPF and export a redistribution profile that has the source type configured but no filters, all routes will be exported.

When setting OSPF over VPN links (tunnel interfaces), make sure the Router→OSPF→Areas→0.0.0.0→Interface→tunnel.9→Link Type is set to p2p.

When you have a firewall with a leg in 0.0.0.0 and a leg in 0.0.0.2, if you configure “Range” in 0.0.0.0 with the summary path you want, that summary will be distributed, along with all other routes, into 0.0.0.2.

If you have two firewalls (active/active) doing this, then set the area 0.0.0.0→Interface metric of the primary to 10 and the area 0.0.0.0→Interface metric of the secondary to 11 and that means OSPF peers in 0.0.0.2 area will prefer to get their 0.0.0.0 area routes from the primary

If you want to redistribute loopback addresses, you will need to create a local static route that points the loopback IP (/32) to itself (IP) as the next hop. You can then redistribute the static route.

To see routes being learned by OSPF, use the following command

show routing protocol ospf lsdb