Comment 1 for bug 1536754

It looks like this is because we are joining the MACs to the Subnet via the IP address table. If (for whatever reason) the MACs in question don't have IP addresses, it looks like you might hit this issue.

Can you execute "sudo maas-region-admin dbshell" on the region, and then run this query:

https://paste.ubuntu.com/14591836/

I'll paste the query here as well:

SELECT
    subnet.name,
    vlan.vid,
    fabric.name,
    iface.mac_address
FROM
    maasserver_subnet subnet
    LEFT OUTER JOIN maasserver_vlan vlan
        on subnet.vlan_id = vlan.id
    LEFT OUTER JOIN maasserver_fabric fabric
        on vlan.fabric_id = fabric.id
    LEFT OUTER JOIN maasserver_interface iface
        on iface.vlan_id = vlan.id
ORDER BY subnet.name, vlan.vid, iface.mac_address;