Where is nameserver address coming from?

Moving this question to this forum

Is it required for the MAAS server to have an interface on all the subnets defined in MAAS? Initially i only had 2 interfaces on MAAS host; 1 internal 1 external. But then I added interfaces connected to the VLANs i created in MAAS for OpenStack. Is that overkill for the MAAS host?