subdomain secondary, into the parent z.com zone file and then sending that out to z.com's secondary name servers. It all works, but, I can't figure out why it works. What is telling the primary for z.com to merge the z.com subdomains when z.com has not offically delegated them? There is no reference to the subdomains in the zone file for z.com. At all. Regards, Alan Kirchhoff