Just want to confirm/correct my understanding of how CNAME delegation works
if I have a CNAME cdn.example.com in my DNS that points to a third party CNAME cdn.thirdparty.com, can that third party register an A record in their DNS along the lines of test.cdn.thirdparty.com ?
i.e can they register 2nd level subdomains if their name server is now effectively responsible for resolving cdn.thirdparty.com ? or can only register an A record for cdn.thirdparry.com ?
Thanks