1. DNS/用語/superglue

sibling domain内の名前を指すNSに対してのAレコードをsibling domain glueと呼ぶ人がいる。

https://fanf.livejournal.com/145708.html Domain registry APIs and "superglue" - Tony Finch's blog

Sticky problems

There is also a problem with glue records:

my idea was that superglue would only need address records for nameservers that are within the domain whose delegation is being updated.

This is the minimal set of glue records that the DNS requires, and in many cases it is easy to pull them out of the master file for the delegated zone.

1.1. sibling domain

However, sometimes a delegation includes name servers in a sibling domain. For example, cam.ac.uk and ic.ac.uk are siblings. 

    cam.ac.uk.  NS  authdns0.csx.cam.ac.uk.
    cam.ac.uk.  NS  ns2.ic.ac.uk.
    cam.ac.uk.  NS  sns-pb.isc.org.
    ; plus a few more

In our delegation, glue is required for nameservers in cam.ac.uk, like authdns0; glue is forbidden for nameservers outside ac.uk, like sns-pb.isc.org. Those two rules are fixed by the DNS.

But for nameservers in a sibling domain, like ns2.ic.ac.uk, the DNS says glue may be present or omitted.

1.2. registries

In registries which require optional sibling glue, there is a quagmire of problems. In many cases the glue is already present, because it is part of the sibling delegation and, therefore, required - this is the case for ns2.ic.ac.uk. But when the glue is truly optional it becomes unclear who is responsible for maintaining it: the parent domain of the nameserver, or the domain that needs it for their delegation?

I basically decided to ignore that problem.

I think you can work around it by doing a one-off manual set up of the optional glue, after which superglue will work. So it's similar to the other delegation management tasks that are out of scope for superglue, like registering or renewing domains.

1.3. sibling glue

named-checkzoneの説明に現れる

https://ftp.isc.org/isc/bind9/cur/9.12/doc/arm/man.named-checkzone.html