options/glue-checking: normal|strict|permissive

Default:

normal

The resolver strictness checking level.

By default, resolver runs in normal mode. There are possibly many small adjustments hidden behind the mode settings, but the main idea is that in permissive mode, the resolver tries to resolve a name with as few lookups as possible, while in strict mode it spends much more effort resolving and checking referral path. However, if majority of the traffic is covered by DNSSEC, some of the strict checking actions are counter-productive.

Glue type	Modes when it is accepted	Example glue [1]
mandatory glue	strict, normal, permissive	ns1.example.org
in-bailiwick glue	normal, permissive	ns1.example2.org
any glue records	permissive	ns1.example3.net

[1]

The examples show glue records acceptable from servers authoritative for org zone when delegating to example.org zone. Unacceptable or missing glue records trigger resolution of names listed in NS records before following respective delegation.