In my experience, you can and will encounter a situation with conflicting resolvings of .internal unless the use is all properly scoped to broadcast and adminis

In my experience, you can and will encounter a situation with conflicting resolvings of .internal unless the use is all properly scoped to broadcast and administrative zones (ha ha ha fat chance, though respect to anyone who really tries). .lan, .home, and similar have the issue that they aren't actually reserved so they can conflict (see the land-grab of .dev that Google did after ICANN opened up TLDs). The one way that has most stability (and is best recommendation I have seen) is to have a publicly reserved zone, which doesn't need to have anything other than NS records pointing to hostnames visible from your internal networks (I am always tempted to have essentially NS -> AAAA + PTR pointing at anycast internal v6 address). Turns out it does not need to be separate domain from some other domain of yours, it can be let's say i.your-company-name.com. - I am partial to your-company-name.net. but that can be confusing for less computer crazy people.