1. .arpa is just another DNS zone – you can store any record type
“It's just a domain. You can put anything into your zone. A, AAAA, PTR, TXT, you can even put HESIOD records if you want to party like its Kerberos nineteen ninety IV.” – ggm
2. The term “DNS propagation” is debated – some say it’s a myth, others see it as a descriptive process
“A lie. DNS doesn't propagate.” – megagpt1
“I don't see what's wrong with calling that process propagating a change… By changing the results on the authoritative and as caching recursive resolvers requery, the new results spread out and affect a greater number.” – toast0
“whoops good catch, I had thought it was a synonym for the record TTL's expiring.” – ethanhawksley
3. Practical obstacles when using .arpa (TLS certs, prefix stability, abuse)
“Most certificate authorities will not issue certs against .arpa domains… I spent months trying to get a refund… only caved once I threatened a chargeback.” – RKearney
“If you don't use it at all, they do take the prefixes away… I lost a prefix when I did a house move…” – toast0
“Unfortunately the he.net tunnels are used for a lot of abuse now and you [are] treated like a bot if you use them to go to popular websites.” – toast0