Sindarina, Edge Case DetectiveJan 16, 2023

Since I just saw yet another developer use '1.2.3.4' in an example configuration, a reminder that you MUST NOT use publicly routable addresses that you do not control in your code.

Instead, use one of the available 'TEST-NET' IPv4 or IPv6 ranges documented in RFC 6890, such as;

192.0.2.0/24
198.51.100.0/24
203.0.113.0/24

❌ 1.2.3.4
✅ 192.0.2.4

Pass it on to all of your fellow developers, documentation writers, and so forth.

Full RFC is here;

https://datatracker.ietf.org/doc/rfc6890/

RFC 6890: Special-Purpose IP Address Registries

This memo reiterates the assignment of an IPv4 address block (192.0.0.0/24) to IANA. It also instructs IANA to restructure its IPv4 and IPv6 Special-Purpose Address Registries. Upon restructuring, the aforementioned registries will record all special-purpose address blocks, maintaining a common set of information regarding each address block.

IETF Datatracker
Show threadJulian Andres Klode 🏳️‍🌈
@sindarina And I'm the evil person actually assigning these addresses in DNS66 for DNS "VPN" because I had no idea how to pick addresses that don't conflict with real world IPs. I guess now I could have scanned the network list and found a free IP range
Jan 16, 2023 at 8:32pmMastodon for Android
Show threadSindarina, Edge Case DetectiveJan 16, 2023
@juliank There's always the '100.64.0.0/10' shared address space, if you want to avoid conflict with RFC 1918 private IPv4 and such. Tailscale uses that, for example.
Show threadyetztJan 16, 2023
@juliank in some freifunk mesh networks 6/8 was used internally, because thats us army and noone wants to connect there.