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 threadDrazi CrendravenJan 17, 2023

@sindarina

Thanks for the reminder.

I generally use 10.x.x.x, which I know at least can't get out.

A question, though. How can 0.0.0.0/8 reference a single host, and 10.0.0.0/8 reference a whole network?

Are there IP addresses such as 0.0.0.1 that I've never seen?

Show threadPhilipp Meier
@drazisil @sindarina the 10/24 net is likely to be used in many cases so better use the officially unriutable test networks.
Jan 17, 2023 at 6:33amWeb