Hacker News Reader

Comment by boredatoms | Hacker News Reader

What are the use cases for it beyond the regular .1 address that you dont get from ::1?

It's very useful for cooperatively pretending that a single machine is actually a network of machines, without all the madness of network namespaces.

Basically every server program ever supports the notion of "which IP address am I supposed to bind to?" Normally the answer is either "localhost" or "whatever my LAN or WAN address is, for a particular interface". And specifying this (both for servers and for clients) is much less effort than replacing all the standard-ish ports with ad-hoc ones.

I love this feature so much when jumping back and forth between two projects that when devving expect exclusive control of postgres. All I have to do is set the bind address for one .1 and the other .2 and all is good.

You can literally do the same thing with IPv6.

Just assign multiple IPv6 to your loopback interface and everything will work as expected. You can use either private IPv6 or even link-local IPv6 range.

There’s no need to waste thousands of addresss on this use case.

> waste thousands

Yeah would hate to run out

Which is configuration that's requires arcane invocations and permissions I might not have.

As opposed to IPv4, where everything Just Works™.

…until it doesn't, when something looks at the configured addresses. The "other" addresses in 127.0/8 will easily have weird behavior in nontrivial setups.

I wish that were true. MacOS for example only assigns 127.0.0.1/32. You have to assign extra IPs manually, the same way you would on IPv6.

that is a mac problem, not an ipv4 problem. The mac does a lot of pretty stupid things

As someone who used Windows and Linux my whole career and now am forced to use Mac for a new job; I completely agree, I was right, Mac is a very weird thing overall.

Same thing on FreeBSD. It's just not something you can rely on and the spec doesn't say it needs to be assigned.

Yeah, and I always do.

Because parent is right, having multiple loopback addresses is just so nice for a lot of things.

I was counting on that just a few days ago and failed spectacularly when Windows SMB client refused to connect to 127.0.0.2

Reply on news.ycombinator.com