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Comment by lxgr | Hacker News Reader

Are URLs of link local addresses a common thing with IPv6? I don’t think I’ve ever encountered one myself (but my home network supports ULAs and more importantly DNS).

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Link local addresses are exactly that. They don't route and they are for low level stuff like adding stuff to the routing table or BGP.

If you want to do this properly then you configure a Unique Local Addresses (ULA) out of the range fc00::/7. These are the equivalent of 192.168 or 172.16 or 10. and they can be routed.

Trying to run services on fe80: addresses is a mistake IMHO

So then shouldn't the link-local address be either MAC-derived or random, especially if you have multiple ifaces? The article's fe80::4 example seems weird. Mine is fe80::18cf:85a3:bc97:d117.

It usually is, but I don't think it has to be. You can definitely manually assign link-local addresses.

Note that even a MAC-derived link-local may not be unique, since the same MAC can be on both networks (e.g. with VLANs, or if you assign MACs to hosts instead of NICs).

No. A well set up network never needs them at all. But I can see the usefulness

Think of that you want to Provision a "smart device" with just a computer and no router.

These link local addresses are quiet handy. But sadly the parsing of these with modern browsers is a flame war ever since. I assume that's the reason why we don't see its usage that often.

Another nice use case is to use these link local addresses in cloud environments...

mDNS should work here even without a reflector.

Nobody is talking about mdns here. I don't know where you got this from.

mDNS allows you to access a local HTTP service via IPv6 without IP-based URLs, so it seems pretty relevant.

Not common, but should be permissible if you want any kind of consistency in your software.

They'd be more common if browsers didn't completely break handling them.

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