Owen DeLong wrote:

On Nov 20, 2021, at 19:11 , Joe Maimon <jmai...@jmaimon.com> wrote:



Owen DeLong wrote:
I guess I don’t see the need/benefit for a dedicated loopback prefix in excess 
of one address. I’m not necessary inherently opposed to designating one (which 
would be all that is required for IPv6 to have one, no software updates would 
be necessary), but I’d need some additional convincing of its utility to 
support such a notion.
Since the loopback prefix in IPv4 is present and usable on all systems, IPv6 
parity would require the same, so merely designating a prefix would only be the 
beginning.

There may not be a need. But there is clearly some benefit.
Which is? You still haven’t answered that question.

You have right below.

And if there is indeed no benefit, than there is no reason not to repurpose 127/8 considering that you may use many other ranges in IPv4 for loopback and that you can just use IPv6 for loopback and there you go you have a whole /10.

Its not like it will overnight cause system admin headaches. And they should be running their loopback apps on IPv6 anyways.

Well, technically, fe80::/10 is also present and predictable on every loopback 
interface. It does come with the additional baggage of having to specify a 
scope id when referencing it, but that’s pretty minor.


Nope… It’s every bit as deterministic as 127.0.0.0/8.

If you send packets to fe80::*%lo0 on a linux box, they’ll get there. If you 
try it on something other than linux, it probably doesn’t work.
That’s also true of 127.*.*.*.

So fe80::/10 is the loopback prefix for IPv6


Joe

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