[v6ops] Re: 464XLAT-only networks

[Marco Moock <[e-mail]>]

On 25.10.2024 10:27 Lorenzo Colitti wrote:

> The problem with such a network is that the host doesn't know that
> the IPv6 internet is reachable. Because IPv6 stacks generally prefer
> IPv6 over IPv6, that typically results in high latency and failures.

If the machine has a default route (or route to the unreachable
destination) and a global-scoped address (can be ULA too), it will
prefer IPv6.
If the connectivity is broken, this is the place where stuff needs to
be fixed and not using crappy workarounds.

> Here are the first three problems I can think of:
> 
>    - Client code that cannot fall back from IPv6 to IPv4 won't work
>    - getaddrinfo will always issue AAAA lookups as well as A lookups,
>    slowing down DNS lookups
>    - HE implementations that bias towards IPv6 (which I think is
> suggested or required by the RFC) will encounter latency penalties.
> 
> There are probably more.

If IPv4 doesn't work, this problem exists too and network operators are
then going to fix that.
Why don't apply that to IPv6?