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From: "Carlos E. R." <robin_listas@es.invalid>
Newsgroups: comp.os.linux.misc
Subject: Re: Anybody Using IPv6?
Date: Wed, 21 May 2025 03:46:45 +0200
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On 2025-05-20 23:14, Marc Haber wrote:
> "Carlos E. R." <robin_listas@es.invalid> wrote:
>> On 2025-05-20 19:43, Marc Haber wrote:
>>> What does the IPv6 routing table of the system in question say?
>>
>> I don't have a problem with the laptop currently. The problem was some
>> years ago, on several computers.
>>
>> cer@Isengard:~> ip route
>> default via 192.168.1.1 dev eth0
>> 192.168.0.0/16 dev eth0 proto kernel scope link src 192.168.1.16
>> cer@Isengard:~>
> 
> That is not the IPv6 routing table.

That is all there is.

> 
>>>> So applications thought that IPv6 was available.
>>>
>>> Tries to use it, gets a host unreachable, SHOULD¹ try again with the
>>> next IP address associated with the target hostname, which might
>>> happen to be IPv4, tries to use it, connects successfully.
>>>
>>> Different behavior is a bug.
>>>
>>> ¹ in the RFC2119 sense
>>
>> The gai change makes things go faster, by not trying IPv6 first.
> 
> On a slow machine, about a millisecond, yes. That matters in high
> performance computing, where professionals do the administration. It
> does absolutely not matter on a personal workstation that spends 99 %
> of its CPU cycles waiting for keystrokes anyway.

It is the network speed that matters, which is much slower.

-- 
Cheers,
        Carlos E.R.