Re: Anybody Using IPv6?

On 2025-05-20 19:43, Marc Haber wrote:

"Carlos E. R." <robin_listas@es.invalid> wrote:

Consider that, for instance, this laptop has an IPv6 address:
>
cer@Isengard:~> ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
         inet 192.168.1.16  netmask 255.255.0.0  broadcast 192.168.255.255
         inet6 fc00::16  prefixlen 64  scopeid 0x0<global>
         inet6 fe80::4ecc:6aff:fe61:50a1  prefixlen 64  scopeid 0x20<link>
         ether 4c:cc:6a:61:50:a1  txqueuelen 1000  (Ethernet)
...

 This laptop has an IPv6 link local address.

I know. That one is automatic.
And also a given global address that I personally wrote.

 Btw, the GNU/Linux world has been using iproute2 for two decades now.

I am aware.

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:~>

 

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.
--
Cheers,
        Carlos E.R.