On Wed, Nov 8, 2023 at 1:56 PM Michael S. Keller via Dng
<dng@???> wrote:
>
> My oldest Linux host has trouble with IPv6. Apparently it's the only
> host in my home network that does have trouble with it (of those that
> can do IPv6), and I've run out of ideas. All tests are in the same
> network - traffic does not cross into my ISP's area. The same symptom
> has persisted across two different switch/router combos - first an old
> Airport Extreme, now a TP-Link Deco XE75.
>
> Seeking new perspective on this symptom.
>
> What happens: IPv6 TCP sockets start out fast, then after a few seconds,
> they stall for a bit, then recover, then stall again, and this repeats.
> This never happens with IPv4, so I usually disable IPv6 for the onboard
> network interface with
>
> net.ipv6.conf.eth0.disable_ipv6 = 1
>
> in sysctl.conf.
>
> My other two Linux hosts, one desktop (Intel 4th-gen i7) and one
> VirtualBox VM, don't show this symptom.
>
> So far the kernel version doesn't seem to matter.
>
> The troublesome host has an AMD Phenom II X6 CPU from ~2011, uses the
> r8169 driver for its NIC, and currently runs kernel package
> linux-image-amd64=6.1.55-1. It cannot yet run a later kernel because of
> the old nVidia discrete GPU in it - nvidia-legacy-390xx driver won't
> compile on later kernels from Devuan repositories.
>
I'm in the process of moving to OPNsense for firewall and router.
OPNsense runs on a hardened FreeBSD (iirc).
Their recommendation is to ditch the Realtek populated systems
and use systems with Intel networking chips. (The Realtek chips are
cheaper which I'd bet is why they're so common/popular.)
Dunno if that's your actual issue but the community is quite adamant
about - - - 'don't touch Realtek' .

HTH