On 11/14/23 18:50, Gregory Nowak via Dng wrote:
> # sysctl net.ipv6.conf.all.router_solicitation_max_interval
> net.ipv6.conf.all.router_solicitation_max_interval = 3600
>
> If this is the same on the host in question, then that likely isn't
> the problem.

It is.

$ sysctl net.ipv6.conf.all.router_solicitation_max_interval
net.ipv6.conf.all.router_solicitation_max_interval = 3600

>
>
> Are the periods between stalls, and the time during stalls random, or
> the same lengths most of the time?

Today, I couldn't get it to go fast in one direction (from my desktop to
this machine).

From this machine to my desktop was fast for a few seconds, then
stalled, 16 seconds into the dd | nc operation, and stayed stalled.

As before, IPv4 works fine in both directions, with no stalls.

>
> How are interfaces on this host configured, in
> interfaces/interfaces.d, network manager, some other way?

/etc/network/interfaces:

auto eth0
iface eth0 inet6 dhcp
iface eth0 inet static
         address 192.168.1.12
         network 192.168.1.0
         netmask 255.255.255.0
         broadcast 192.168.1.255
         gateway 192.168.1.1

For the desktop-to-server direction, Wireshark shows TCP Dup ACKs,
Spurious Retransmissions, TCP Resets. I can send the output, if it helps.

If I run ndisc6 from the server, against the desktop's IPv6 address,
only one MAC is returned, so I hopefully there's not a duplicate address.

-Michael