17 Nov
2020
17 Nov
'20
5:48 p.m.
Hi,
I’m trying and failing to get overlay network traffic working between Docker containers on
different VPS hosts. The issue seems to be that neither host is sending VXLAN data on
port 4789. I’ve been getting help on Docker’s IRC channel and the suggestion there is
that issues have been seen before with this and interaction with other virtualisation
technologies (VMware, for example) which also use VXLAN. Does anyone know if there are
issues using swarm/overlay networking between Xen VPS hosts?
Regards,
Chris
—
Chris Smith <space.dandy(a)icloud.com>
17 Nov
17 Nov
6:06 p.m.
Hello,
On Tue, Nov 17, 2020 at 05:48:53PM +0000, Chris Smith via users wrote:
I’m trying and failing to get overlay network traffic
working
between Docker containers on different VPS hosts. The issue seems
to be that neither host is sending VXLAN data on port 4789.
[…]
Does anyone know if there are issues using
swarm/overlay
networking between Xen VPS hosts?
I can't see any reason why there would be a problem, but I don't
know anything about vxlan.
Are you saying that when you tcpdump on one host looking for port
4789 traffic (TCP? UDP?), you do not see anything when you think you
should?
You should be able to send any unicast traffic you like, though you
cannot do broadcast / multicast since each VM is in its own
broadcast domain with just itself and the host its on.
Cheers,
Andy
--
https://bitfolk.com/ -- No-nonsense VPS hosting
7:26 p.m.
Hi Andy,
On 17 Nov 2020, at 18:06, Andy Smith
<andy(a)bitfolk.com> wrote:
Are you saying that when you tcpdump on one host looking for port
4789 traffic (TCP? UDP?), you do not see anything when you think you
should?
Yes, exactly. I’m following the guide here:
https://docs.docker.com/network/network-tutorial-overlay/
<https://docs.docker.com/network/network-tutorial-overlay/> for standalone
containers on different hosts. Everything is working fine until I try to ping one
container from the other — or indeed try any form of network connectivity. Traffic is
going back and forth correctly on ports 2377 and 7946 but tcpdump shows that neither host
is initiating traffic on port 4789 (UDP). Firewalls are disabled on both hosts, so that’s
not an issue. Networking is fundamentally working on both containers — that is they can
see the internet and other containers.
Regards,
Chris
—
Chris Smith <space.dandy(a)icloud.com>
18 Nov
18 Nov
5:35 a.m.
Hello,
On Tue, Nov 17, 2020 at 07:26:14PM +0000, Chris Smith wrote:
Traffic is going back and forth correctly on ports
2377 and 7946
but tcpdump shows that neither host is initiating traffic on port
4789 (UDP).
I am not seeing a problem sending data on udp/4789 between VMs on
different hosts:
Window 1:
$ sudo iptables -P INPUT ACCEPT
$ sudo iptables -F
$ sudo iptables -X
$ nc -v -l -u -p 4789
listening on [any] 4789 ...
Window 2:
$ nc -u 85.119.80.223 4789
hello world
^C
Window 1:
connect to [85.119.80.223] from authns0.bitfolk.com [85.119.80.198] 54925
hello world
That sent data between a VM on leffe and a VM on limoncello, which
are actually in two different rooms in Telehouse.
I might see if I can follow the docker example you linked to, though
I have no experience whatsoever of docker…
Cheers,
Andy
--
https://bitfolk.com/ -- No-nonsense VPS hosting
9:15 a.m.
Hi Andy,
On 18 Nov 2020, at 05:35, Andy Smith
<andy(a)bitfolk.com> wrote:
I am not seeing a problem sending data on udp/4789 between VMs on
different hosts:
[…]
connect to [85.119.80.223] from authns0.bitfolk.com
[85.119.80.198] 54925
hello world
Thanks, I think I’ve narrowed this down now. For some reason Docker is having trouble
sending port 4789 (and only that port) traffic using IPv6. When I force Docker to use
IPv4 then it works as expected. I repeated your test using nc with IPv6 and there is no
host-to-host issue here. Very strange, but it seems that it’s nothing at all to do with
the VPS.
Regards,
Chris
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