[Users] OpenVZ on EL6 - weird network issue

Scott Dowdle dowdle at montanalinux.org
Sat Dec 27 12:40:15 PST 2014


----- Original Message -----
> Symptoms:
> =========
> All nodes and VPS's sporadically get unreachable from the outside. From
> within the private network (from another box for example) one can still
> SSH in. Pings to public IPs then still work from the nodes, but no
> longer work from inside the VPS's.

I have seen this reported in the #openvz IRC channel a number of times over the years and almost always it was inside of a commercial datacenter.  The cause of the problem seemed to be some upstream routing device that was periodically dropping ARP table entries for the containers.  I'm not much of a networking person so forgive me for a lack of precision of language.  Anyway, one workaround to fix it was to periodically (via cron or whatever) do an arpsend from the host (or maybe each container?) to keep the ARP entries refreshed.  I don't remember the specifics of the arpsend method but in a pinch you can probably look at how vzctl (in the C source code) sets up a container's IP address... and mimic that.

I'd like to hear more once you get it figured out.

Scott Dowdle
704 Church Street
Belgrade, MT 59714
(406)388-0827 [home]
(406)994-3931 [work]

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