[lxc-users] IPv6: Neighbour table overflow

[Serge Hallyn]

Quoting Tamas Papp (tompos at martos.bme.hu):
> hi All,
> 
> I spent the whole day with debugging a weird network issue. On our
> network there were packet losses, ping timeout and everything you can image.
> I was sure, there is a loop, or faulty switch, but wasn't able really
> identify the root. Sometime it was better, then the packet losses came
> back after a while (last time after 5 hours...).
> 
> Then I looked into syslog on one of servers and I saw many messages like
> this:
> 
> [772718.275810] IPv6: Neighbour table overflow

http://cosu.ro/blog/2011/09/26/ipv6-neighbour-table-overflow/ makes it
sound like those are just magic values, and suggests raising them
without looking into why (which I'm not saying I agree with :)

http://www.arcweb.ro/blog/2011/12/13/neighbour-table-overflow-debug-ipv4-and-ipv6/
suggests blaming "occasional big spike of IPv6 ARP requests".  Which
could be just an accident...  or could be some sort of attack.

...

> The system was running without any glitch for months.
> Any idea?

I'm ashamed to admit I *still* haven't dived into the ipv6
pool.  The msgs mean nothing to me.  Maybe this rings a bell for
Stéphane?

Anyway if you don't actually use ipv6, then certainly disabling
it seems the safer option.  I prefer to disable code I'm not using.