On Thu, 10 Dec 2015 16:00, m.roth@... wrote:

We've started having a problem with a CentOS 7 server. It looses its IPv6
address, if I understand this issue correctly. We can get in, if we do ssh
-4, though.

In the logs, I'm seeing this about twice an hour:
<warn>  (pid 98466) unhandled DHCP event for interface ens3f0

Now, in googling, I get very few hits putting quotes around "unhanded dhcp
exception" - in fact, the only one I found that seemed to talk about it
was from someone's slackware box, where there was some sort of
configuration, perhaps similar to ifcfg-<if>, and they were telling that
person to remove it, because it conflicted with what Networkmanager was
trying to do, leaving it in a confused state.

Any thoughts?

      mark

My first thought upon reading this was:
Well, let's block / drop the irritating packets via firewall / iptables.

Is the source of these packets allowed to contact your box at all?
 - No : then block it fully, ipv4 and ipv6
 - Yes: block all dhcpv4 / dhcpv6 / radv traffic to and from this source.
   or even more aggressive: first block this box, second only open the
   minimum required ports to that box.

IMHO, Networkmanager(and its underlaying helpers) should be much more
carefull in handling Router / DHCP stuff.
It's biggest niggle for me is a missing white- and black-list for
(dis-)allowed routers / dhcp-servers.

Is this the "Right(tm)" thing to do? Dunno, but that would be my gut-telling.

 - Yamaban

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