On Sun, 9 Nov 2014, Antonio Querubin wrote:

> On Fri, 7 Nov 2014, Antonio Querubin wrote:
>
>> I was wondering if anyone else has noticed whether IPv6 neighbor discovery 
>> is broken after upgrading a IPv6-only kvm host to kernel 2.6.32-504? This 
>> also appears to affect guest to host and guest to guest IPv6 connectivity.
>> 
>> Oddly enough, on a kvm host with IPv4 but not IPv6, the guests CAN 
>> communicate over IPv6.
>
> Update:  downgrading the kernel to 2.6.32-431 on the IPv6-only kvm host
> restored IPv6 ND functionality for both host and guests.

I updated to 2.6.32-504.1.3 and the problem continues.  Ran some more 
tests and found that I can restore ND functionality by either flushing the 
cached ND records or just running tcpdump.  However, after some time, the 
problem reappears.  After some more googling I found this recent bug 
report on the CentOS Bug Tracker describing similar symptoms.

http://bugs.centos.org/view.php?id=7796

However, as far as I can tell there's no known workaround other than 
downgrading the kernel to something prior to 2.6.3-504.

Antonio Querubin
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