FreeBSD does not reply to IPv6 Neighbor Solicitations

[Bjoern A. Zeeb]

On 4 Jan 2021, at 14:17, Lutz Donnerhacke wrote:

>> Victor Sudakov wrote:
>>> Dear Colleagues,
>>>
>>> Why could it be that a FreeBSD 12.2 host does not reply to ICMPv6
>>> Neighbor Solicitations from the router?
>>
>> Any ideas please?
>
> Thank you for pointing this out.
> I do have an similar effect, after upgrading, and you point me to a 
> good
> direction.
> I'll investigate and report back.


I’d start by checking netstat -s -p icmp6 and netstat -s -p ip6  for 
any suspicious counter updates.

Another thing to do might be to turn on nd6 log/debugging by sysctl  
(sysctl net.inet6.icmp6.nd6_debug=0xff should do it) and keep an eye on 
the kernel messages.


/bz