Re: em0: No buffer space available for IPv6 traffic but IPv4 is OK

On 19.08.2023 00:54, Kevin Oberman wrote:
>     Interestingly, there is incoming IPv6 local broadcast traffic as
>     sniffed
>     by
>     # tcpdump -n -i em0 ip6
>     (ICMP6, neighbor solicitation, UDP from LAN link local addresses).
> 
>     Has anyone seen this before and can suggest a fix?
> 
>     Reboot did not solve, no software updates made, no config changes, just
>     stop working from one day to the next.
> 
> Oddly, ENOBUFS is the error I get when my firewall is blocking transmit 
> traffic. There may well be other causes.

Yes, network stack returns this error usually when it is unable to send 
data. And this could be due to many different causes.

First of check that prefixes and masks are correctly configured. Then 
check that your IPv6 default gateway is directly reachable and its layer 
2 address is known. Also you can check `netstat -s` to find what counter 
grows when you try to use IPv6. Make sure your firewall doesn't block 
ICMPv6 types needed for IPv6 to work. Check that multicast functions 
correctly.

   # ifconfig
   # ndp -an
   # netstat -s
   # ifmstat

-- 
WBR, Andrey V. Elsukov