Reliably detecting the absence of IPv6

[Philip Prindeville]

> On Dec 11, 2025, at 9:19 AM, David Härdeman <david at hardeman.nu> wrote:
> 
> December 11, 2025 at 8:41 AM, "Jonas Lochmann" <openwrt at jonaslochmann.de> wrote:
>> Am Wed, Dec 10, 2025 at 08:44:00PM -0700, schrieb Philip Prindeville via openwrt-devel:
>> 
>>> 
>>> We had an issue where residential customers on US ISP’s with IPv4 (even if it’s NAT’d) would see a lot of logging from named about not being able to reach IPv6 name servers to resolve AAA records.
>>> 
>> 
>> Are you talking about A or AAAA records?
> 
> I'm guessing it's rather about being unable to reach nameservers via IPv6...and not any specific kind of record.


Yes, correct.


> 
>>> 
>>> The workaround is to run bind with ‘-4’ to eliminate this.
>>> 
> 
> Why not remove the log messages instead?
> 
> Haven't tested it (and haven't seen the exact log messages you're seeing), but something like this:
> 
> logging {
>   category lame-servers { null; };
> };


Because that might interfere with troubleshooting when legitimate name servers aren’t reachable for pathological reasons.