[dns-operations] cmdns.dev.dns-oarc.net down?

[Viktor Dukhovni]

On Mon, Sep 04, 2023 at 02:28:23PM -0400, Lee wrote:

> dig txt +short  o-o.myaddr.l.google.com
>   gives me the ipv6 address of the resolver

When the resolver happens to use IPv6.  The output is not by itself
IPv6-specific.

> dig txt +short  o-o.myaddr.l.google.com @ns{1,2,3,4}.google.com
>   gives me the ipv4 address

This query is not like the others, it directs the request to Google's
authoritative servers, so you learn your Internet-facing IP address for
reaching those servers, but this need not be how your DNS queries
normally reach those servers.

        ; <<>> DiG 9.18.14 <<>> -t txt o-o.myaddr.l.google.com @ns1.google.com
        ;; global options: +cmd
        ;; Got answer:
        ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42730
        ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
--->    ;; WARNING: recursion requested but not available

        ;; QUESTION SECTION:
        ;o-o.myaddr.l.google.com.       IN      TXT

        ;; ANSWER SECTION:
        o-o.myaddr.l.google.com. 60     IN      TXT     "192.0.2.1"

Which address family is used depends on local address preference
configuration.  On my FreeBSD server, IPv4 is preferred, because IPv6 is
only available via a GRE tunnel to Hurricane Electric.

    $ cat /etc/ip6addrctl.conf
    # Prefer IPv4
    ::ffff:0.0.0.0/96                100     4

    # Prefer IPv6 loopback
    ::1/128                           50     0

    ...

On another system with good IPv6 connectivity, that's what's used by
default in preference to IPv4.

-- 
    Viktor.