Tell HN: 1.1.1.1 appears to be down

DNS shouldn't be tested with ICMP. Try dig or nslookup instead. ICMP echo request/reply may help to decide reachability and nothing more.

This is a reasonable test of the DNS service on 1.1.1.1:

  $ dig @1.1.1.1 www.cloudflare.com A

  ; <<>> DiG 9.20.4-3ubuntu1.1-Ubuntu <<>> @1.1.1.1 www.cloudflare.com A
  ; (1 server found)
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34112
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags:; udp: 1232
  ;; QUESTION SECTION:
  ;www.cloudflare.com.            IN      A

  ;; ANSWER SECTION:
  www.cloudflare.com.     36      IN      A       104.16.123.96
  www.cloudflare.com.     36      IN      A       104.16.124.96

  ;; Query time: 39 msec
  ;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
  ;; WHEN: Mon Jul 14 23:32:57 BST 2025
  ;; MSG SIZE  rcvd: 79

[EDIT]:

  $ ping 1.1.1.1
  PING 1.1.1.1 (1.1.1.1) 56(84) bytes of data.
  From 141.101.70.116 icmp_seq=1 Time to live exceeded
  64 bytes from 1.1.1.1: icmp_seq=2 ttl=50 time=126 ms

So ping fails a bit (and then works - firewall) but DNS works.

The service required is DNS not ping. Test the service.