I am at a bit of a loss. I am able to perform an nslookup and a dig on the address "imap.comcast.net" but if I try to ping it or connect to it from my application I get a "Temporary failure in name resolution". Something must be amiss in my DNS configuration but I am unsure what it is.
> ping imap.comcast.net ping: imap.comcast.net: Temporary failure in name resolution > systemd-resolve --status --no-pager Global DNSSEC NTA: 10.in-addr.arpa 16.172.in-addr.arpa 168.192.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa corp d.f.ip6.arpa home internal intranet lan local private test Link 2 (ens3) Current Scopes: DNS LLMNR setting: yes MulticastDNS setting: no DNSSEC setting: no DNSSEC supported: no DNS Servers: 10.0.0.2 DNS Domain: ec2.internal > cat /etc/resolv.conf # This file is managed by man:systemd-resolved(8). Do not edit. # # This is a dynamic resolv.conf file for connecting local clients to the # internal DNS stub resolver of systemd-resolved. This file lists all # configured search domains. # # Run "systemd-resolve --status" to see details about the uplink DNS servers # currently in use. # # Third party programs must not access this file directly, but only through the # symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way, # replace this symlink by a static file or a different symlink. # # See man:systemd-resolved.service(8) for details about the supported modes of # operation for /etc/resolv.conf. nameserver 127.0.0.53 search ec2.internal
Some more forensic information /etc/resolv.conf is a symlink as seen here
> readlink -f /etc/resolv.conf /run/systemd/resolve/stub-resolv.conf
If I change the symlink and restart systemd.resolve I can ping the address but it appears to disable dns caching
>sudo service systemd-resolved stop >sudo rm -f /etc/resolv.conf >sudo ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf >sudo service systemd-resolved start >ping imap.comcast.net >sudo systemd-resolve --statistics DNSSEC supported by current servers: no Transactions Current Transactions: 0 Total Transactions: 0 Cache Current Cache Size: 0 Cache Hits: 0 Cache Misses: 0 DNSSEC Verdicts Secure: 0 Insecure: 0 Bogus: 0 Indeterminate: 0