Fun with DNS RCODE’s

NOERROR is the most common DNS return code (RCODE), but there are many other and some of them are very seldom seen in the wild.

NOERROR
FORMERR
SERVFAIL
NXDOMAIN
NOTIMP
REFUSED
YXDOMAIN
YXRRSET
NXRRSET
NOTAUTH
NOTZONE

See the exhaustive list here: https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6

This special DNS record will give you a response with the RCODE you want. Just do a DNS query of <RCODE>._.noerror.org against r1.r41.co and you will get to see some of the rare RCODE’s

Example:

$ dig +noall +comments @r1.r41.co YXDOMAIN._.noerror.org
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: YXDOMAIN, id: 34370
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

Check Your DNS Resolver’s Unicast IP

• https://resolver.r41.co (you can/should refresh a few times)

DNS Lookup Tools Online

• https://mxtoolbox.com/DNSLookup.aspx
• https://dnschecker.org/all-dns-records-of-domain.php
• https://tools.keycdn.com/dig
• https://www.digitalocean.com/community/tools/dns
• https://www.whatsmydns.net/dns-lookup
• https://www.nslookup.io/
• https://hackertarget.com/dns-lookup/
• https://toolbox.googleapps.com/apps/dig/
• https://dnsdumpster.com/
• https://dnslookup.online/
• https://www.cloudns.net/tools/

DNS Propagation Delay Checks Online

• https://dnschecker.org/
• https://www.whatsmydns.net/
• https://dnspropagation.net
• https://dnsmap.io/
• https://www.gdnspc.com/
• https://whatsmydns.me/
• https://www.site24x7.com/tools/dns-propagation.html
• https://kiemtradns.com
• https://showmydns.net/

DNS whoami Records

Google

dig -t TXT +short o-o.myaddr.l.google.com

Akamai

dig +short A whoami.akamai.net 
dig +short TXT whoami.ds.akahelp.net 

DNSSEC Checkers

• https://dnsviz.net/
• https://dnssec-analyzer.verisignlabs.com/
• or: dig +trace +dnssec <domain>

Misc URLs

• Public DNS Servers: https://public-dns.info/