How to troubleshoot DNS failure and updated changed IP in Route 53 (AWS)


After reboot of EC2 instance, public IP changed – while nslookup and dns was pointing to old IP, hence the website stopped working.

[root@ctrwebtest html]# nslookup ctrwebtest
Server: 192.168.0.2
Address: 192.168.0.2#53

Non-authoritative answer:
Name: ctrwebtest.ctrworld.com
Address: 34.218.60.21 ————– Old IP

[root@ctrwebtest html]#

Use the dig command to perform a lookup against the client DNS server that’s configured in the host’s /etc/resolv.conf file.


[root@ctrwebtest html]# dig ctrwebtest.ctrworld.com

; <<>> DiG 9.9.4-RedHat-9.9.4-74.amzn2.1.2 <<>> ctrwebtest.ctrworld.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4725
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;ctrwebtest.ctrworld.com. IN A

;; ANSWER SECTION:
ctrwebtest.ctrworld.com. 169 IN A 34.218.60.21 —– Old IP

;; Query time: 0 msec
;; SERVER: 192.168.0.2#53(192.168.0.2)
;; WHEN: Wed Aug 31 18:46:47 UTC 2022
;; MSG SIZE rcvd: 68

If you add the +trace variable, the dig command can also perform a recursive lookup of a DNS record, as shown in the following example:

[root@ctrwebtest html]# dig +trace ctrwebtest.ctrworld.com

; <<>> DiG 9.9.4-RedHat-9.9.4-74.amzn2.1.2 <<>> +trace ctrwebtest.ctrworld.com
;; global options: +cmd
. 518400 IN NS G.ROOT-SERVERS.NET.
. 518400 IN NS H.ROOT-SERVERS.NET.
. 518400 IN NS I.ROOT-SERVERS.NET.
. 518400 IN NS J.ROOT-SERVERS.NET.
. 518400 IN NS K.ROOT-SERVERS.NET.
. 518400 IN NS L.ROOT-SERVERS.NET.
. 518400 IN NS M.ROOT-SERVERS.NET.
. 518400 IN NS A.ROOT-SERVERS.NET.
. 518400 IN NS B.ROOT-SERVERS.NET.
. 518400 IN NS C.ROOT-SERVERS.NET.
. 518400 IN NS D.ROOT-SERVERS.NET.
. 518400 IN NS E.ROOT-SERVERS.NET.
. 518400 IN NS F.ROOT-SERVERS.NET.
;; Received 239 bytes from 192.168.0.2#53(192.168.0.2) in 26 ms

com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 86400 IN DS 30909 8 2 E2D3C916F6DEEAC73294E8268FB5885044A833FC5459588F4A9184CF C41A5766
com. 86400 IN RRSIG DS 8 1 86400 20220913150000 20220831140000 20826 . R4bDq4hdjkcxxCS3hvtrd3mpkHogWQqXbi0KrvTbH0OPKdyaMOukt492 hGn710B9od8SgjfYpK2QiSCzVdv/v2PADbQzw/TgBIqldZyc3KqOdE1L vSVxX1/IqXMNqn5AiV0FOCclcmq29eSo6ayOQq2Ae/js7NEi8rYD7AvU vyOjxRqNbd8mj8bEgwbftVioQzDArLS6JBaX7xYa91z7oWbA4Ygt2R1F yCtS6A0y+OUAoXBZU22kgtQHcPEfXWJtM42KppoGtQ0dquxh4X0m++Kd nceJ7D2CWD1h1KyW7zYh5ZLzIS92spIE0s3Nv4a8eAgbKXKP0otwFxr0 SVDJQA==
;; Received 1186 bytes from 192.112.36.4#53(G.ROOT-SERVERS.NET) in 106 ms

ctrworld.com. 172800 IN NS ns-604.awsdns-11.net.
ctrworld.com. 172800 IN NS ns-457.awsdns-57.com.
ctrworld.com. 172800 IN NS ns-1029.awsdns-00.org.
ctrworld.com. 172800 IN NS ns-2045.awsdns-63.co.uk.
CK0POJMG874LJREF7EFN8430QVIT8BSM.com. 86400 IN NSEC3 1 1 0 – CK0Q2D6NI4I7EQH8NA30NS61O48UL8G5 NS SOA RRSIG DNSKEY NSEC3PARAM
CK0POJMG874LJREF7EFN8430QVIT8BSM.com. 86400 IN RRSIG NSEC3 8 2 86400 20220904042433 20220828031433 32298 com. Q8/GURHUPmV/ykhy1kMRfOyVR4SElk51JPrRU8ZNQaqSdSS6LHMibxKH mZLhMJTZKmLIQuvOLw+6r8Y/QB/g8onzYAuFILpc7Um8gAHY6tfJhO6a LHRlbYzAAvnEUlQ4ydgsE3C6/BKRw+YmalYmQTHdtbI/nEHKWJMSWWO1 cWugKBKwXk/9roUzi1dwsbdSDuhCHkurzy0/dErTk7O0lA==
HECAGUU7L8JVT2TV893GE8E12DGIV9LH.com. 86400 IN NSEC3 1 1 0 – HECANTK7NHSCOVLVD7HEDDI4RVT6UHII NS DS RRSIG
HECAGUU7L8JVT2TV893GE8E12DGIV9LH.com. 86400 IN RRSIG NSEC3 8 2 86400 20220904052128 20220828041128 32298 com. ktC8t9pvCmB/bOf0Qr6UyuP2HJ5phLK7Q9kTZMf599yfIMsZm07XNTrY IaR+lZjIbOCvbgIEEFQJYIHBKrSPgVaRo9gyg/83XGqOyLN+xo+IFAP6 q9DptpYX1fEU3B9Zkk4SyKiGbgoGWAXOXNfOjG9JqFd97E7RpJ8POZAH UxBt2cyDCaKMZX8YA6Pok7SeBy+oZixi+Vcs1yRwmACkNw==
;; Received 754 bytes from 192.54.112.30#53(h.gtld-servers.net) in 119 ms

ctrwebtest.ctrworld.com. 300 IN A 34.218.60.21
ctrworld.com. 172800 IN NS ns-1029.awsdns-00.org.
ctrworld.com. 172800 IN NS ns-2045.awsdns-63.co.uk.
ctrworld.com. 172800 IN NS ns-457.awsdns-57.com.
ctrworld.com. 172800 IN NS ns-604.awsdns-11.net.
;; Received 205 bytes from 205.251.199.253#53(ns-2045.awsdns-63.co.uk) in 5 ms

[root@ctrwebtest html]# dig -t NSctrwebtest.ctrworld.com
;; Warning, ignoring invalid type NSctrwebtest.ctrworld.com

; <<>> DiG 9.9.4-RedHat-9.9.4-74.amzn2.1.2 <<>> -t NSctrwebtest.ctrworld.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17701
;; flags: qr rd ra; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;. IN NS

;; ANSWER SECTION:
. 300 IN NS h.root-servers.net.
. 300 IN NS i.root-servers.net.
. 300 IN NS j.root-servers.net.
. 300 IN NS k.root-servers.net.
. 300 IN NS l.root-servers.net.
. 300 IN NS m.root-servers.net.
. 300 IN NS a.root-servers.net.
. 300 IN NS b.root-servers.net.
. 300 IN NS c.root-servers.net.
. 300 IN NS d.root-servers.net.
. 300 IN NS e.root-servers.net.
. 300 IN NS f.root-servers.net.
. 300 IN NS g.root-servers.net.

;; Query time: 2 msec
;; SERVER: 192.168.0.2#53(192.168.0.2)
;; WHEN: Wed Aug 31 18:48:16 UTC 2022
;; MSG SIZE rcvd: 239

You can also perform a query that returns only the name servers, as shown in the following example:

[root@ctrwebtest html]# dig -t NS ctrwebtest.ctrworld.com

; <<>> DiG 9.9.4-RedHat-9.9.4-74.amzn2.1.2 <<>> -t NS ctrwebtest.ctrworld.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43697
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;ctrwebtest.ctrworld.com. IN NS

;; AUTHORITY SECTION:
ctrworld.com. 300 IN SOA ns-604.awsdns-11.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400

;; Query time: 3 msec
;; SERVER: 192.168.0.2#53(192.168.0.2)
;; WHEN: Wed Aug 31 18:48:20 UTC 2022
;; MSG SIZE rcvd: 133

In the preceding example, http://www.ctrwebtest.ctrworld.com has the following four authoritative name servers:

ns-604.awsdns-11.net.

The following is example output for a query to http://www.ctrwebtest.ctrworld.com to one of its authoritative name servers (ns-604.awsdns-11.net). The server response indicates that http://www.amazon.com is available on 34.218.60.21:

[root@ctrwebtest html]# dig ctrwebtest.ctrworld.com @ns-604.awsdns-11.net.

; <<>> DiG 9.9.4-RedHat-9.9.4-74.amzn2.1.2 <<>> ctrwebtest.ctrworld.com @ns-604.awsdns-11.net.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12825
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;ctrwebtest.ctrworld.com. IN A

;; ANSWER SECTION:
ctrwebtest.ctrworld.com. 300 IN A 34.218.60.21 ——– > Old IP

;; AUTHORITY SECTION:
ctrworld.com. 172800 IN NS ns-1029.awsdns-00.org.
ctrworld.com. 172800 IN NS ns-2045.awsdns-63.co.uk.
ctrworld.com. 172800 IN NS ns-457.awsdns-57.com.
ctrworld.com. 172800 IN NS ns-604.awsdns-11.net.

;; Query time: 20 msec
;; SERVER: 205.251.194.92#53(205.251.194.92)
;; WHEN: Wed Aug 31 18:50:31 UTC 2022
;; MSG SIZE rcvd: 205

[root@ctrwebtest html]#

On AWS console, navigate to Route 53 -> concerned domain name (for me it was – “ctrworld.com” -> check the concerned record and edit record to change IP to new IP. Website works after this change!

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