Setting up Private DNS in google cloud

0
votes

2 years back Google introudced private DNS which is very important for internal domains communication.

I setup a private dns to learn about DNS using below documentation guide https://cloud.google.com/sdk/gcloud/reference/dns/managed-zones/create https://www.jhanley.com/google-cloud-private-dns-zones/

Below are the steps followed to create an example zone

Created a private zone "private-zone"

gcloud dns managed-zones create --dns-name="example.com" --description="Private Zone" --visibility=private --networks=default "private-zone"

Then created a vm in google cloud and ran the nslookup for the domain name. But it did not resolve

testdns:~$ nslookup example.com
Server:         169.254.169.254
Address:        169.254.169.254#53
Non-authoritative answer:
*** Can't find example.com: No answer

I'm using Debian OS on the Vm instance created

Linux testdns 4.19.0-12-cloud-amd64 #1 SMP Debian 4.19.152-1 (2020-10-18) x86_64 GNU/Linux

These are two A records other than NS and SOA records in

test.example.com.   A   300  192.0.0.9
www.example.com.    A   300  192.0.0.91
example.com.        A   3600 192.0.1.1

Below example was tested

nslookup when "example.com" A record was not added

mymach@testdns:~$ nslookup example.com ns-gcp-private.googledomains.com
Server:         ns-gcp-private.googledomains.com
Address:        169.254.169.254#53
Non-authoritative answer:
*** Can't find example.com: No answer

#dig example.com using nameserver , 'A' record was added

testdns:~$ dig example.com @ns-gcp-private.googledomains.com
; <<>> DiG 9.11.5-P4-5.1+deb10u2-Debian <<>> example.com @ns-gcp-private.googledomains.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 41534
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;example.com.                   IN      A
;; ANSWER SECTION:
example.com.            3600    IN      A       192.0.1.1
;; Query time: 12 msec
;; SERVER: 169.254.169.254#53(169.254.169.254)
;; WHEN: Tue Dec 08 23:03:58 UTC 2020
;; MSG SIZE  rcvd: 56

nslookup again after adding example.com

testdns:~$ nslookup example.com ns-gcp-private.googledomains.com
Server:         ns-gcp-private.googledomains.com
Address:        169.254.169.254#53
Non-authoritative answer:
Name:   example.com
Address: 192.0.1.1

dig

testdns:~$ dig example.com 
; <<>> DiG 9.11.5-P4-5.1+deb10u2-Debian <<>> example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24673
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;example.com.                   IN      A
;; ANSWER SECTION:
example.com.            3600    IN      A       192.0.1.1
;; Query time: 11 msec
;; SERVER: 169.254.169.254#53(169.254.169.254)
;; WHEN: Tue Dec 08 23:06:30 UTC 2020
;; MSG SIZE  rcvd: 56

dig using local host

dig example.com @127.0.0.1
; <<>> DiG 9.11.5-P4-5.1+deb10u2-Debian <<>> example.com @127.0.0.1
;; global options: +cmd
;; connection timed out; no servers could be reached

Am I missing some step ?

1
google-cloud-platformdnsnslookupgoogle-cloud-dns
Did you modify /etc/resolv.conf or make any other DNS or DHCP changes to the instance that you are running this command on? What do you expect example.com to resolve to? Unless you have created DNS Resource Records, example.com does not have anything to return. – John Hanley
@JohnHanley; Thanks for responding, I did not modify resolv.conf file I do expect this to give me an IP I got as part of private domain setup in A record – Learner
Edit your question with details on the A records. Also are you actually using example.com or is this just a placeholder? Which OS and version? Post the output of this command nslookup example.com 127.0.0.1 – John Hanley
Go to the Google Cloud Console -> Network services -> Zone details. Lookup the value for the NS resource record. Replace NS_VALUE with that value in this command: nslookup example.com NS_VALUE. Post that output in your question. – John Hanley
That is now how things work with DNS or with web browsers. When you type example.com in a web browser and the browser then displays www.example.com that is because of an HTTP redirect by the web server, load balancer, etc. If you resolve example.com it will only resolve example.com. I am ignoring wildcards. – John Hanley

1 Answers

1
votes

After you created your zone with:

gcloud dns managed-zones create --dns-name="example.com" --description="Private Zone" --visibility=private --networks=default "private-zone"

You must create DNS registries to it, for example:

gcloud dns record-sets transaction start --zone="private-zone"
gcloud dns record-sets transaction add 10.2.3.4 --name="example.com" --ttl="3600" --type="A" --zone="private-zone"
gcloud dns record-sets transaction execute --zone="private-zone"

Give GCP 1 minute to catch up, and then try again with the default "/etc/resolv.conf" file.