Reverse Name Service (PTR Records)

Issue 1

Contact your service provider or the company that gave you your IP numbers, ask them to set up reverse name service.

Server is a Google Cloud Compute instance.

The tutorial on google cloud https://cloud.google.com/compute/docs/instances/create-ptr-record talks about verifying the domain name... as part of that process it asks for one to place a verification file on the server webspace.

How am i supposed to do that exactly? (This server doesnt have its own website, its used as a hosting platform for other client websites). Am i supposed to setup a website for the server so google can verify i own the domain?

Issue 2
Also, just want to have someone check the following is correct...i read somewhere about ip address. Should it be included in the hosts file?

when i enter hostname -f
it returns server3.mydomain.com

/etc/hosts file is as follows...
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

xx.xxx.x.x server3.mydomain.com.au server3
#xx.xxx.x.x server3.c.googlename-1.internal server3 # Added by Google
xxx.xxx.xxx.xxx metadata.google.internal # Added by Google

Issue 3
Finally, my server doesnt have any file called /etc/hostname. Should i create one?

 

Issue 1
I do not know how google service works. Other services allow many ways to prove domain ownership. For example by adding a TXT record to DNS.
Issue 2
Check what?
Issue 3
What operating system? The systems I am familiar with do have /etc/hostname.

 

Issue 1
I do not know how google service works. Other services allow many ways to prove domain ownership. For example by adding a TXT record to DNS.

so would this record have to be

mydomain.com TXT 3600 "v=spf1 a mx a:mydomain.com ip4 <server network ip address> ip4 <server public ip address> ? all"

Or should it be

server3.mydomain.com TXT 3600 "v=spf1 a mx a:server3.mydomain.com ip4 <server network ip address> ip4 <server public ip address> ? all"

or should it be something else?

Issue 2
Check what?

Whether or not i should add the server public ip address into the file

Issue 3
What operating system? The systems I am familiar with do have /etc/hostname.

The webserver is Debian 9
I forget now how i setup this server, but I am assuming it is getting its hostname from somewhere other than /etc/hostname?

 

Issue 1
IF Google verifies by TXT record in domain, it tells you what record to add there. It is usually a random string.
Issue 2
You crossed out the IP-numbers in the file you showed. My guess was the IP number was there already. If you change the IP number the host has, write the new number there.
Read

Code:

man hosts

Issue 3

Code:

man hostname

states among others that

 

oh yes...ip address was already there but the ip addresses that i have crossed out in the hosts file are the google cloud internal network ones. (ie not public ip addresses).

Could i simplify this a little...

1. should i have public ip address in hosts file?
2. does the dns A Record at registrar need to be <server3.mydomain.com> or can i leave it as it is <mydomain.com> ?

 

1. should i have public ip address in hosts file?
Yes.
2. does the dns A Record at registrar need to be <server3.mydomain.com> or can i leave it as it is <mydomain.com> ?
Best is to have both. That is, two A records, one for the domain and one for the host.

 

ah ok...i need to add some extra information into hosts file, and also an additional A record for server3.mydomain.com (currently it does not have this)

Could i also ask about the following...
according to google webmaster tools (webmaster central) https://server3.mydomain.com/ is verified. (result "verification succeeded via HTML file")

In google cloud console, i go to vm instance> Edit> Network interface> Enable Public DNS PTR Record and attempt to add PTR domain name <server3.mydomain.com>

It returns an error....
Editing VM instance "server3" failed. Error: Invalid value for field 'resource.publicPtrDomainName': 'server3.mydomain.com.'. Please verify ownership of the PTR domain at https://www.google.com/webmasters/verification/verification?domain=server3.mydomain.com.

I dont understand the error...the domain is verified. What does it mean by invalid value "server3.mydomain.com"

This is what google cloud help says on how to do this...

1. Go to the VM instances page.
   
2. Click the instance you want to edit.
3. Click the Edit tool from the top menu.
4. Click the edit tool next to the primary network interface.
5. Click External IP drop down menu.
6. Configure your External IP to enable PTR Record.
7. Check the Enable box for Public DNS PTR Record.
8. Enter your domain name.
9. Click Done.
10. Click Save at the bottom of the page to save your settings.

 

I don't know about Google tools. And I don't know what server3.mydomain.com really is. So no comment.
Try mxtoolbox.com or https://tools.pingdom.com/ or some such to check your setup.

 

i have started a conversation with you. my server domain is in that. The website that comes up in pingdom.com is not actually the server page.. server3.mydomain.com doesnt have a website associated with it so apache is just throwing up the first one in its list (I havent got around to creating a default page or a redirect page for the server yet)

 

I have just found this...https://sendgrid.com/docs/glossary/spf/

i wonder if because google cloud has all mail ports blocked, and therefore i am using sendgrid, perhaps this is a workaround?

I am assuming i do this at my external dns host (which in my case is the domain registar)

Question
should i add an "additional txt record" for server3.mydomain ( server3.mydomain.com txt 3600 "v=spf1 a mx:mydomain.com...") or,

just add the sendgrid entry to the existing entry in mydomain.com txt "v=spf1 a mx a:mydomain.com ip<reverseip> ?all" ?

from what i can see in my registrar console, whmcs has its own txt "v=spf1 a mx..." records for each subdomain (ie billing.mydomain, whmcs.mydomain, buy.mydomain)

 

For SPF, there are also
https://www.spfwizard.net/
and
http://www.openspf.org/Tools
Let the wizard make the TXT record, then it works.
What workaround are you hoping for? I mean, a workaround for what?

 

the google cloud reverse ptr value i am inputting being rejected as invalid.

I have gone to the spfwizard.net website you provided the link to.

I notice that it is asking for the mail server/relay host ip address...

google Cloud Compute requires us to use a third party mail relay host for all outgoing mail on standard ports. I am filling out the spf wizard as you suggest.
I am not sure about one thing.

should the ip address in cdir format be public? the examples shown when i hover my mouse over this box are private ones ... ie 10.0.0.1/32 or 192.168.0.1/28 (see image file attached...)

also,
according to sendgrid tutorial https://sendgrid.com/docs/ui/account-and-settings/how-to-set-up-reverse-dns/ , my dns provider can also be a place for setting up reverse dns. That is the avenue i am going to explore.

 

OMFG...i have figured it out!

Ok so here is what i had to do to get this working...

1. Go to Google Webmaster Central> domain verification - "Alternate method"> domain name provider (then copy the txt record it provides to your domain DNS zone records). once verified then,

2. In google cloud console>vm isntance> Edit instance> nic0 > public DNS PTR Record > add your "domain.com" (exactly as shown in the verification result)

voila, The PTR input value in Google Cloud Compute is now sorted!

Now on to the next issue at the top of the list... (I am making progress). My assumption is that this is because i need to input server3.mydomain.com into Google Cloud "Public DNS PTR Record" instead of mydomain.com?

SMTP Valid Hostname Reverse DNS is not a valid Hostname More Info
SMTP Reverse DNS Mismatch OK - xx.xxx.xx.xxx resolves to mydomain.com
SMTP Banner Check OK - Reverse DNS matches SMTP Banner
SMTP TLS OK - Supports TLS.
SMTP Connection Time 1.988 seconds - Good on Connection time
SMTP Open Relay OK - Not an open relay.
SMTP Transaction Time 4.694 seconds - Good on Transaction Time

 

yep that sorted it...just needed to change the Google Cloud Public DNS PTR Record to server3.mydomain.com and mxtoolbox now seems to be happy in that the test for ip address now is ok for smtp hostname.

SMPT:xx.xxx.xx.xxx (server3.mydomain.com IP Address)

SMTP Reverse DNS Mismatch OK - xx.xxx.xx.xxx resolves to server3.mydomain.com
SMTP Valid Hostname OK - Reverse DNS is a valid Hostname
SMTP Banner Check OK - Reverse DNS matches SMTP Banner
SMTP TLS OK - Supports TLS.
SMTP Connection Time 1.720 seconds - Good on Connection time
SMTP Open Relay OK - Not an open relay.
SMTP Transaction Time 4.387 seconds - Good on Transaction Time

 

Nice job. I still haven't fixed PTR for my dns servers yet. Hopefully I can resolve it soon.

 

Its not connection can anyone help again

 

You should not hijack 4 year old threads.
You say "again". When was the previous time?