Reverse DNS and PTR Records

L

lodp

Verified User
Joined
Sep 30, 2007
Messages
11
Hi everyone,

It was suggested to me that I should get reverse DNS lookups set up properly.

After reading up a bit here on the forums, I turned to my ISP, who said they were going to get it set up, and the changes would become effective within 24-72h.

But the DNS configuration I'll have to do myself. So here's the thing. Do I have to add a PTR record for the domain in question now in DirectAdmin?

thanks for your help
 
No, you can't add a PTR record in a domains DNS config.

Each IP address that your ISP gives you can only have a single PTR record or name.domain.com associated with it.

Unless the ISP delegates the reverse dns to your server (usually they won't)they will maintain the PTR zone's themselves. You just need to tell them what you want each IP to resolve to (e.g. mail.main-server.com, name.main-server.com).
 
Well, I suppose I'll have to let my ISP handle this then.

Here's what I don't understand. There's only one single IP address assigned to the server, but there's several domains hosted there. Now if the ISP does it properly, that IP is going to reverse-resolve to just one of these domains. Doesn't that get the other domains in trouble, in that reverse-dns for them resolves to a different domain?
 
The rDNS is mostly for email. Does not matter for shared web hosting.

All email for all domains goes out as the main host.domain.tld that you setup when you installed the server. Set the PTR to that.

If you don't know what your email server announces its self as telnet to port 25 of your server and it will show you.

telnet yourdomain.com 25
 
The response I got in the telnet connection was host.domain.tld, where domain was one of the domains on the server.

So the ISP probably set the rDNS to host.thatdomain.tld? i guess i don't need to add a PTR record for host.thatdomain.tld in DA then?

The rdns lookup on dnsstuff still says:

<My Server IP> PTR record: <some.seemingly.phony.long.string.la.> [TTL 28800s] [A=<IP that the phony string resolves to>]

*ERROR* A record for <some.seemingly.phony.long.string.la> does not point back to original IP (A record may be cached).
Click to expand...

I guess the changes just haven't propagated yet...

Thanks for your help, I much appreciate it.
 
Last edited:
lodp said:
The response I got in the telnet connection was host.domain.tld, where domain was one of the domains on the server.

So the ISP probably set the rDNS to host.thatdomain.tld? i guess i don't need to add a PTR record for host.thatdomain.tld in DA then?
Click to expand...

The response you get from telnet is not pulled from rDNS. Its pulled from the hostname of your server as defined in DA under Administrator Settings - Server's Hostname and found in /etc/hosts. If that is set to a customers domain name, I would suggest change it to one of your own.

The rdns lookup on dnsstuff still says:

I guess the changes just haven't propagated yet...

Thanks for your help, I much appreciate it.
Click to expand...

Once you make sure your hostname is set correctly and exim is responding with it I'd send the ISP an email asking to change the PTR for your IP to the one that exim reports.
 
The hostname is set to host.one-of-my-own domains.tld. So I didn't have to change that.

My hosting company handles the whole thing with the ISP (or ARE they the ISP?).

I told them I needed rDNS working with one of the domains (which is not the one in the hostname), -- I suppose they'll have the PTR set to my host name (the one I get by telnet 25 on the single IP the server has).

So, as soon as the has propagated, I should see my host name as a result in an rDNS lookup on dnsstuff.com, right?
 
I wouldn't assume they are going to set the PTR to one of your host.domains unless you tell them what to set it to. Technically rDNS is working if it returns <some.seemingly.phony.long.string.la>. Its just not returning the result you were assuming they would set it to.

The TTL on that record is set to 8 hours. It shouldn't take more than 8 hours for a change to be seen.
 
Without having real information it's impossible to do anything but guess; lodp, either tell us your real server information or just work this out with your ISP.

The problem with <some.seemingly.phony.long.string.la> is that to some aggressive MTA administrators, it looks like a dialup IP# and they won't accept email from it.

Jeff
 
thanks for your help, guys.

it seems that after more than a week the ISP finally set it up right, the rDNS now resolves to my server's hostname. the lookup on dnsstuff doesn't show any errors. i'm happy with that. thanks again!
 
You must log in or register to reply here.
Back
Top