DNS record generator

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#1 Sat, 03/29/2008 - 16:19

DNS record generator

Does anyone have an example for the format we need to use in the DNS record generator? I'd like to have it generate a bunch of w.x.y.z.mydomain.com records so that each of my clients has a valid DNS and reverse dns entry.

I've looked for examples, but failed so far.

Mon, 04/21/2008 - 12:12

I've been told by our ISP that any one IP can only have one reverse record which means that only one domain can have a RDNS record.

I don't know this to be true for sure but it kind of makes sense unless somehow the reverse lookup returned all the possible domains at the IP.

Tue, 04/22/2008 - 00:27 (Reply to #2)
Joe's picture

If you think about it, it's pretty obvious that any given IP can only have one reverse record.

What's the reverse of example.com. Not what's the reverse of Still example.com. It's never gonna change because the query is always "what's the reverse of"

The good news is that reverse records don't matter. You just need to have one for each IP that you intend to send mail from. It doesn't need to match any of your forward records (so virtualmin.com can, and does, have a reverse of ee.4.5646.static.theplanet.com and it works fine), it just needs to exist.

But, of course, if you actually have one IP per customer, you could do that...but you're not going to be able to convince Postfix to send out on a different IP address based on the sending user (and there's no reason to do so).

Record Generators are discussed here in the Webmin documentation:



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Sun, 01/18/2009 - 11:44 (Reply to #3)

Yes URL is the Domain.

VM is where my DNS is hosted; the NS records for Glue at GoDaddy Seem to be working fine; but I have no Reverse DNS.

I'm only using GoDaddy as Glue; its this domain I'm wondering about; do I add the reverse here or at my VM site; if VM do I use the Record Generator to do that; which was why I'm looking for the format; but since the site is down, I can use a little help.

I'm just trying to get the Email Server to work.

Its a Linux CentOS (Latest) server with VM Pro; I added the A records for NS1 and 2 and host records at GD, with the .net TDL; which will not have email; so this URL will only act as Glue and also host a web site. I have many more sites all using 1 IP address; and want most of them to have Email for each Domain.

Thanks Jeff

Jeffrey Scott Flesher
Medically Retired Gulf War Vet

Sun, 01/18/2009 - 12:11 (Reply to #4)

Could I add a PTR to get reverse DNS like this:

Change this
domain.org. IN TXT "v=spf1 a mx a:domain.org ip4: ?all"
To this
domain.org. IN TXT "v=spf1 a mx ptr a:domain.org ip4: ?all"

Reading documents on DNS is very difficult for me now a days; its mind numbing on a good day.

Jeffrey Scott Flesher
Medically Retired Gulf War Vet

Sun, 01/18/2009 - 13:53 (Reply to #5)
Joe's picture

Doxfer is back up. I'm looking into why it went down. It'll all be merging into one site in the not too distant future, so the Webmin docs won't be off in the ghetto of another website and server forever (and we notice fast when Virtualmin.com or Webmin.com go down!).


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Tue, 01/20/2009 - 19:24 (Reply to #6)

<div class='quote'>Could I add a PTR to get reverse DNS like this:</div>

Sorry, no :-)

The only way to get reverse DNS setup is to go through your ISP.

As the DNS administrator on your server and the domain owner, your job is the forward DNS. Making example.com resolve to x.y.z.q.

The ISP's job, as the owner of your IP address, is to provide reverse DNS -- making x.y.z.q resolve back to example.com.

Sun, 03/15/2009 - 07:15 (Reply to #7)

Thanks Joe, you answered my question with the link you provided. I could not find that info in the documentation when I looked.

As for multiple reverse DNS and my ISP, well, I <i>am</i> the ISP and have my own IP block assigned directly from ARIN. I did not look forward to generating 1000 addresses and reverse addresses manually....


1.z.y.x.lucketts.net. x.y.z.1 &amp; its reverse
2.z.y.x.lucketts.net. x.y.z.2 &amp; its reverse
.... etc

Many of my clients have their own mail servers which need a reverse DNS assigned by their ISP to work properly (thats me)


Sun, 03/15/2009 - 09:45 (Reply to #8)

OK... Joe didn't completely answer my question. His link gives instructions that when followed produce invalid DNS records for a normal domain. But it demonstrated the basic syntax, so I was able to figure out how to make it work.

If you have a domain named test.net and you want to automatically generate resolvable DNS and reverse DNS names for IPs x.y.z.17-254, here are the settings:

In the master zone generator:
Type Range Address pattern Hostname pattern
A 17 - 254 $.z.y.x.test.net. x.y.z.$

In master reverse zone generator:
Type Range Address pattern Hostname pattern
PTR 17 - 254 $.z.y.x.in-addr.arpa. $.z.y.x.test.net.

This will produce successful DNS lookups for
x.y.z.17-254 mapping to 17-254.z.y.x.test.net and vice versa.

You can also just enter the instructions into the records file. Here is my entries to produce client IP addresses at lucketts.net. I first generated a subset domain called static.lucketts.net and its reverse so that my main domain file would not be messed with.

Master zone records file:
$generate 17-254 $.86.82.208.static.lucketts.net. A 208.82.86.$

Reverse zone file:
$generate 17-254 $.86.82.208.in-addr.arpa. PTR $.86.82.208.static.lucketts.net.

The lines in the records file will show up in the records generator to demonstrate the proper format. I can now nslookup and get as an answer, or I can nslookup and get as an answer, and I didn't have to manually enter 240 addresses by hand to have this work for the larger range.

Hope this helps someone else.


Sun, 01/18/2009 - 11:05

Last few days doxfer.com has been down; what's up?
Do you have another URL?

I only have one IP address; I setup VM Pro as a DNS Server; it has no Reverse Record; so I need to make one; question is where and how. I have 30 Sites in VM; I would like most of them to have their own Email; do I only setup one or do I have to setup one per URL?

I have my URLs from Godaddy (GD); I set it up correct; I think; I am keeping one URL hosted on GD's DNS server to point to my DNS server; is that right?

Jeffrey Scott Flesher
Medically Retired Gulf War Vet

Sun, 01/18/2009 - 11:21 (Reply to #10)

Indeed, doxfer does appear to be down, hopefully Joe can kick that back up again :-)

Reverse DNS records would be setup through your ISP/hosting provider.

Generally, you would have one reverse DNS record per IP address.

When you say &quot;URL&quot;, I assume you mean &quot;domain&quot;.

Personally, I register my domains using GoDaddy, but my DNS and such are all hosted from my own servers -- GoDaddy isn't hosting DNS for any of my domains.

I do use GoDaddy in order to register two of my IP addresses as glue records / nameservers, but it's the servers running Virtualmin that are hosting all of the DNS for my domains.

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