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DNS record issue

Posted on 2011-03-23
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Last Modified: 2012-05-11
I am looking for some clarification on some DNS settings as I'm not a genius when it comes to this.

I'm specifically interested in what the @ record does and how it works.

Does this record supercede all records?

More specifically I have a site that I need to set an DNS entry in for both the www. and mail. settings.  there is an @ record for these DNS settings as well.  Each will go to a different server location and IP.

It seems that when I put a forward on for the www IP, it also affects the MX or mail. record as well.  It's the darndest thing in that when forwarding gets put on, the MX record remains the same in DNS and when pinged, but their mail goes somewhere else (don't know where).

I'm wondering if the @ record is somehow superceding the MX record and sending both?

Open for input.
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Question by:creativenetworks
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by:Chris Dent
ID: 35201568
> I'm specifically interested in what the @ record does and how it works.

@ is the Origin, you can replace it with the zone name (most of the time).

That is, in the zone "bobsdomain.com" these two are the same:

@   IN A   1.2.3.4
bobsdomain.com.  IN A  1.2.3.4

Only most of the time because the Origin can be changed within a zone. Then @ takes the new value. It's more common on the BIND side than MS or hosted solutions.

> Does this record supercede all records?

No, it's just shorthand.

> I'm wondering if the @ record is somehow superceding the MX record and sending both?

No special behaviour associated with this label.

> It seems that when I put a forward on for the www IP

What do you mean by that because DNS doesn't do Forwarding? Is it an option in some GUI?

Some DNS hosts allow you to set Forwarding, and they place this within the DNS interface which may lead to the belief that what they do is within DNS itself.

Chris
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by:Chris Dent
ID: 35201652
> the MX record remains the same in DNS and when pinged

You can't ping an MX record. You can ping a name, and the name may have some relationship with the MX record, but it doesn't really mean anything.

Perhaps you could provide a sample of what you're seeing? Naturally you should feel free to obscure any sensitive information.

You can look up an MX record, like this:

nslookup -q=mx domain.com

And from that you can see where mail would be bound for "domain.com" if a mail server were to try and send in mail. It doesn't tell you about connectivity, or how successful a delivery attempt would be, only the advertised inbound mail service.

I do wonder if the Forwarding option is changing the other records, handing off control of the domain to some DNS host. I know ours, if I were to enable the forwarding option, would render the records I've defined useless. That's why I wonder what the forwarding option you're looking at is :)

Chris
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by:creativenetworks
ID: 35204627
Chris-Dent:  >> What do you mean by that because DNS doesn't do Forwarding? Is it an option in some GUI?

Simple URL Forwarding setting from WebA.com to WebB.com in Go Daddy's Domain Manager.  Even after 24 hours the website would not forward.  Go Daddy support did not see anything unusual at their side.  And at the same time, we lost the incoming emails (from external people) on our Exchange Server. The @ record IP address would change as it does with any Forwarding I've done in the past.

We are hosting our own email on Exchange server within our company.

Chris-Dent: >> And from that you can see where mail would be bound for "domain.com" if a mail server were to try and send in mail. It doesn't tell you about connectivity, or how successful a delivery attempt would be, only the advertised inbound mail service.

When doing nslookup, the primary name server is "ns33.domain1.com"; responsible mail addr is "dns.webc.net" for instance.

Chris-Dent: >> I do wonder if the Forwarding option is changing the other records, handing off control of the domain to some DNS host. I know ours, if I were to enable the forwarding option, would render the records I've defined useless. That's why I wonder what the forwarding option you're looking at is :)

We will have to do this again over the weekend to check if other records "A" or "MX" for instance are changing as well as the main @ record by just setting the URL Forwarding.

It makes me wonder if the company where the website is truly "hosted" at has a setting that needs to be changed.  One thing the Go Daddy tech said that the website we have live is on a Windows web server.  So that may make a difference in making a change to the record on the hosting company server.
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by:Chris Dent
ID: 35205530

> One thing the Go Daddy tech said that the website we have live is on a Windows web server.  So that may make a difference in making a
> change to the record on the hosting company server.

Shouldn't have any effect really.

I suspect the web forwarding option is wiping out some of the other entries. If that is the case you have a few choices:

1. Reconfigure the web server to accept traffic on http://www.yournewdomain.com and http://yournewdomain.com

If your current solution is based in a shared hosting environment this means a modification on the web server so it knows what to do when it is presented with a request for yournewdomain.com.

2. Forward via a third-party

Forwarding via a third-party means you would have to run, or find someone to run, yet another web server. Then you have that web server forward on the request.

It's important to realise that forwarding is a web server operation, not a DNS operation. Them exposing a setting like that means they're taking over your www and @ records (should be A records only, not MX, although it's not uncommon for them to take everything), pointing things to their own web server, and having that forward for you.

Chris
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Author Comment

by:creativenetworks
ID: 35223542
Here's what I'm dealing with.

I have two url's d1.com and d2.com.  d1.com point to the live/correct site.  d2 uses the URL where their mail is held.  I need @ and www on d2 to point to d1 and need the mx to point to a 3rd server.

is this even possible?

I am forwading d2 to d1 and have an MX and cname record for the mail server but it doesn't seem to be working.

Any help would be greatly appreciated
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Accepted Solution

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Chris Dent earned 2000 total points
ID: 35230456
Sure, that's fine. We might have:
@ IN A  1.2.3.4
@ IN MX 10 mail

www  IN CNAME @
mail IN A  1.2.3.5

Open in new window

In our example, @ can be replaced with "d2.com.".

Here we're saying that clients asking for d2.com, or www.d2.com will get 1.2.3.4 (which should be the IP for d1). And anyone wanting to deliver mail will be instructed to use mail.d2.com, ending up with 1.2.3.5 (which should be your third server).

So far so good. Now we only have to deal with the term "Forward". You don't get forwarding, this is important if you expect this to happen:

1. User types www.d2.com into the address bar in IE
2. URL is changed to www.d1.com
3. Content comes from 1.2.3.4 (d1 IP) using the name www.d1.com

Instead, what will happen is this:

1. User types www.d2.com into the address bar in IE
2. Content comes from 1.2.3.4 (d1 IP) using the name www.d2.com

This is intended to highlight the importance of the web server. It must be willing to respond as www.d2.com. If it does not, or can not, you'll have to find another web server that can, and forward or redirect from there.

Does that make sense?

Cheers,

Chris
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