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Reverse DNS Question (PTR)

Posted on 2004-08-04
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Last Modified: 2012-06-27
I host my own DNS. I have multiple Domains. All domian mail are hosted on one server and all domains web are on another server. I beleive I have the forward lookup zones correct. My question is on Reverse look up zone. I have the zone create and I am adding pointer records. Can I have multiple pointer records (for different domins example: www.domain1.com and www. domain2.com ) point to the same IP address. Also the same for mail pointer records. (I am on windows 2003) For instanse

1.2.3.4                  PTR                  www.domain1.com
1.2.3.4                  PTR                  www.domain2.com
1.2.3.5                  PTR                  mail.domain1.com
1.2.3.5                  PTR                  mail.domain2.com
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Question by:ryancaroll
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Expert Comment

by:JamesDS
ID: 11717820
ryancaroll

Forward lookups resolve a name to an ip and you can have multiple names (cnames) assigned to the same IP, but only one host.

Reverse lookups resolve an IP to a name and you can have multiple cnames assigned to the same host.

You can also have the same IP assigned to multiple hosts as per your list, but you will have to use round robin to get any benefit from doing this.

Enable round robin in the DNS Server properties on the advanced tab.

Cheers

JamesDS
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Expert Comment

by:DeanHarris1
ID: 11717833
Hi,

This should help:

"Basically the principle is the same for all, you point the DNS records for all websites to one IP and setup host headers in the webserver, so basically the webserver receives all requests and determines what website to server based upon the host header passed to it.

www.siteone.com 192.168.0.1
www.sitetwo.com 192.168.0.1

192.168.0.1 webserver looks at the host headers and serves the site.

Look up virtual hosts in your webserver documentation, it will give you a detailed explanation."
(taken from http://www.experts-exchange.com/Web/Web_Servers/Q_21025503.html)

and mail

"Basically, no.  Incoming traffic will all be pointed to port 25 (SMTP) of a single IP address, and that will either be answered by a single process on a single host, or distributed across multiple hosts by a load-balancer that is unaware of the domain names in the To: addresses.

You *may* be able to configure serverA to forward all mail for domainB to serverB, but as long as the MX record for domainB points to serverA, serverA will at least receive all of domainB's mail, even if it doesn't keep any of it."
(Taken from http://www.experts-exchange.com/Networking/Q_21002592.html)
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Author Comment

by:ryancaroll
ID: 11718014
James DS

My forward zones if configured like this

siteone.com
(same as parent folder)        Mail Exchanger(MX)                       mail.siteone.com
www                                   Host(A)                                         1.2.3.4
mail                                     Host(A)                                         1.2.3.5


sitetwo.com
(same as parent folder)        Mail Exchanger(MX)                       mail.sitetwo.com
www                                   Host(A)                                         1.2.3.4
mail                                     Host(A)                                         1.2.3.5



My reverse is like this:


1.2.3.4                  PTR                  www.domain1.com
1.2.3.4                  PTR                  www.domain2.com
1.2.3.5                  PTR                  mail.domain1.com
1.2.3.5                  PTR                  mail.domain2.com


I have Round Robin enabled. With this config should everything work fine.  Is there anything else I need to do? Anything to add?
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LVL 16

Expert Comment

by:JamesDS
ID: 11718813
ryancaroll
I just tested that config here and while I can't test the email bit (see DeanHarris1 comment) it seems to function properly for the www entries.

Setting priroties on your MX records will give you a measure of fault tolerance, but you won't get load balancing on email systems without a proper load balancing setup, which needs more than just a few additional DNS entries.

You will need to do some testing for yourself methinks :)

Cheers

JamesDS
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Author Comment

by:ryancaroll
ID: 11720112
So everything looks good on the reverse lookup config?

Thanks both of you for your time. You have been a big help!
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Accepted Solution

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JamesDS earned 375 total points
ID: 11723408
ryancaroll
Welcome, glad to help

Cheers

JamesDS
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Author Comment

by:ryancaroll
ID: 11729586
Ok, i found one problem sbc was hanleing reverse delegation (which was not working because of old info) I am handleingit now. Now I have my pointer records set up in DNS but when i go to www.dnsstuff.com and put in my ip address it comes back and tells me that my name servers don't return any PTR records. Please help, i can't figure it out
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LVL 16

Expert Comment

by:JamesDS
ID: 11733497
ryancaroll

It sounds like you are not the authority for your DNS zone. Are you sure the lookup is being performed at your DNS Servers?

Cheers

JamesDS
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