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nitefox 15th June 2007 03:42

Reverse DNS Problem
 
Several months ago I followed the Perfect Setup for Ubuntu 6.06 and installed ISPConfig. Everything was working wonderfully until a few days ago when the majority of the email sent from my server started being bounced back due to reverse DNS lookups failing. I confirmed with www.dnsreports.com that the reverse DNS does in fact fail.

I contacted my ISP about adding reverse DNS for my net block. I currently have a /29 IP block with 5 IPs. 2 of these IPs host my local nameservers through ISPConfig, however one is a dummy. My ISP said they are adding my reverse DNS entries today, but I need to make sure my zone files are configured properly. According to them, the zone reference in /etc/bin/named.conf should look like:

zone "xxx-29.xxx.xxx.xxx.in-addr.arpa"

However my ISPConfig-generated /etc/bind/named.conf reverse DNS entry looks like:

zone "xxx.xxx.xxx.in-addr.arpa" {
type master;
file "pri.xxx.xxx.xxx.in-addr.arpa";
};

EG it stops with the class C address, and does not directly reference the start IP of my /29 block. Within the pri.xxx.xxx.xxx.in-addr.arpa file, everything has been generated by ISPConfig, and it looks correct. Each PTR entry is preceded by the final octet of data that defines the IP address of the DNS server.

My question is... is my ISP correct about the naming convention for the zone entry in named.conf? I would rather not change it, as I have a feeling when ISPConfig restarts it will create the entry as it sees fit.

Thank you in advance for any advice/pointers.

till 15th June 2007 12:13

It should work the way ISPConfig creates the zone files. Please wait until your ISP has changed his records and the changes have been proagated and thesn test if everything works.

nitefox 16th June 2007 08:26

They successfully added the reverse DNS entry this morning, and now www.dnsstuff.com shows a response from the server, however the response indicated no PTR records exist. I believe this is because my ISP is referring the query to the correct server, but the zone. As indicated in the reverse DNS trace, the zone that is being referred to is formatted as:

yyy.subnetxxx.xxx.xxx.xxx.in-addr.arpa.

Where yyy is the final octet in the IP address of the ISPConfig DNS server, and xxx.xxx.xxx.xxx is the reverse of the IP of the start of my /29 IP block. So from this information, it looks like I will need to manually chage the name of the zone entry in named.conf.

So I changed the name of the entry in named.conf manually, restarted bind, and now the zone entry is shown as valid. However the server being queried is my dummy nameserver... and it is responding with NODATA.

So two questions if I may. I have 2 NICs on that machine but only one instance of ISPConfig and bind running, so I can only run one nameserver. What is the best way to handle having to run two nameservers on the same machine?

Second question: If I want ISPConfig to call the reverse DNS zone entry something different, where do I go about modifying that?

Thanks again for all the help.

mlz 16th June 2007 10:34

Technically, it's an RFC violation to run two name servers (primary and secondary) on one machine. However both ips should be answering NS queries in a standard setup (i.e. 1 machine with two nics, or multiple ip address').


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