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We are a new ISP and one of our recent clients has an email server behind our public IP and is requesting rDNS from us, We own a /21 prefix, and we give our client a /29 prefix for their services. I did some research and found out that We as an ISP are responsible to do rDNS but I simply can't find much information as to how this is setup.

I have created a bind9 server as a test and created a test zone with reverse zone which is working fine locally but how do I set this up without messing with the domain of our clients

I'll really appreciate your help.

Regards,

EDIT: After a while finally got it working, thank you for the guidance and information. Regards.

aromeromex
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1 Answers1

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There is no relationship between rDNS and the customer's regular DNS domains.

Reverse DNS for your IP address range is delegated through the IP address registry. For example, if you have an inetnum with RIPE you would create a domain object in the RIPE DB, named after the rDNS zone, and point its nserver: attribute to your nameservers that are hosting the zone – altogether very similar to delegating a regular DNS domain. Other RIRs (ARIN, APNIC etc) may have similar procedures.

domain:   5.168.192.in-addr.arpa
nserver:  ns1.example.net

Since you have a /21 you may need to repeat this for each of the eight /24 zones (z.y.x.ip-addr.arpa), or start with just the one /24 which has your customer.

Once the rDNS has been delegated to you, you can either directly set up PTR records for your customer or use various approaches to further delegate the /29 chunk to the customer's own nameservers. (A whole /24 is exactly at DNS 'dot' boundary so it can be delegated with just NS records, but below /24 it gets slightly ugly.)

grawity
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