Reverse delegation along classless lines works somewhat differently than reverse delegation along classful lines. Address Manager follows the methods described in RFC 2317 Classless IN-ADDR.ARPA delegation.
To illustrate, suppose you host the reverse DNS zone for the 192.168.1.0/24 network on a DNS server and you need to delegate the 192.168.1.128/25 network to a different DNS server. From the Address Manager user interface, the procedure is no different from classful delegation as described in Delegating reverse zones. However, the format of the zones on the DNS servers is quite different. The following example assumes that the default reverse zone name format: [start-ip]-[net-mask].[net].in-addr.arpa is used.
- A zone named 128-18.104.22.168.in-addr.arpa is created on the child DNS server.
- A delegation record (NS) for the 128-22.214.171.124.in-addr.arpa zone is created on the parent server.
- CNAME records for every possible delegated PTR record are created on the parent server.
To delegate a classless reverse zone:
- Create an IPv4 block with a 24-bit prefix.
- Assign a deployment role to the parent server at the block level.
- Create a classless network (25-bit prefix for example).
- Assign a deployment role to the child server at the 25-bit network.
- Deploy the configuration.