Delegating Reverse Lookup Zones for big subnets

Imagine that your company’s network owns the IPv4 range 40.50.60.0 – 40.50.60.255. The Reverse Lookup zone would be 60.50.40.in-addr.arpa, covering this entire network. Your primary nameserver is ns.acme.com. Your zone would look something like this:

60.50.40.in-addr.arpa       ns.acme.com.      support.acme.com. (
                                              20111202001
                                              4h
                                              1h
                                              1w
                                              1h
                                              )

@          IN          NS           ns.acme.com.
1          IN          PTR          www.acme.com.

But now you want to delegate the range 40.50.60.20 – 40.50.60.39 to the nameserver coyote.acme.com. Since it also resides in the same reverse zone, you cannot delegate this entire zone, as this would just move your entire network to the control of coyote.acme com, something you might not want to achieve with delegation.

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