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The subnet being delegated to the Customer Site is the second range, that is the 64 network using 65-126 for the host IP addresses. Here is the example we will use of an ISP who has taken a Class C range and subnetted it into four subnets by using the 255.255.255.192 subnet mask. The checklistįilling out the following checklist will make walking through this document easier. Whichever syntax is chosen in the Parent domain MUST be identical to the syntax used in the Child domain. This indicates that the subnetted reverse lookup zone is the 64 subnetwork that is using 26 bits for its subnet mask. (where X is the subnet number assigned by parent) orįor example: or When creating classless reverse lookup zones, you may use notation such as the following ones: Because the ISP scenario is most typical, it will be used in the following example. Common configurations involve an ISP (Parent) delegating to a Customer Site (Child) or a Corporate Headquarters (Parent) delegating to a Corporate Remote Site (Child). Therefore, from the example above, we know that: If the subnet mask isĭelegated subnetted reverse lookup zones can be used to transfer administrative control between any parent and child IN-ADDR.ARPA zone in the DNS. This is defined by adding additional bits to the subnet mask. When subnetting IP networks, additional bits are taken from the host portion of the IP address and given to the network portion. For example, a class C address of 192.168.1.0 with a subnet mask of 255.255.255.192 is a classless IP addressing scheme. For example, a class C address of 192.168.1.0 with a subnet mask of 255.255.255.0 is a classful IP addressing scheme.Ī 'classless' IP addressing scheme is one that uses a subnet mask to divide an IP address into smaller segments. More informationĪ 'classful' IP addressing scheme is one that does not break down an IP network into smaller segments. Creating delegated subnetted reverse lookup zones is an administrative choice only it is not solely dictated by the underlying subnetted infrastructure. Simply because your network environment is subnetted does not imply that your DNS server must be configured in the manner described in this article.

#255 255 255 0 DNS HOW TO#

This article discusses how to configure delegated subnetted reverse lookup zones for a Microsoft Windows DNS server. Conversely, as the administrator of a child domain, you now have the control necessary to make changes to both DNS host (A) records or IP address (PTR) records without having to make a request for change through the parent domain.

This flexibility in zone ownership allows you, as the administrator of a parent domain, to delegate control of both a child subdomain and a corresponding subnet of addresses to another administrator. The Internet Engineering Task Force (IETF) has created RFC 2317, 'Classless IN-ADDR.ARPA Delegation,' which discusses these considerations.ĭelegating subnetted reverse lookup zones complements the ability to delegate forward lookup zones. However, because of the inverse structure of reverse lookup zones and their strict reliance on the specific subnet structure, delegation of these zones requires special considerations. In a subnetted environment, DNS servers can easily delegate authority of forward lookup zones because they are independent of the underlying subnetted infrastructure.

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The rapid growth of the Internet community created the need to subnetwork full IP networks into smaller portions. It is recommended that you first attempt these procedures in a test environment before deploying them on a live network because of the ease with which mistakes can occur during configuration. There are numerous notes throughout this document to which you should pay close attention. It is important to understand how DNS zones work before attempting to create subnetted reverse lookup zones. Creating delegated subnetted reverse lookup zones is not a trivial task.

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