Small Network DNS Zone File Generator

Small Network DNS
Zone File Generator

About Subnets [ more... ]

All true subnets are standalone, meaning their gateway and broadcast addresses are within their allocated address space. They also begin on a number that is evenly divisible by the number of addresses assigned. A /28 network has 4 bits of address space (all IP addresses have 32 bits. By subtracting the prefix, the / part, you get the number of bits in your network. Here that's 32 - 28, or 4 bits). The total number of possible addresses is 2 raised to the number-of-bits. In this case that's 24 or 16 addresses. This subnet address would begin on a multiple of 16.

Just like running a business networks have a certain amount of overhead - with networks that is always 3 addresses: network, gateway, and broadcast. For example, your ISP tells you that there are 5 useable addresses in your subnet. Add 3 (the overhead) and that is 8 total. Expressed exponentially 8 = 23. 32 - 3 = 29. You have received a /29 subnet from your provider. The network address is always the first one (all bits off). The broadcast address is always the last one (all bits on). The gateway is usually the address immediately after the network IP or immediately before the broadcast IP.

About Address Blocks [ more... ]

Block addressing is very simple. You are sharing a subnet with somebody else. That somebody else is the owner and has the network, gateway, and broadcast addresses. They are also the authoritative owner of the network. Because you cannot also claim to be the authority for that network space an alternative method of publishing your data needs to be found. In this situation the owner will delegate each of your addresses to you. That means that rather than publish a single glue record pointing to your nameservers as authoritative for a zone beginning at some address they will publish one for each of your addresses. On your end you publish full records sets with SOA and NS for each of your addresses. Results: slightly greater number of records, same ability to publish your own ownership information. Unlike a true subnet every one of your addresses is useable.