DNS & DHCP Planner — IT Ops Tools

Subnet & scope

Subnet (CIDR)

Gateway

Custom gateway

Static / infra reserve

Lease (hours)

Pool start (optional)

Pool end (optional)

Exclusions

The static reserve is carved off the low end (and includes the gateway); the DHCP pool fills the rest. Leave pool start/end on auto to derive them, or set them by hand. Exclusions are single IPs or start-end ranges, comma or line separated.

Examples:

Add a reservation

Bind a fixed IP to a MAC address (and optional hostname). Conflicts — duplicates, out-of-subnet, network/broadcast — are flagged instantly.

IP address

MAC (optional)

Hostname (optional)

Add sample:

IP	MAC	Hostname	Status

How the DNS & DHCP Planner works

One shared plan drives four views — scope, map, DNS and export — so a subnet turns into a working address plan and ready-to-paste server config without anything leaving your browser.

DHCP Scope Planning

Enter a subnet in CIDR notation and get the gateway, a static/infrastructure reserve, the DHCP pool range, and pool size after exclusions — with utilisation and lease-time guidance so you don't under- or over-provision.

Visual IP & Reservation Map

See every address in the subnet colour-coded by role — network, gateway, static, pool, excluded and reserved — as a grid for smaller networks or a proportional band for large ones, so gaps and overlaps are obvious at a glance.

Reservations with Conflict Detection

Bind IPs to MAC addresses and hostnames and get instant validation: duplicate IPs or MACs, addresses outside the subnet, network/broadcast collisions and malformed hostnames are all flagged before they reach a live DHCP server.

Matching DNS Records

Every named reservation produces a forward A record and a matching PTR record in the correct in-addr.arpa reverse zone, output as copy-ready BIND zone files complete with SOA and NS stubs.

Server-Ready Exports

Download the whole plan as an ISC dhcpd.conf subnet block, a Windows netsh DHCP script, BIND forward and reverse zone files, or a CSV of reservations — ready to drop into your provisioning workflow.

Runs Entirely in Your Browser

All planning, validation and file generation happen client-side in JavaScript. Nothing you type is sent to a server, logged or stored — safe to use with real internal address plans, MAC addresses and hostnames.

Frequently asked questions

How do I size a DHCP pool for a subnet?

Start from the usable host range, carve off a static block at the low end for the gateway, servers, printers and other fixed devices, then let the DHCP pool take the rest. A /24 gives 254 usable addresses; reserving the first 10 for infrastructure leaves a 244-address pool. The planner does this automatically and lets you adjust the static count, pool bounds and exclusions.

What is the difference between a DHCP reservation and an exclusion?

A reservation always hands the same IP to a specific MAC address, so a device inside the pool range gets a predictable address. An exclusion removes addresses from the pool so DHCP never leases them — used when a static device sits inside the pool range. Reserve when you want DHCP to manage the lease; exclude when the device is configured statically.

How does the tool generate PTR (reverse DNS) records?

For every reservation that has a valid hostname, it emits a forward A record (host.domain → IP) and a matching PTR record grouped into the correct in-addr.arpa reverse zone based on the address's first three octets. You can copy the BIND-format forward and reverse zones or download them as zone files.

What lease time should I use?

A 24-hour lease is a sensible default for a stable office LAN. Use shorter leases (2–8 hours) on small or busy pools, guest networks, or anywhere devices come and go frequently, so addresses recycle quickly. The planner flags when a pool is filling up and a shorter lease would help.

Is anything I enter sent to a server?

No. Every calculation — the scope plan, the IP map, conflict detection and all exports — runs entirely in your browser in JavaScript. Nothing you type is uploaded, logged or stored, so it is safe to use with real internal addressing, MAC addresses and hostnames.