Tools

Small tools for everyday networking.

Things I need often enough myself and that do not deserve a sign-up form. Everything is calculated in your browser — no input ever leaves your device.

Subnet Calculator

Enter an IPv4 address and prefix: network address, host range, broadcast, subnet and wildcard mask, plus the bit boundary between network and host portion.

VLSM Planner

Split a network into subnets of differing size. Enter the demand per subnet and the allocation appears immediately, with masks, ranges and utilisation.

IPv6 Calculator

Expand and compress an IPv6 address, break down a prefix, contained /64s, reverse DNS and type — the companion to the IPv4 calculator.

CIDR Aggregation

Collapse a list of IPv4 prefixes into the smallest common set — handy when tidying up routing tables and ACLs.

Bandwidth-Delay Product

Derive the required TCP window from bandwidth and RTT — and see when window scaling becomes necessary.

Reverse DNS Zones

Build in-addr.arpa and ip6.arpa zone names and PTR records from an IP or prefix, including classless RFC 2317 delegation.