Kernaali ToolsIPv4 Subnet Calculator
Find the network, broadcast, mask and usable address range for an IPv4 prefix.
Network calculators & references
From a single subnet to a full link budget. Choose a task, enter your values and inspect the assumptions before making a change.
25 tools and references
Address planning
CIDR to Netmask Converter
Convert an IPv4 prefix length into a contiguous dotted-decimal subnet mask.
Netmask to CIDR Converter
Validate an IPv4 subnet mask and recover its prefix length.
Wildcard Mask Calculator
Convert between a contiguous subnet mask and its inverse ACL wildcard.
IP Range to CIDR Converter
Cover an inclusive IPv4 range with the smallest exact set of CIDR blocks.
CIDR Aggregation Calculator
Merge overlapping and adjacent IPv4 routes without adding unlisted address space.
Subnet Splitter
Divide one IPv4 parent network into equal-size child subnets.
VLSM Calculator
Allocate different-size IPv4 LAN subnets from a parent network.
IPv6 Subnet Calculator
Calculate an IPv6 network boundary, final address and exact address-space size.
IPv6 Address Expander and Compressor
Normalize IPv6 text and inspect all eight hexadecimal groups.
Reverse DNS / PTR Converter
Build IPv4 host reverse names and IPv6 host or nibble-aligned reverse-zone names.
Link & transport
TCP MSS Calculator
Estimate TCP MSS and the payload budget after selected header options.
MTU Budget Calculator
Subtract a known encapsulation allowance and estimate an ICMP echo data budget.
IPsec / ESP Overhead Calculator
Calculate ESP expansion for a specific packet, cipher and encapsulation model.
Bandwidth and Transfer Time Calculator
Estimate file transfer duration with explicit file units and useful-throughput efficiency.
Bandwidth-Delay Product Calculator
Estimate bytes in flight from bottleneck bandwidth and round-trip delay.
Packets Per Second / Line Rate Calculator
Estimate Ethernet packet rate including preamble and interframe spacing.
Fiber Optic Link Budget Calculator
Estimate optical path loss and spare margin from your transceiver and cable specifications.
dBm / mW Converter
Convert logarithmic power in dBm to milliwatts and back.
VLAN / Ethernet Frame Overhead Calculator
Calculate Ethernet frame size, tag cost, padding and payload efficiency.
References
IPv4 Subnet / CIDR Cheat Sheet
A printable /0–/32 table of IPv4 masks, block sizes and ordinary usable address counts.
Subnetting Cheat Sheet
Work through original subnetting examples for boundaries, host capacity and address allocation.
Special and Private IP Address Reference
Recognize common private, shared, loopback, documentation and local address ranges.
Common Network Ports Reference
A curated, printable guide to common service ports and transport choices.
DNS Record Cheat Sheet
Understand common DNS record types, TTLs and frequent configuration mistakes.