network engineering tools

Subnets, IPv6 and links worked out in seconds.

IPv4, VLSM, route summarization, IPv6, TCP throughput, PoE and fiber calculators for people who design and run networks. Every result shows the binary math.

Your current internet IP is

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Reverse DNS: …
Provider: …
Approximate location: …

Subnet cheat sheetclick a prefix to open the full calculation

CIDR	Mask	Hosts	Wildcard
/22	255.255.252.0	1,022	0.0.3.255
/23	255.255.254.0	510	0.0.1.255
/24	255.255.255.0	254	0.0.0.255
/25	255.255.255.128	126	0.0.0.127
/26	255.255.255.192	62	0.0.0.63
/27	255.255.255.224	30	0.0.0.31
/28	255.255.255.240	14	0.0.0.15
/29	255.255.255.248	6	0.0.0.7
/30	255.255.255.252	2	0.0.0.3

subnet4 — IPv4 subnet

See the subnet table and step-by-step →

IPv4 & subnetting

subnet4IPv4 subnetNetwork ID, broadcast, host range and mask from any IP/prefix.vlsmVLSM planCarve a parent block into right-sized subnets, largest first.hosts2maskHosts → maskSmallest prefix and mask that fits a given number of hosts.summarizeRoute summarySmallest supernet covering a list of networks, with overlap check.range2cidrRange → CIDRExact CIDR blocks for any start–end IPv4 range.wildcardWildcard maskInverse mask for Cisco ACLs and OSPF, plus matched range.ipconvIP converterDotted decimal ↔ binary ↔ hex ↔ 32-bit integer.

IPv6

subnet6IPv6 subnetsHow many /56 or /64 subnets fit, with the prefixes listed.

Performance

xfer-timeTransfer timeHow long a transfer takes at a given link speed, with overhead.tcp-bdpBDP / TCP windowTCP window needed for a link, and throughput limits per flow.rate-convRate converterMbps ↔ MB/s ↔ Gbps ↔ MiB/s, bits and bytes done right.

Infrastructure

poe-budgetPoE budgetTotal PoE draw by class vs. the switch power budget.fiber-lossFiber loss budgetTotal link loss in dB and margin against the transceiver budget.