Network
Subnetting, DNS, IP conversion and the everyday lookups network engineers do dozens of times a day. Built by someone who actually plans address space — the subnet calculator does VLSM and shows the mask boundary bit by bit.
Subnet CalculatorCalculate IPv4 subnets, masks and host ranges, split blocks (VLSM), and see the network at the bit level.DNS LookupLook up DNS records (A, AAAA, CNAME, MX, TXT, NS, CAA) for any domain, or resolve a dynamic-DNS hostname to its current IP.What Is My IPSee your public IP plus country, city, ASN and network — read at the edge, never stored.IP Address ConverterConvert an IPv4 address to its decimal, binary and hexadecimal forms and back, in your browser.IPv6 Expand / CompressExpand an IPv6 address to its full form or compress it with :: notation, both ways in your browser.URL ParserParse any URL into protocol, host, port, path, query parameters and hash, instantly in your browser.User-Agent ParserSee your own user-agent and parse any UA string into OS, browser, engine and device type.chmod CalculatorConvert Unix file permissions between checkboxes, octal (755) and symbolic (rwxr-xr-x) — kept in sync.MAC Address FormatterReformat a MAC address into colon, hyphen, Cisco dot and bare forms in upper or lower case.MTU / MSS CalculatorStack PPPoE, MAP-E/DS-Lite, GRE, WireGuard, VXLAN and IPsec (with real ESP padding) to get the effective MTU and TCP MSS, plus Cisco, YAMAHA RTX and Linux config and a DF ping to verify.Wildcard Mask CalculatorConvert a prefix or subnet mask to a wildcard mask and back, see what a non-contiguous wildcard really matches, and build Cisco ACL / OSPF network lines plus YAMAHA RTX ip filter and iptables equivalents.Route Summarization CalculatorPaste a list of IPv4 networks to get the smallest summary route, how many extra addresses it swallows, the exact minimal CIDR set, a binary alignment view, and OSPF / EIGRP / BGP / Null0 config for Cisco, YAMAHA RTX and Linux.IPv6 Subnet CalculatorCarve an IPv6 prefix such as a /48 or /56 into /64s (or any length): subnet count, addresses per subnet, a paged list, jump to subnet #N, find which subnet holds an address, nibble-boundary checks and Cisco / YAMAHA RTX / Linux config.VLSM Calculator & Config GeneratorList segments with host counts and VLANs; get a largest-first VLSM plan with gateways, usable ranges, spare capacity and free blocks, plus Cisco router-on-a-stick, L3 switch SVI, DHCP and YAMAHA RTX config and a CSV.Subnetting Practice DrillPractise subnetting against the clock: network and broadcast addresses, usable hosts and mask ⇄ prefix, with the block-size explanation after every answer, personal bests and a shareable challenge link with the same questions.Port Number QuizLearn common TCP/UDP port numbers with a 10-question timed quiz: port → service, service → port or mixed, three difficulty pools from 15 essentials to 66 ports, explanations, personal bests and a shareable challenge link.Binary & Hex Conversion DrillPractise converting between binary, decimal and hexadecimal in six directions at 4, 8 or 16 bits, with place-value and nibble explanations, personal bests and a shareable challenge link with the same numbers.