mrnx/network

IPv4 subnet calculator

Type an address with a prefix or a dotted mask. Click any value to copy it.

Examples
IPv4 subnet calculatorNetwork, broadcast, host range, binary view and subnet splitting.VLSM plannerCarve an address block into right-sized subnets from host counts.CIDR aggregationMerge and deduplicate prefix lists for ACLs, firewalls and route summaries.Wildcard mask calculatorConvert masks and wildcards, see exactly which addresses a wildcard matches and find one wildcard for a set of hosts.IPv6 calculatorCompress, expand, classify and subnet IPv6 prefixes.IP ↔ hex & DHCP option 43Convert IPs to hex, decimal and binary, build or decode option 43 for wireless controller discovery.
Domain health reportOne graded report for a domain: name servers, SOA, DNSSEC, CAA, MX, SPF, DMARC, DKIM and MTA-STS.DNS lookupAll common record types for a name in one go, with TTLs, DNSSEC status and reverse lookups.SPF / DMARC / DKIM checkerLook up or paste email authentication records and get them validated and explained.Email header analyzerTrace a message hop by hop with delays, see SPF/DKIM/DMARC results and spot spoofing signs.
What's my IPYour public IP address as the internet sees it, plus what your browser reveals.IP, ASN & WHOIS lookupOwner, prefix, origin AS, RPKI status and abuse contact for an IP; prefixes for an AS; registration for a domain.Bulk IP extractor & enrichmentPull every IP out of a log, count and classify them, then add owner, AS, country and Tor-exit status.Bulk MAC vendor lookupPaste a MAC/ARP table or any text; every MAC is found and matched to its vendor.
Config template generatorFill a config template with {{ placeholders }} from a spreadsheet: one block per port, VLAN, firewall object or switch.ACL builderBuild Cisco IOS access lists from plain input (CIDR, port lists, ranges) with correct wildcards, then send them to the tester.ACL testerPaste a Cisco IOS ACL, test a packet against it and find shadowed or redundant rules.Prefix list creator & testerTest which entry of a BGP prefix list a route hits, spot dead entries, or generate lists for IOS, IOS XR and Junos.BGP toolkitTest AS-path regexes, decode communities (no-export, blackhole, route targets) and convert or classify AS numbers.VLAN list calculatorCompare, compress and expand trunk VLAN lists and get the add / remove commands for each vendor.
Packet capture analyzerDrop a .pcap / .pcapng: talkers, TCP retransmissions and resets, DNS, DHCP, TLS, ARP and STP problems, analysed in your browser.Config & state diffCompare configs or full show-command backups: see interfaces that went down, lost neighbors, moved MACs, and get draft config commands.MTU & MSS calculatorStack tunnels (GRE, IPsec, VXLAN, WireGuard, PPPoE, MPLS) to get the inner MTU, TCP MSS clamp and DF ping tests.Bandwidth & throughputLive copy progress, transfer times, TCP window limits, TB vs TiB and latency from distance.Signal & link budgetdBm to mW, Wi-Fi signal through walls, free-space path loss and fibre optical power budget.
Certificate decoderDecode PEM certificates and chains: SANs, validity, key size, extensions and fingerprints.JWT decoderDecode a JSON Web Token, read its claims and expiry, spot risky settings and check HMAC signatures.Password & key generatorStrong random passwords, Wi-Fi keys, hex/base64 secrets and UUIDs, with entropy and crack-time estimates.Encoders & convertersBase64, URL and hex encoding, SHA hashes, Unix timestamps, punycode domains and a chmod calculator.
Subnet cheat sheetEvery prefix length with mask, wildcard and host count, plus reserved ranges and IPv6 sizes.Port referenceSearchable list of common ports and protocols with security notes.DSCP & QoS referenceDSCP, ToS byte, precedence, CoS and Wi-Fi classes side by side, with capture filters and marking commands.Network command referenceCommands by task for Cisco, Arista, Aruba, Juniper, Huawei, MikroTik, Fortinet (switch, FortiGate) and Palo Alto, side by side.

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