Is my addressing plan uploaded?

No. Every tool on this page performs arithmetic in your browser. There is no upload step and no server that could receive a plan.

Why does your subnet calculator say a /31 has two usable addresses?

Because RFC 3021 defines a /31 as a point-to-point link with two usable addresses and no broadcast. Calculators reporting zero disagree with the routers people actually configure.

Will there be DNS and TLS tools?

DNS, mail-record and registration lookups are planned and can run from the browser against public resolvers. They will say plainly what is sent and where. Certificate and HTTP header inspection cannot be done from a browser at all, so those need a server and are not promised yet.

The VLSM Designer exports CSV and JSON, generated in your browser. More tools will gain exports as the vertical grows.

Networking tools that run on your machine

Subnetting, addressing plans and network design, calculated in your browser. Your addressing plan is not something to hand to a website, so these tools do not ask for it.

Home › Networking

Local toolsEverything on this page is arithmetic performed by your browser. No addressing plan, topology or hostname is uploaded, and there is no server that could receive one.

The whole design

Where the pieces have to agree with each other.

Network Architecture DesignerDevices, links, VLANs and addressing in one project, checked by every rule the other tools use and exported as a document you keep.Flagship

IP & subnetting

Address arithmetic, done once and shared by every tool here.

Subnet CalculatorNetwork, broadcast, usable range, mask and wildcard, with the network and host bits shown. IPv4 and IPv6.Start here VLSM DesignerGive it host counts per segment and it packs the parent network without gaps, sizing for growth and saying what did not fit.Flagship CIDR Range CalculatorA prefix in, its boundaries out — first, last, how many, what it splits into and what it sits inside. IP Range to CIDRTwo addresses in, the smallest exact set of prefixes out. Never covers an address you did not ask for.Exact CIDR AggregatorMerges a list down to the smallest equivalent set, and refuses to merge prefixes that only look adjacent. IPv6 VisualizerExpand, compress and explain — including why a single zero group is never written as a double colon.RFC 5952

VLAN & segmentation

Broadcast domains, the addressing that goes with them, and the misconfigurations that join two networks silently.

VLAN + Subnet DesignerName your VLANs and say how many devices each holds. It allocates subnets, proposes gateways and DHCP pools, then checks the plan for what actually breaks networks.Flagship VLAN PlannerFor a scheme you already run. Write down what is really there and find the overlaps, bad gateways and DHCP pools that cover a router. VLAN Trunk VisualizerWatch a tag added and removed across a trunk — and what a native VLAN mismatch does to a frame when neither switch logs anything.Teaching IPv6 Subnet PlannerDivide a delegated prefix into subnets. Counts subnets rather than hosts, because host counts do not constrain an IPv6 plan.

Address management

Somewhere to keep the plan, and the separate routing tables it may live in.

IPAM LiteSubnets, gateways, DHCP scopes and the static assignments everyone forgets — validated as you type and saved to a file you control.Flagship VRF PlannerSeparate routing tables, their route targets, and a matrix of who can actually reach whom — including the reachability nobody intended.

Routing

Where traffic actually goes, and why a router chose that and not the other one.

OSPF Area DesignerRouters, areas and link costs in; shortest paths, equal-cost splits and the area faults that stop OSPF working out. OSPF Cost CalculatorCost from bandwidth, and which link speeds become indistinguishable at the reference bandwidth almost nobody changed. BGP Best-Path SimulatorCandidate routes in, the winner out, and the step that decided it — including the MED comparison that catches everyone.Step by step AS-Path VisualizerLength as BGP counts it, prepending, loops and private ASNs — and why an AS_SET counts as one entry. BGP Community BuilderStandard and large communities parsed and named, with the well-known values recognised.

MPLS & segment routing

Label switching, and the arithmetic that replaced a protocol.

MPLS Label Stack VisualizerA packet hop by hop: labels pushed, swapped and popped, and why the VPN label survives penultimate hop popping.Very high MTU & Encapsulation CalculatorStack up what a packet is wrapped in and see the overhead, the payload left, and the underlay MTU a full packet really needs. SRGB & Prefix-SID PlannerPlan SRGBs and prefix SIDs, and build a segment list into a label stack. Catches duplicate SIDs and inconsistent ranges. MPLS to SR Migration PlannerModel a staged move from LDP to segment routing and find the stage where transport would break.

Fabrics & infrastructure

Data centre fabrics, and the things that make an office network work or not.

EVPN/VXLAN Fabric DesignerLeaf-spine design with underlay and overlay views, checking Clos rules, VTEPs, the VNI plan and the MTU that VXLAN quietly needs.Flagship PoE Power Budget CalculatorWhat your powered devices reserve against what the switch actually has — which is set by its power supply, not its port count. Camera Network & Storage PlannerBandwidth and retention storage worked out from the bitrate you set, because resolution alone decides neither. Wi-Fi Channel & Capacity PlannerWhich channels your regulator allows, how many are genuinely clear at each width, and how many access points a room full of people needs. Bandwidth & Bottleneck PlannerRealistic concurrent demand rather than the total nobody reaches, and the narrowest hop that decides a path whatever the rest can do.

DNS & mail

The first tools here that have to ask somebody. They say exactly what is sent.

Email DNS AnalyzerMX, SPF, DMARC and DKIM, with the ten-lookup limit counted through nested includes and every finding explained in plain terms.Network request DNS InspectorA domain's records with their TTLs and DNSSEC status, looked up by your browser rather than through us.Network request

What is not here

The vertical the brief laid out is built. What is not here, and will not be without a server: certificate details, HTTP response headers, redirect chains and protocol negotiation. A browser cannot read another origin's headers or its peer certificate, so those would need a backend rather than a promise.

On the tools that ask somebody. The DNS and mail tools genuinely cannot answer their question without a lookup, so they carry a different badge and say exactly what is sent: the domain name, to a resolver you pick, straight from your browser. Toolsfully has no server in the path and never sees the query. Everything else on this page is arithmetic and touches nothing. A handful of checks — certificate details, HTTP response headers, redirect chains — cannot be done from a browser at all and would need a server; those are being weighed rather than faked.

The rule these tools are built on

An addressing plan describes where things are and how to reach them. It is exactly the document you would not paste into an unfamiliar website, and most free subnet calculators are websites you paste it into.

Everything here is arithmetic, and arithmetic does not need a server. The shared IP engine behind these pages is tested against the cases where calculators usually disagree with real equipment: a /31 has two usable addresses because RFC 3021 says so, a /32 is a single host route, IPv6 has no broadcast address to subtract, and a mask like 255.255.0.255 is refused rather than quietly interpreted.