CIDR to Range

Enter CIDR notation and get the first IP, last IP, total addresses, usable hosts, and subnet mask.

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Input
Output
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About cidr to range

CIDR to Range needs nothing from a server once the page has loaded. Leave it open on a train with no signal and it carries on.

Paste a customer record into it if you need to. The record never leaves the machine you are sitting at.

You will find it under Network, alongside 17 other tools for the same sort of job.

Supports multiple CIDRs.

How to use it

01
Start it
Every control is on the tool itself. Keyboard shortcuts, where there are any, are listed beside it.
02
Watch it run
It updates in the page as you go. Nothing is sent anywhere, so it keeps working with the network off.
03
Close when done
Nothing is stored between visits. Reloading gives you a clean start rather than picking up where you left off.

Examples

Convert 10.0.0.0/24 to IP range
Get first IP, last IP, total addresses, and usable hosts for a /24 block
Input
10.0.0.0/24
Output
CIDR: 10.0.0.0/24
First IP: 10.0.0.0
Last IP: 10.0.0.255
Total addresses: 256
Usable hosts: 254
Subnet mask: 255.255.255.0
Wildcard mask: 0.0.0.255

Questions

Does CIDR to Range work offline?+

Yes. It is JavaScript running in this tab, so once the page has loaded it needs nothing further from the network. Put the machine in flight mode and it carries on. Nothing you do here is sent anywhere, because there is nowhere for it to go.

Does it remember anything between visits?+

No. Reload the page and it starts from nothing. There is no account, no saved state and no cookie holding your last session. That is a deliberate trade: it cannot lose your data because it never keeps any.

Is it accurate?+

Timing comes from performance.now(), the high resolution clock the browser provides, rather than from setInterval, which drifts by a few milliseconds every tick and compounds over minutes. What can still shift things is the browser throttling a tab in the background, so leave it visible if the timing matters.

Does it make a sound?+

Where a sound makes sense, it is generated with the Web Audio API rather than loaded as a file, so there is nothing to download and nothing to block. Browsers refuse to start audio until you have interacted with the page, which is why the first press is what switches it on.

Can I use CIDR to Range on a phone?+

Yes. The controls are sized for touch and the layout collapses to one column on a narrow screen. Bear in mind that a phone locking its screen will suspend the page, and timing stops with it.