Question 1

What is CIDR notation?

Accepted Answer

CIDR (Classless Inter-Domain Routing) notation appends a slash and a number to an IP address — e.g. 192.168.1.0/24 — to show how many leading bits form the network prefix. The remaining bits identify hosts within that subnet.

Question 2

How do I calculate a subnet mask from a prefix length?

Accepted Answer

Set that many leading bits to 1 and the rest to 0, then read the result as four 8-bit groups. A /24 prefix has 24 leading 1s, giving the netmask 255.255.255.0. This calculator converts between prefix length and netmask automatically — edit either field and the other updates.

Question 3

Is my IP address sent to a server?

Accepted Answer

No. Every calculation runs locally in your browser using JavaScript. The address and prefix are only reflected in the page URL so you can share or bookmark a link — nothing is transmitted to or stored on a server.

Question 4

What's the difference between IPv4 and IPv6 addressing?

Accepted Answer

IPv4 addresses are 32 bits long (e.g. 192.168.1.1) with a maximum prefix of /32, giving about 4.3 billion addresses in total. IPv6 addresses are 128 bits long (e.g. 2001:db8::1) with a maximum prefix of /128, providing a vastly larger address space that is typically allocated in /64 subnets.

Question 5

How do I split a network into smaller subnets?

Accepted Answer

Enter the parent network and prefix, enable subnet splitting, and choose a longer prefix length. The tool lists every resulting subnet along with its network address and usable host range.