Subnet Calculator (IPv4 CDIR)
Fuld IPv4-undernet opdeling: netværk, broadcast, maske, wildcard, host range og tælle.
Resultater opdatere som du skriver.
Om denne regnemaskine
This subnet calculator turns an IPv4 address and a CIDR prefix into the full structure of a subnet. An IPv4 address is 32 bits, usually written as four dot-separated octets like 192.168.1.10, and a CIDR prefix such as /24 splits those 32 bits into a network part (the leading bits, fixed for every host in the subnet) and a host part (the remaining bits, unique to each device). This calculator takes an address and a prefix length and derives the network address, broadcast address, subnet mask, wildcard mask and the range of usable host addresses, along with the IP class and total address count.
The size of a subnet is set by the prefix: a /n block holds 2^(32−n) addresses, of which two are reserved — the network address (all host bits 0, naming the subnet) and the broadcast address (all host bits 1, reaching every host). So a /24 has 2^8 = 256 addresses and 254 usable hosts, a /25 has 128 addresses and 126 usable hosts, and each extra prefix bit halves the block. As a worked example, 192.168.1.10/24 gives a network of 192.168.1.0, a broadcast of 192.168.1.255, a 255.255.255.0 mask, a 0.0.0.255 wildcard mask, and a usable host range of 192.168.1.1 to 192.168.1.254.
Subnetting is how networks are carved into manageable, secure segments — separating departments, sizing VLANs, planning address allocation and writing firewall and routing rules. The wildcard mask (the bitwise inverse of the subnet mask) is what Cisco access-control lists and OSPF use to match ranges of addresses. The /31 and /32 prefixes are special cases: /31 is used for point-to-point links with two usable addresses and no broadcast, and /32 describes a single host.
Ofte stillede spørgsmål
Hvor mange værter er i et subnet?
A /n subnet har 2^(32−n) adresser, minus to forbeholdt netværket og broadcast. A /24 har 256 adresser og 254 anvendelige værter.
Hvad er en jokermaske?
A wildcard mask is the bitwise inverse of the subnet mask (255.255.255.0 → 0.0.0.255). Access-control lists and OSPF use it to match ranges of addresses.
Hvad er forskellen mellem netværk og broadcast adresse?
Netværksadressen (alle værtsbit 0) navngiver undernettet; broadcast- adressen (alle værtsbit 1) når frem til hver vært på den. Ingen af dem kan tildeles en enhed.
Hvad betyder CIDR-præfikset (/24, /16)?
Det er antallet af førende bits, der udgør netværket del af adressen. Et større præfiks betyder flere netværk bits og færre vært bits, så en mindre subnet: /24 giver 254 værter, /25 giver 126 og hver ekstra bit halvdelen af blokken.
Hvordan opdeler jeg et netværk i mindre undernet?
Lån værtsbits ved at øge præfikset. Opsplitning af en/24 i to 25'ere giver to blokke af 126 værter; kommer til /26 giver fire blokke af 62. Hver tilføjet præfiks bit fordobler antallet af subnet og halvdelen af deres størrelse.
Hvad er en IP-adresse klasse?
The old classful scheme split addresses by their first octet: Class A (1–126), Class B (128–191) and Class C (192–223) for unicast, plus D for multicast and E reserved. CIDR replaced classes for allocation, but the calculator still reports the class the address falls in.
Hvad anvendes /31 og /32 subnet til?
En /31 har kun to adresser og ingen udsendelse, der bruges til punkt-til-punkt links mellem routere. En /32 er en enkelt værtsadresse, fælles for loopbacks og værtsruter. Lommeregneren håndterer begge specialtilfælde.
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Slutpunkt
GET https://calculator.free/api/v1/subnet/curl
curl "https://calculator.free/api/v1/subnet/?ip=192.168.1.10&cidr=24"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/subnet/?" + new URLSearchParams({
"ip": "192.168.1.10",
"cidr": "24"
}));
const data = await r.json();
console.log(data.results);Resultaterne er skøn for generel vejledning, ikke finansiel, medicinsk eller skattemæssig rådgivning.