calculator de subrețea

IP Address / (CIDR or Netmask)

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Classful Network

Class	Leading bits	Host Address Range	Number of Networks	Notation CIDR	Default Netmask
Class A	0	0.0.0.0 - 127.255.255.255	128	/8	255.0.0.0
Class B	10	128.0.0.0 - 191.255.255.255	16384	/16	255.255.0.0
Class C	110	192.0.0.0 - 223.255.255.255	2097152	/24	255.255.255.0
Class D (multicast)	1110	224.0.0.0 - 239.255.255.255	not defined		not defined
Class E (reserved)	1111	240.0.0.0 - 255.255.255.255	not defined		not defined

Non-routable networks

10.0.0.0 to 10.255.255.255 (10/8 prefix)
172.16.0.0 to 172.31.255.255 (172.16 / 12 prefix)
192.168.0.0 to 192.168.255.255 (192.168 / 16 prefix)
Special cases
127.0.0.0 to 127.255.255.255 (LoopBack)
169.254.0.0 to 169.254.255.255 (undeclared hosts)
224.0.0.0 to 239.255.255.255 (Multicast)

This ip address calculator takes IPv4 address and subnet mask or CIDR then calculates and converts to binary ip address, the network address, broadcast address (broadcast), inverse netmask (Cisco wildcard mask), CIDR(Mask Bits), network mask, number of hosts, maximum number of sub-networks, ip range calculator : first and last host address. It is also intended to be a very good educational tool to verify the results and understand the binary values.

Reference : wikipedia: classful network