ipcalc

Install sipcalc and ipcalc

Use apt-get command:
$ sudo apt-get install sipcalc ipcalc
Please note that ipcalc is installed by default under RHEL / CentOS / Fedora Linux using initscripts package.

Examples

Let us see how to calculate subnets for 192.168.0.1/24:
$ ipcalc 192.168.0.1/24
Output:

Address:   192.168.0.1          11000000.10101000.00000000. 00000001
Netmask:   255.255.255.0 = 24   11111111.11111111.11111111. 00000000
Wildcard:  0.0.0.255            00000000.00000000.00000000. 11111111
=>
Network:   192.168.0.0/24       11000000.10101000.00000000. 00000000
HostMin:   192.168.0.1          11000000.10101000.00000000. 00000001
HostMax:   192.168.0.254        11000000.10101000.00000000. 11111110
Broadcast: 192.168.0.255        11000000.10101000.00000000. 11111111
Hosts/Net: 254                   Class C, Private Internet

You can also try sipcalc:
$ sipcalc 192.168.0.1/24
Output:

-[ipv4 : 192.168.0.1/24] - 0
[CIDR]
Host address            - 192.168.0.1
Host address (decimal)  - 3232235521
Host address (hex)      - C0A80001
Network address         - 192.168.0.0
Network mask            - 255.255.255.0
Network mask (bits)     - 24
Network mask (hex)      - FFFFFF00
Broadcast address       - 192.168.0.255
Cisco wildcard          - 0.0.0.255
Addresses in network    - 256
Network range           - 192.168.0.0 - 192.168.0.255
Usable range            - 192.168.0.1 - 192.168.0.254

More examples:

$ sipcalc 192.168.0.1 255.255.128.0 255.255.192.0
Output:

-[ipv4 : 192.168.0.1 255.255.128.0] - 0
[CIDR]
Host address            - 192.168.0.1
Host address (decimal)  - 3232235521
Host address (hex)      - C0A80001
Network address         - 192.168.0.0
Network mask            - 255.255.128.0
Network mask (bits)     - 17
Network mask (hex)      - FFFF8000
Broadcast address       - 192.168.127.255
Cisco wildcard          - 0.0.127.255
Addresses in network    - 32768
Network range           - 192.168.0.0 - 192.168.127.255
Usable range            - 192.168.0.1 - 192.168.127.254
-
-[ipv4 : 255.255.192.0] - 0
[CIDR]
Host address            - 255.255.192.0
Host address (decimal)  - 4294950912
Host address (hex)      - FFFFC000
Network address         - 255.255.192.0
Network mask            - 255.255.255.255
Network mask (bits)     - 32
Network mask (hex)      - FFFFFFFF
Broadcast address       - 255.255.192.0
Cisco wildcard          - 0.0.0.0
Addresses in network    - 1
Network range           - 255.255.192.0 - 255.255.192.0

Display results as HTML

$ ipcalc -h 192.168.0.1/255.255.128.0

For more options, please refer to man page:
$ man ipcalc
$ man sipcalc

ipcalc: ip address expected
Usage: ipcalc [OPTION…]
-c, –check Validate IP address for specified address family
-4, –ipv4 IPv4 address family (default)
-6, –ipv6 IPv6 address family
-b, –broadcast Display calculated broadcast address
-h, –hostname Show hostname determined via DNS
-m, –netmask Display default netmask for IP (class A, B, or C)
-n, –network Display network address
-p, –prefix Display network prefix
-s, –silent Don’t ever display error messages

Help options:
-?, –help Show this help message
–usage Display brief usage message
# which ipcalc
/bin/ipcalc
# rpm -qf /bin/ipcalc
initscripts-8.45.30-2.el5