This is a very useful subnetting chart that will help out a student of Cisco networking. This shows how many subnets you can have with a certain subnet mask. This can be tricky to learn and something like this will really help out.
![Subnetting cheat sheet.](https://www.securitronlinux.com/wp-content/uploads/2015/05/subnet.png)
Another way to calculate subnetting is with the sipcalc command for Linux. This will calculate all of the subnets for a certain address and subnet mask.
Here is an example.
ubuntu ~/nt $ sipcalc 192.168.0.1/26 -[ipv4 : 192.168.0.1/26] - 0 [CIDR] Host address - 192.168.0.1 Host address (decimal) - 3232235521 Host address (hex) - C0A80001 Network address - 192.168.0.0 Network mask - 255.255.255.192 Network mask (bits) - 26 Network mask (hex) - FFFFFFC0 Broadcast address - 192.168.0.63 Cisco wildcard - 0.0.0.63 Addresses in network - 64 Network range - 192.168.0.0 - 192.168.0.63 Usable range - 192.168.0.1 - 192.168.0.62 |
This makes subnet calculation very easy indeed.
A lot more information on subnetting and more charts here: http://www.cisco.com/c/en/us/support/docs/ip/routing-information-protocol-rip/13790-8.html.
IPv6 subnetting information: http://en.linuxreviews.org/IPv6_subnet_matrix_table.