Masks, ranges and hosts. Relevant for CCNA, Network+.
Subnetting is the one skill on the CCNA and Network+ that cannot be memorised. You have to be able to take any address and any prefix length and find the network, the broadcast, the first and last host and the count, in your head, in seconds. The only way to get there is repetition with immediate correction.
Subbing generates an endless stream of subnetting questions. Easy rounds stay in the /20 to /28 range that exams love; hard rounds go anywhere from /8 to /30. A wrong answer shows the method, not just the number: the interesting octet, the block size, and where the block starts.
Twelve question types cover everything the exams ask: network and broadcast addresses, first and last usable host, usable and total addresses, subnet mask to prefix and back, wildcard masks, whether an address sits inside a subnet, address classes and private ranges.
Generated by the same code as the app. They change with every release; the app never runs out.
How to subnet fast: The block size method for IPv4 subnetting: interesting octet, block size, network, broadcast and host range in under ten seconds, with worked examples.
Find the interesting octet (the first octet of the mask that is not 255), compute the block size as 256 minus that mask octet, and round the address octet down to the nearest multiple of the block size. Everything after it becomes 0.
A /26 leaves 6 host bits, so 2^6 = 64 addresses. Minus the network and broadcast addresses that is 62 usable hosts.
Yes. Every topic and every mode is free on the web, Android and iPhone, with no account. Subbing Pro only removes ads and adds study tools such as retrying your misses.