Besides resurrecting a thread almost a year old I don't think that I understand anything that you've posted
ordabis wrote:I've figured out subnetting by taking the block size from the subnets CIDR and dividing the host part of the IP address by the block size. Then multiply the block size by the sum to get the subnet address.
Seriously!
ordabis wrote:If I need to figure out the subnet for 10.99.185.236/20
I know that a /20 is a block size of 16.
/20 means that the first 20 bits are the network portion of the address. That leaves 12 bits in the host portion of which up to 8 of the highest order can be used to increase the prefix to create subnets.
What's "block size" mean?
ordabis wrote:I started writing out counting in the different block sizes and found common reference points to help hop along, like 10's. A block size of 8 if I'm looking for a subnet in the 200's 8x20=160 and 8x30=240. After that picking up the count is a little easier.
Easier for whom?
ordabis wrote:The valid hosts and subnet values can be easily figured by mastering your powers of 2 table.
A /20 is always going to have a 2 to the 12th calculating the host portion and a 2 to the 4th calculating the subnet portion (of course - 2).
Totally baffling I'm afraid

And you do not subtract 2 from the number of subnets, you subtract 2 from the number of addresses.
ordabis wrote:If you build a table that combines your CIDR, subnet mask, block size increment and powers of 2 values you'll engrain a cheat sheet in your head that can help you master subnetting in your head.
Some of the binary solutions were confusing to me and take way too long to convert.
Not for me. I find the that doing the binary conversion is straightforward - why learn another complex method?
Hmm, ok, maybe I might get what your saying - if you assume a Class C network with a /20 then you have 4 subnet bits that gives you 16 subnets - is that what you mean by "block size"??
The only problem with that is default classful addressing disappeared from the CCNA in 2004/2005 and these days is just a historic relic from another era.
Aubrey
The illiterate of the 21st century will not be those who cannot read and write, but those who cannot learn, unlearn, and relearn. Alvin Toffler, "Future Shock" 1970