What to jot down on paper for subnetting?

sleemie

I've asked this before and didn't get a response, but i'm wondering what I should memorize to jot down at the beginning of the test for subnetting.

I was thinking that if you memorize certain factors of two, such as 2^10 and 2^20 and use those as a starting base to figure the rest and you know the 256-x (x being the mask) to determine the increments of the host IDs and the constants, 16, 48, 80, 96, 112, 144, 160, 176, 192, 224.....do you really need to write anything down? can't you pretty much figure out most subnet problems within like 1 minute and a half or so just by having this information in your head?

keenon

you should jot down the major subnet points.

128,64,32,16,8,4,2,1

then also the masks

0,128, 192, 224, 240,248, 252,254(31), 255(32)

then how many host per mask

254, 126, 62, 30, 14, 6, 2, 1( i'm not sure if they started counting a /31 although theres an RFC for it)

then amount of networks per mask