I swear it. Subnetting is the worst.
One of the few reasons that helped me leave working on my CCNA.
No matter if it was an instructor, learntosubnet.com, scratch on the internet.
NOTHING and no body has been able to help me out with subnetting until this post.
I understood a bit but never could really grasp it.
Well im not studying 291 and have to face subnetting again which really kills me. I would really like to come back, get my MCSE and CCNA after.
I just wanted to thank Agustin........ for this great help.
Well, this is how to make it quick (not sure if this is the best but, works for me):
Learn this scale (1): 2 4 8 16 32 64 128 256 512 1024 2048 4096 8192
And this one (2): 128 192 224 240 248 252 254 255
now, to your question:
/28 would be: 11110000
number of subnets: how many 1s you have? 4? good... what number is in position 4 on scale 1?: 16.
Number of hosts: How many 0s you have? 4 again? good... what number is in position 4 on scale 1?: 16... warning: remember to substract 2 ips... 14.
What is the subnet mask?: 4th place of scale 2: 255.255.255.240
And what is the IP block?: look at scale 1, 4th place: 16 IP blocks (remember, as Alien said, if ip subnet-zero is on, start from 0 always).
This at least works for me... and lets you subnet in your head quite easy.
Also, the scale works for subnetting any class A B or C.
